1

4.7 INFLUENZA 1

4.7.1 Virology 2

The influenza viruses are single-stranded RNA orthomyxoviruses. They are classified antigenically as types A, B or C, 3

but only influenza A and B are clinically important in human disease.1 Influenza viruses possess two surface 4

glycoprotein antigens: the haemagglutinin (H), which is involved in cell attachment during infection, and the 5

neuraminidase (N), which facilitates the release of newly synthesised virus from the cell. Influenza A viruses can be 6

classified into subtypes based on differences in these surface antigens, whereas influenza B cannot. Antibody against 7

the surface antigens, particularly the haemagglutinin, reduces infection or severe illness due to influenza. 8

Both influenza A and influenza B viruses undergo frequent changes in their surface antigens, involving stepwise 9

mutations of genes coding for H and N glycoproteins. This results in cumulative changes in influenza antigens, or 10

‘antigenic drift’, which is responsible for the annual outbreaks and epidemics of influenza and is the reason that the 11

composition of influenza vaccines requires annual review. ‘Antigenic shift’, defined as a dramatic change in influenza 12

A H (and other) antigen, occurs occasionally and unpredictably and can cause pandemic influenza.1 Pandemic subtypes 13

arise following antigenic shift, which is due to direct adaptation to humans of an avian or animal virus, or to this 14

adaptation occurring by genetic reassortment (mixing) with a human virus. 15

4.7.2 Clinical features 16

Influenza is transmitted from person to person by virus-containing respiratory aerosols produced during coughing or 17

sneezing, or by direct contact with respiratory secretions.1,2

Influenza virus infection causes a wide spectrum of disease, 18

from no or minimal symptoms, to respiratory illness with systemic features, to multisystem complications and death 19

from primary viral or secondary bacterial pneumonia. Severe disease is more likely with advanced age; lack of previous 20

exposure to antigenically related influenza virus; greater virulence of the viral strain; chronic conditions, such as heart 21

or lung disease, renal failure, diabetes and chronic neurological conditions; immunocompromise; obesity (class III); 22

pregnancy; and smoking. In pandemics, severe disease may also occur in otherwise healthy young adults. Annual attack 23

rates in the general community are typically 5 to 10%, but may be up to 20% in some years. In households and ‘closed’ 24

populations, attack rates may be 2 to 3 times higher.3,4

However, as asymptomatic or mild influenza illness is common 25

and symptoms are non-specific, a large proportion of influenza infections are not detected. 26

In adults, the onset of illness due to influenza is often abrupt, usually after an incubation period of 1 to 3 days, and 27

includes systemic features such as malaise, feverishness, chills, headache, anorexia and myalgia. These may be 28

accompanied by a cough, nasal discharge and sneezing. Fever is a prominent sign of infection and peaks at the height of 29

the systemic illness. Symptoms are similar for influenza A and B viruses. However, infections due to influenza A 30

(H3N2) strains are more likely to lead to severe morbidity and increased mortality than influenza B or seasonal 31

influenza A (H1N1) strains.1,2

32

The clinical features of influenza in infants and children are similar to those in adults. However, temperatures may be 33

higher in children (and may result in febrile convulsions in this susceptible age group), and otitis media and 34

gastrointestinal manifestations are more prominent.5 Infection in young infants may be associated with more non-35

specific symptoms.5,6

36

Complications of influenza include: acute bronchitis, croup, acute otitis media, pneumonia (both primary viral and 37

secondary bacterial pneumonia), cardiovascular complications including myocarditis and pericarditis, post-infectious 38

encephalitis, Reye syndrome, and various haematological abnormalities. Primary viral pneumonia occurs rarely, but 39

secondary bacterial pneumonia is a frequent complication in persons whose medical condition makes them vulnerable 40

to the disease. Such persons are at high risk in epidemics and may die of pneumonia or cardiac decompensation. 41

4.7.3 Epidemiology 42

In most years, minor or major epidemics of type A or type B influenza occur, usually during the winter months in 43

temperate regions. In Australia, although an average of 85 deaths and approximately 4000 hospitalisations directly 44

attributed to influenza are notified annually, it has long been recognised that this is a substantial underestimate of the 45

impact of influenza.7 It is estimated that there are an average of over 13 500 hospitalisations due to influenza per year in 46

Australia and over 3000 deaths per year in Australians aged over 50 years alone.8 Influenza activity varies from year to 47

year and is dependent on the circulating virus and the susceptibility of the population.8,9

For example, there were over 48

10 000 confirmed cases of influenza reported to the National Notifiable Diseases Surveillance System in the first half of 49

2011, compared with approximately 1570 for the same period in 2010.2 Laboratory testing for influenza has also 50

increased in recent years. In Australia, like other developed countries, the highest influenza burden is seen in the elderly 51

and in children <5 years of age (Figure 4.7.1).9-11

During annual epidemics of influenza, mortality rises, especially 52

2

among the elderly and people with chronic diseases, and there is increased morbidity, increased rates of hospitalisation 1

for pneumonia, and exacerbation of chronic diseases in association with influenza.12,13

2

Figure 4.7.1: Influenza notification rates 2006–2007* and hospitalisation rates 2005–2007,* Australia, by age 3

group9 4

5

* Notifications where the month of diagnosis was between January 2006 and December 2007; hospitalisations where the month of separation was 6 between July 2005 and 30 June 2007. These data are prior to the appearance of the pandemic A(H1N1)pdm09 virus in 2009. 7

Three pandemics were recognised in the 20th century, in 1918 (H1N1), 1957 (H2N2) and 1968 (H3N2). Each of these 8

pandemic strains replaced the previously circulating influenza A subtype and went on to circulate as seasonal influenza. 9

In 1977, the A (H1N1) re-emerged in the human population and, since then, A (H1N1) and A (H3N2) have co-10

circulated with influenza B. Recently, the avian influenza A virus subtypes, H5N1 and H9N2, have caused human 11

infections. The most notable of these is the A (H5N1) subtype, which has become established in domestic poultry 12

throughout Southeast Asia and has spread to Europe and Africa in either wild birds or domestic poultry. Although 13

growing numbers of people have contracted the virus by contact with birds and there is a high mortality rate (≥50%), 14

there has been no evidence of ongoing person-to-person transmission. 15

In 2009, the World Health Organization (WHO) declared a pandemic of a novel subtype A (H1N1) influenza virus, 16

A(H1N1)pdm09, which originated in swine; the pandemic started in Mexico and the United States in April 2009. In 17

August 2010 the WHO reported that more than 214 countries and overseas territories or communities reported 18

laboratory-confirmed cases of A(H1N1)pdm09 (pH1N1) influenza, including more than 18 000 deaths.14

In Australia, a 19

total of 44 403 confirmed cases of pH1N1 influenza occurred between May 2009 and November 2010, including 6767 20

cases in 2010. A total of 213 pandemic influenza-associated deaths were reported, 22 of which occurred in 2010.15

21

Evidence from multiple outbreak sites demonstrated that the A(H1N1)pdm09 virus rapidly established itself and was 22

the dominant influenza strain in most parts of the world. The clinical picture of pH1N1 influenza appeared to be largely 23

consistent across all countries, with most affected persons experiencing moderate illness. Risk factors for severe disease 24

included obesity, pregnancy, diabetes mellitus and, in Australia, being of Aboriginal or Torres Strait Islander descent 25

(see 3.1 Vaccination for Aboriginal and Torres Strait Islander people). Although influenza can cause very severe and 26

fatal illness, particularly in the elderly, the impact of pH1N1 influenza in younger healthy adults and in pregnant 27

women was proportionally greater than normal seasonal outbreaks, even though the absolute number of such cases 28

remained low. During the last quarter of 2009, Australia introduced a non-adjuvanted, inactivated, egg-derived, 29

monovalent A(H1N1)pdm09 vaccine for administration to all persons aged ≥6 months (Panvax, CSL Limited). Expired 30

monovalent vaccine supplies were withdrawn in December 2010.16

In Australia, there was ongoing summer activity of 31

3

A(H1N1)pdm09 in late 2009, and the virus continued to circulate in 2010 and 2011, replacing the previously circulating 1

seasonal H1N1 strain.2 The A(H1N1)pdm09 strain has been included in trivalent seasonal influenza vaccine 2

formulations used in the southern hemisphere since 2010. 3

4.7.4 Vaccines 4

The administration of influenza vaccine to persons at risk of complications of infection is the single most important 5

measure in preventing or attenuating influenza infection and preventing mortality. After vaccination, most adults 6

develop antibody levels that are likely to protect them against the strains of virus represented in the vaccine. In addition, 7

there is likely to be protection against many related influenza variants. Infants, the very elderly, and persons who are 8

immunocompromised may develop lower post-vaccination antibody levels. Under these circumstances, influenza 9

vaccine may be more effective in preventing lower respiratory tract involvement or other complications of influenza 10

than in preventing influenza infection. 11

Always check annual seasonal influenza vaccine availability statements on www.immunise.health.gov.au. 12

Vaccines and age eligibility change from year to year. 13

Vaccines for intramuscular administration* listed by age group 14

(see Table 4.7.1 for dosage information for different age groups) 15

Children aged ≥6 months to <3 years 16

FluQuadri Junior – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.25 mL pre-filled syringe 17

contains 7.5 µg haemagglutinin of each of the four recommended influenza virus strains; ≤50 µg formaldehyde; 18

≤125 µg octoxinol 9; ≤0.5 µg ovalbumin. 19

Influvac Junior – Abbott Products Pty Ltd (inactivated influenza virus). Each 0.25 mL pre-filled syringe 20

contains 7.5 µg haemagglutinin of each of the three recommended influenza virus strains. May contain traces of 21

formaldehyde, CTAB, polysorbate 80, gentamicin and egg protein. 22

Vaxigrip Junior – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.25 mL pre-filled syringe contains 23

7.5 µg haemagglutinin of each of the three recommended influenza virus strains. May contain traces of 24

formaldehyde, octoxinol 9, neomycin and egg protein. 25

Children aged ≥6 months† and adults 26

Agrippal – Novartis Vaccines and Diagnostics Pty Ltd (inactivated influenza virus). Each 0.5 mL pre-filled 27

syringe contains 15 µg haemagglutinin of each of the three recommended influenza virus strains. May contain 28

traces of kanamycin, neomycin, formaldehyde, barium sulphate, cetrimonium bromide (CTAB), polysorbate 80 29

and egg protein. 30

Fluarix – GlaxoSmithKline (inactivated influenza virus). Each 0.5 mL pre-filled syringe contains 15 µg 31

haemagglutinin of each of the three recommended influenza virus strains. May contain traces of formaldehyde, 32

gentamicin, polysorbate 80, octoxinol 10 and egg protein. 33

Influvac – Abbott Products Pty Ltd (inactivated influenza virus). Each 0.5 mL pre-filled syringe contains 15 µg 34

haemagglutinin of each of the three recommended influenza virus strains. May contain traces of formaldehyde, 35

CTAB, polysorbate 80, gentamicin and egg protein. 36

Vaxigrip – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.5 mL pre-filled syringe contains 15 µg 37

haemagglutinin of each of the three recommended influenza virus strains. May contain traces of formaldehyde, 38

octoxinol 9, neomycin and egg protein. 39

Children aged ≥3 years and adults 40

Fluarix Tetra – GlaxoSmithKline (inactivated influenza virus). Each 0.5 mL pre-filled syringe contains 15 µg 41

haemagglutinin of each of the four recommended influenza virus strains; polysorbate 80; octoxinol 10. May 42

contain traces of formaldehyde, gentamicin, hydrocortisone, sodium deoxycholate and egg protein. 43

FluQuadri – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.5 mL pre-filled syringe contains 15 µg 44

haemagglutinin of each of the four recommended influenza virus strains; ≤100 µg formaldehyde; ≤250 µg 45

octoxinol 9; ≤1 µg ovalbumin. 46

Children aged ≥9 years‡ and adults 47

4

Fluvax – CSL Limited (inactivated influenza virus).‡ Each 0.5 mL pre-filled syringe contains 15 µg 1

haemagglutinin of each of the three recommended influenza virus strains. May contain traces of neomycin, 2

polymyxin B, β-propiolactone, sodium taurodeoxycholate and egg protein. 3

Adults aged ≥65 years 4

Fluad – Novartis Vaccines and Diagnostics Pty Ltd (inactivated influenza virus). Each 0.5 mL pre-filled syringe 5

contains 15 µg haemagglutinin of each of the three recommended influenza virus strains, adjuvanted with 6

MF59C.1 (which contains squalene and polysorbate 80). May contain traces of kanamycin, neomycin, 7

formaldehyde, barium sulphate, CTAB and egg protein. 8

Vaccines for intradermal administration listed by age group 9

Adults aged 18–59 years 10

Intanza 9 μg – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.1 mL pre-filled purpose-designed 11

Micro-Injection System contains 9 µg haemagglutinin of each of the three recommended influenza virus strains. 12

May contain traces of formaldehyde, octoxinol 9, neomycin and egg protein. 13

Adults aged ≥60 years 14

Intanza 15 μg – Sanofi Pasteur Pty Ltd (inactivated influenza virus). Each 0.1 mL pre-filled purpose-designed 15

Micro-Injection System contains 15 µg haemagglutinin of each of the three recommended influenza virus 16

strains. May contain traces of formaldehyde, octoxinol 9, neomycin and egg protein. 17

* Influenza vaccines may also be administered via the SC route. However, the IM route is preferred (see 4.7.6 Dosage and administration below). 18

† Children aged 6 months to <3 years require a 0.25 mL dose (see 4.7.6 Dosage and administration and Table 4.7.1 Recommended doses of 19 influenza vaccine). 20

‡ Fluvax (CSL Limited) is registered by the Therapeutic Goods Administration (TGA) for administration in children ≥5 years of age; however, it is 21 not recommended for use in children <9 years of age (see 4.7.11 Adverse events and 4.7.13 Variations from product information below). 22

All the influenza vaccines currently available in Australia are either split virion or subunit vaccines prepared from 23

purified inactivated influenza virus that has been cultivated in embryonated hens’ eggs. The influenza virus composition 24

of vaccines for use in Australia is determined annually by the Australian Influenza Vaccine Committee and may differ 25

from that of northern hemisphere vaccine formulations.17

Influenza vaccines have traditionally contained three strains of 26

influenza virus – two influenza A subtypes and one influenza B lineage (i.e. trivalent influenza vaccines, or TIV). The 27

included strains represent the viruses predicted to circulate in the coming influenza season. Inactivated quadrivalent 28

influenza vaccines (QIV) containing four influenza virus strains (including an additional influenza B virus strain to 29

what is in the TIV) are now registered for use in Australia. Inactivated influenza vaccines (TIV and QIV) contain 15 µg 30

of viral haemagglutinin (or 9 µg in Intanza 9 µg) for each included virus strain. Vaccines specifically packaged for use 31

in children aged ≥6 months to <3 years contain 7.5 µg of viral haemagglutinin (in a 0.25 mL dose) of each of the same 32

influenza virus strains found in the adult formulations. 33

Split virion and subunit vaccines are generally considered to be equivalent with respect to safety, and both are 34

substantially free of the systemic reactions sometimes induced by whole virus vaccines. One exception is Fluvax (CSL 35

Limited), which in 2010 resulted in higher rates of adverse events, specifically fevers and febrile convulsions, in 36

children aged <5 years, in comparison with other influenza vaccines (see 4.7.11 Adverse events below).18

Because 37

influenza vaccine viruses are cultivated in embryonated hens’ eggs, these vaccines may contain traces of egg-derived 38

proteins. Manufacturing processes vary by manufacturer, and different chemicals (formaldehyde or β-propiolactone) 39

may be used to inactivate the virus. The product information for each vaccine should be consulted for specific 40

information. (See also ‘Vaccination of persons with a known egg allergy’ in 3.3.1 Vaccination of persons who have had 41

an adverse event following immunisation.) 42

Two intradermally administered influenza vaccines from the same manufacturer (Intanza 9 µg for use in adults aged 43

18–59 years and Intanza 15 µg for use in adults aged ≥60 years) have been registered in Australia since 2009. These 44

vaccines are presented in a purpose-designed syringe, the Micro-Injection System, which will deliver 0.1 mL of vaccine 45

to the dermis. These vaccines demonstrate comparable immunogenicity to influenza vaccines administered 46

intramuscularly and are likely to have similar efficacy. 47

Live attenuated intranasal influenza vaccine(s) are not currently registered in Australia and, worldwide, are not as 48

widely used as the currently available inactivated influenza vaccines.19,20

49

5

The efficacy and effectiveness of different split virion and subunit influenza vaccines are generally considered 1

equivalent. The majority of effectiveness studies have been done on TIV due to their widespread use. The efficacy and 2

effectiveness of influenza vaccine depends primarily on the age and immunocompetence of the vaccine recipient and 3

the degree of similarity between the virus strains in the vaccine and those circulating in the community.13,21-28

In 4

children, the burden of influenza is well documented, but there is less evidence for vaccine efficacy, particularly in 5

children aged <2 years.23

There have been few vaccine effectiveness studies undertaken in very young infants and 6

toddlers and these studies are difficult to compare due to differences in vaccine formulations and inclusion and 7

exclusion criteria, and the measurement of different clinical endpoints.29

A recent study has suggested that, during a 8

season with good vaccine match, vaccine effectiveness was between 60 and 85% in children ranging in age from 6 9

months to <6 years.29

When vaccine match was poor, vaccine effectiveness ranged from zero to about 60%.29

A recent 10

systematic review estimated the overall efficacy of inactivated vaccines against laboratory-confirmed influenza in 11

healthy adults <65 years of age to be 59%, although efficacy varied by influenza season.30

The efficacy of inactivated 12

influenza vaccine against influenza-like illness in persons ≥65 years of age living in the community is estimated to be 13

43% when viral circulation is high, although there have been few randomised controlled trials of influenza vaccine in 14

elderly people.31

A systematic review assessing vaccine effectiveness estimated that during periods of high virus 15

circulation, when vaccine match is good, influenza vaccination is approximately 45% effective against hospitalisations 16

due to influenza and pneumonia and 60% effective against all-cause mortality in persons aged >65 years in nursing 17

home settings.31

18

QIV are expected to be as effective as TIV. This is based on clinical studies in children and adults which demonstrated 19

QIV to be at least as immunogenic as TIV (an accepted surrogate for protection against influenza) for the three shared 20

influenza virus strains.32-35

QIV may offer additional benefit to TIV afforded by protection against the additional 21

influenza B lineage. However, the magnitude of this benefit would differ between influenza seasons as it depends on the 22

epidemiology of the additional influenza B lineage and any cross-protection against the additional B lineage gained 23

from that year’s TIV. 24

Currently available influenza vaccines confer protection for about a year. Low levels of protection may persist for a 25

further year, if the prevalent strain remains the same or undergoes only minor antigenic drift.13,28

Continuing protection 26

requires annual vaccination with vaccine containing the most recent strains. 27

4.7.5 Transport, storage and handling 28

Transport according to National vaccine storage guidelines: Strive for 5.36

Store at +2°C to +8°C. Do not freeze. Protect 29

from light. 30

At the end of each year, influenza vaccines should be appropriately discarded to avoid inadvertently using a product 31

with incorrect formulation in the following year. 32

4.7.6 Dosage and administration 33

Vaccines registered by the TGA, and the ages for which they are indicated, can change from year to year. Always check 34

annual seasonal influenza vaccine availability statements on www.immunise.health.gov.au, and consult individual 35

product information. 36

Influenza vaccines available in Australia for IM use are presented in pre-filled syringes, of either 0.5 mL or 0.25 mL. 37

The dose of vaccine to be administered varies by age, with children aged 6 months to <3 years requiring a 0.25 mL 38

dose. See Table 4.7.1 for the recommended doses of influenza vaccine for different age groups. Some 0.5 mL syringes 39

have a graduated mark to indicate where the plunger can be depressed to provide a 0.25 mL dose, if indicated. 40

Shake the pre-filled syringe vigorously before injection. Most influenza vaccines should be given by IM injection. 41

However, if administered by SC injection, the vaccine does not need to be re-administered. The IM route causes fewer 42

local reactions and is preferred over the SC route.37

43

Intradermal influenza vaccines are presented in a purpose-designed syringe containing 0.1 mL of vaccine, the Micro-44

Injection System, and do not require mixing before administration. They should be administered according to 45

manufacturer’s instructions. 46

Table 4.7.1: Recommended doses of influenza vaccine 47

Age Dose Number of doses

(first year of vaccination)

Number of doses*

(subsequent years)

6

6 months to <3 years 0.25 mL 2† 1

3 to <9 years 0.5 mL 2† 1

≥9 years 0.5 mL 1‡ 1

* If a child aged 6 months to <9 years receiving influenza vaccine for the first time inadvertently does not receive the 2nd dose within the same 1 year, he/she should have 2 doses administered the following year.38-40 2

† Two doses, at least 4 weeks apart, are recommended for children aged 6 months to <9 years who are receiving influenza vaccine for the first time. 3 The same vial should not be re-used for the 2 doses.36 4

‡ Two doses, at least 4 weeks apart, are recommended for persons with certain immunecompromising conditions who are ≥9 years of age and are 5 receiving influenza vaccine for the first time (see 3.3 Groups with special vaccination requirements). The same vial should not be re-used for the 6 2 doses. 7

Vaccination is best undertaken in autumn, in anticipation of winter outbreaks of influenza. However, vaccination can be 8

given as early as February if vaccine is available, particularly for the northern areas of Queensland and in the Northern 9

Territory where the seasonality of influenza differs from the southern states. In autumn, the opportunities to provide 10

influenza vaccination to persons at increased risk of influenza should not be missed during visits for routine medical 11

care. 12

As full protection is usually achieved within 10 to 14 days and there is evidence of increased immunity within a few 13

days, vaccination can still be offered to adults and children after influenza virus activity has been documented in the 14

community. 15

Co-administration with other vaccines 16

Influenza vaccine can be administered concurrently with other vaccines, including pneumococcal polysaccharide 17

vaccine and all scheduled childhood vaccines. However, parents/carers of infants or children who are recommended to 18

receive both influenza vaccine and 13-valent pneumococcal conjugate vaccine (13vPCV) should be advised of the small 19

increased risk of fever following concomitant administration of these vaccines (see 4.7.10 Precautions below and 4.13 20

Pneumococcal disease). 21

4.7.7 Recommendations 22

Annual influenza vaccination is recommended for any person ≥6 months of age for whom it is desired to reduce the 23

likelihood of becoming ill with influenza.5,6,41,42

24

Influenza vaccination is strongly recommended and should be actively promoted for the groups discussed below. 25

All adults aged ≥65 years 26

There is evidence that influenza vaccine reduces hospitalisations from influenza and pneumonia and all-cause mortality 27

in adults ≥65 years of age.31

(See also 4.7.4 Vaccines above.) 28

Persons at increased risk of complications from influenza infection 29

Persons aged ≥6 months with conditions predisposing to severe influenza,7 such as: 30

Pregnancy – Pregnant women (and women planning pregnancy) are recommended to be immunised against 31

influenza because they are at increased risk of morbidity and mortality from influenza and because there is good 32

evidence that influenza immunisation in pregnancy is safe and effective.43-50

The risk to the mother of 33

complications from influenza increases in the later stages of pregnancy.43-47,51-55

There is also a growing body of 34

evidence showing that influenza vaccination of pregnant women protects infants against influenza for the first 6 35

months after birth.44,56,57

Most evidence around infant protection is from studies of maternal influenza vaccination 36

in the second or third trimester.43-47,51-56

Influenza vaccination is thought to provide protection for up to a year, but 37

there is limited evidence that immunity may start to wane from 4 months following immunisation. Although it is 38

recommended that all pregnant women should be immunised as early as possible in pregnancy,58

the precise timing 39

of vaccination will depend on the time of the year, vaccine availability, influenza seasonality, gestation of 40

pregnancy and the likely duration of immunity. (See also 4.7.8 Pregnancy and breastfeeding below.) 41

Cardiac disease, including cyanotic congenital heart disease, coronary artery disease and congestive heart failure – 42

Influenza causes increased morbidity and mortality in children with congenital heart disease and adults with 43

coronary artery disease and congestive heart failure.42,59-62

44

7

Down syndrome – Persons with Down syndrome should receive annual seasonal influenza vaccine whether or not 1

they have congenital heart disease. This is due to the presence of anatomical abnormalities, which put them at 2

increased risk of upper respiratory tract infections, as well as a high prevalence of other medical conditions that put 3

them at increased risk of severe influenza.61

4

Obesity – Persons with a BMI ≥40 kg/m2 (classified as class

III obesity) should receive annual seasonal influenza 5

vaccine whether or not they have underlying comorbidities. Among individuals with a BMI ≥30, the greatest risk of 6

severe outcomes following A(H1N1)pdm09 strain influenza infection is in those with the greatest BMI.63-66

This 7

increased risk is independent of the presence of underlying comorbidities.67

There is some evidence that persons 8

who have a BMI between 30 and <40 (class II obesity) are also at increased risk of severe influenza outcomes and 9

may also benefit from annual influenza vaccine.63,67,68

10

Chronic respiratory conditions, including: 11

» Suppurative lung disease, bronchiectasis and cystic fibrosis42,60

– Patients with these diseases are at greatly 12

increased risk from influenza, which may cause irreversible deterioration in lung function.69

13

» Chronic obstructive pulmonary disease (COPD) and chronic emphysema42,70,71

– Data from several studies 14

provide evidence that influenza vaccination has a clinically important protective effect on influenza-related 15

COPD exacerbations, and probably an effect on the total number of exacerbations in COPD patients.70,71

16

» Severe asthma – In patients with severe asthma, defined as requiring frequent hospital visits and the use of 17

multiple medications, annual influenza vaccine is an important part of routine care.42,60

There are insufficient 18

data from randomised controlled trials of influenza vaccine to define efficacy across the whole spectrum of 19

asthma, but influenza can cause severe exacerbations of wheezing, and about 10% of episodes of virus-induced 20

wheezing are attributable to influenza. 21

Chronic neurological conditions (e.g. multiple sclerosis, spinal cord injuries, seizure disorders or other 22

neuromuscular disorders) – These conditions can compromise respiratory function or the expulsion of respiratory 23

secretions that can then increase the risk for aspiration.42,60

Influenza vaccination is particularly important for 24

children ≥6 months of age with chronic neurological conditions as these children can experience severe, even fatal, 25

influenza. 26

Immunocompromising conditions – Persons who are immunocompromised, including those with HIV infection, 27

malignancy or chronic steroid use, are at an increased risk from influenza (see 3.3.3 Vaccination of 28

immunocompromised persons).42,60

They may also have a reduced immune response to the vaccine, although 29

influenza vaccination affords some protection.72

Influenza vaccination is recommended annually in all 30

immunocompromised patients aged ≥6 months. 31

Persons with certain immunocompromising conditions (e.g. haematopoietic stem cell transplant, solid organ 32

transplant), who receive influenza vaccine for the first time, are recommended to receive 2 vaccine doses at least 4 33

weeks apart (irrespective of age) and 1 dose annually thereafter (see 3.3.3 Vaccination of immunocompromised 34

persons). Where it is known that a new influenza vaccine strain is circulating in the community to which cross-35

protective immunity in the population is low (such as in the setting of an influenza pandemic), it may be 36

appropriate that immunocompromised persons receive 2 doses of inactivated influenza vaccine, a minimum of 4 37

weeks apart, to achieve an optimal immune response, irrespective of their previous influenza vaccination history. 38

For example, in the 2009–2010 H1N1 global influenza pandemic it was shown that seroconversion to influenza 39

vaccination in immunocompromised adolescents and adults was improved following receipt of 2 vaccine doses.73

40

Further information and annual influenza vaccine recommendations are available on the Immunise Australia 41

website (www.immunise.health.gov.au). 42

While patients with advanced HIV disease and low CD4+ T-lymphocyte counts may not develop protective 43

antibody titres, there is evidence that for those with minimal symptoms and high CD4+ T-lymphocyte counts, 44

protective antibody titres are obtained after influenza vaccination. Influenza vaccine has been shown to reduce the 45

incidence of influenza in HIV-infected patients, and, although viral load may increase transiently, there was no 46

impact on CD4+ count.

72 (See also 3.3 Groups with special vaccination requirements, Table 3.3.4.) 47

Chronic liver disease – persons with histological evidence of fibrosis or cirrhosis and/or clinical evidence of 48

chronic liver disease due to various causes, including alcoholism, are at increased risk of severe outcomes 49

following influenza infection.63,74,75

50

Other chronic illnesses requiring regular medical follow-up or hospitalisation in the preceding year, including: 51

» diabetes mellitus42,60,76

52

8

» chronic renal failure42,60

1

» [note: text deleted] 2

» haemoglobinopathies60

3

» chronic inherited metabolic diseases (which includes amino acid disorders, carbohydrate disorders, cholesterol 4

biosynthesis disorders, fatty acid oxidation defects, lactic acidosis, mitochondrial disorders, organic acid 5

disorders, urea cycle disorders, vitamin/cofactor disorders, porphyrias)42,60

6

Long-term aspirin therapy in children (aged 6 months to 10 years) – Such children are at increased risk of Reye 7

syndrome after influenza.77,78

8

Aboriginal and Torres Strait Islander people 9

Annual influenza vaccination is strongly recommended for all Aboriginal and Torres Strait Islander people 6 months to 10

<5 years and ≥15 years of age in view of their substantially increased risk of severe outcomes following influenza.79

11

(See also 3.1 Vaccination for Aboriginal and Torres Strait Islander people.) Aboriginal and Torres Strait Islander 12

children aged 5 to 14 years are at lower risk of severe influenza than other ages.79

However, annual influenza 13

vaccination of children in this age group can still offer individual protection against influenza as well as indirect 14

protection to their household members who are at increased risk of severe influenza (see Persons who may transmit 15

influenza to persons at increased risk of complications from influenza infection). 16

Children aged <5 years 17

Infants and children aged <5 years are at increased risk for hospitalisation and increased morbidity and mortality 18

following influenza (see Figure 4.7.1).9 This includes young children without pre-existing medical conditions, who have 19

been found to be at increased risk for hospitalisation compared with older children and adults.80-82

Specific brands are 20

registered by the TGA for use in children ≥6 months of age and these may change from year to year (see 4.7.6 Dosage 21

and administration above). 22

Residents of residential aged care facilities and long-term residential facilities 23

Annual influenza vaccination is recommended for residents of these facilities, including inmates of correctional 24

facilities, due to high rates of influenza transmission and complications during outbreaks in such facilities.12,13,71

25

Homeless people 26

The living conditions and prevalence of underlying medical conditions among homeless people will predispose them to 27

complications and transmission of influenza. 28

Persons who may transmit influenza to persons at increased risk of complications from influenza 29

infection 30

The following groups of people can potentially transmit influenza to persons at increased risk of complications from 31

influenza infection; vaccination of these groups is therefore recommended to protect those at risk: 32

all healthcare providers (particularly those of immunocompromised patients) 33

staff (or volunteers) working in nursing homes 34

staff (or volunteers) working in long-term care facilities 35

household contacts (including children ≥6 months of age) of those in high-risk groups, including providers of home 36

care to persons at risk of high influenza morbidity 37

staff working in early childhood education and care 38

staff (or volunteers) providing care to homeless people. 39

Persons involved in the commercial poultry or pork industry or in culling poultry or pigs during 40

confirmed avian or swine influenza activity 41

Vaccination using the seasonal influenza vaccine composition current at the time is recommended for poultry or piggery 42

workers and others in regular close contact with poultry or pigs during an avian or swine influenza outbreak.83

Although 43

routine seasonal influenza vaccine does not protect against avian or swine influenza, there is a possibility that a person 44

who is infected at the same time with animal and human strains of influenza virus could act as a vessel for reassortment 45

of the two strains to form a virulent strain, with the potential for spread from human to human (i.e. initiate a pandemic 46

9

as was the case with swine influenza in 2009).84

In addition, vaccination can also prevent the transmission of influenza 1

from humans to animals. 2

Persons providing essential services 3

Vaccination of those who provide essential community services will minimise disruption of essential activities during 4

influenza outbreaks. Influenza viral infections can place considerable pressure upon both public and private healthcare 5

services (see 3.3 Groups with special vaccination requirements, Table 3.3.7 Recommended vaccinations for persons at 6

increased risk of certain occupationally acquired vaccine-preventable diseases). 7

Workers in other industries 8

Due to the high attack rate of influenza in the general population, influenza vaccination in the workplace can result in 9

benefits such as increased productivity and reduced absenteeism among workers.85

Employers should consider the 10

benefits of offering influenza vaccine in their individual workplace. 11

Travellers 12

Influenza vaccine is particularly relevant if influenza epidemics are occurring at the traveller’s destination(s). Travellers 13

in large tourist groups, especially those including older people, those travelling on cruises, and/or those who are likely 14

to be in confined circumstances for days to weeks, are at risk of influenza, either acquired before departure or from 15

travel to areas of the world where influenza is currently circulating. Influenza vaccination is recommended if travelling 16

during the influenza season, especially if it is known before travel that influenza is circulating in the destination 17

region.86

(See also 3.2 Vaccination for international travel.) 18

4.7.8 Pregnancy and breastfeeding 19

Influenza vaccination is recommended for pregnant women (see 4.7.7 Recommendations above) and is safe to 20

administer during any stage of pregnancy or while breastfeeding.49,87-89

21

Refer to 3.3 Groups with special vaccination requirements, Table 3.3.1 Recommendations for vaccination in pregnancy 22

for more information. 23

4.7.9 Contraindications 24

The only absolute contraindications to influenza vaccines are: 25

anaphylaxis following a previous dose of any influenza vaccine 26

anaphylaxis following any vaccine component. 27

See 4.7.10 Precautions below for persons with a known egg allergy. 28

4.7.10 Precautions 29

Persons with known egg allergy90-94

30

Several recently published reviews, guidelines and reports have indicated that the risk of anaphylaxis associated with 31

influenza vaccination of egg-allergic patients is very low.90-94

Persons with egg allergy, including anaphylaxis, can be 32

safely vaccinated with influenza vaccines that have less than 1 μg of residual egg ovalbumin per dose.90,92

Due to 33

changes in influenza vaccine manufacturing, the majority of influenza vaccines currently used contain less than 1 μg of 34

ovalbumin per dose.90

Note the amount of residual egg ovalbumin may vary from year to year due to manufacturing 35

processes, batches and country of origin.90,92,93

The product information (PI) of the vaccine to be given should be 36

checked for the vaccine’s ovalbumin content prior to vaccine administration. Allergy testing with influenza vaccine 37

prior to administration is not recommended as there is poor correlation between test results and vaccine tolerance.90,92-94

38

However, there is still a low risk of anaphylaxis, so it is essential that such patients are vaccinated in facilities with staff 39

able to recognise and treat anaphylaxis. Additional information on influenza vaccination of individuals with an allergy 40

to eggs, including risk, dosage and observation period, can be found in the Australasian Society of Clinical Immunology 41

and Allergy (ASCIA) guidelines.92

(See also ‘Vaccination of persons with a known egg allergy’ in 3.3.1 Vaccination of 42

persons who have had an adverse event following immunisation.) 43

Persons with a history of Guillain-Barré syndrome 44

Persons with a history of Guillain-Barré syndrome (GBS) have an increased likelihood in general of developing GBS 45

again, and the chance of them coincidentally developing the syndrome following influenza vaccination may be higher 46

10

than in persons with no history of GBS.95

Diagnosis of GBS is complex and must be made by a physician. (See also 1

4.7.11 Adverse events below.) 2

Children requiring both influenza and 13-valent pneumococcal conjugate vaccine 3

There is a slightly higher risk of fever and febrile convulsions in children aged 6 months to <5 years (especially those 4

aged 12 to 24 months) with the concurrent administration of 13vPCV and inactivated trivalent influenza vaccine 5

(compared with giving the vaccines separately).96

(See also 4.13 Pneumococcal disease.) The risk was estimated to be 6

about 18 excess cases per 100 000 doses in children aged 6 to 59 months, with a peak of 45 per 100 000 doses in those 7

aged 16 months. Given the reported increase in risk is relatively small, providing 13vPCV and inactivated trivalent 8

influenza vaccine concurrently is acceptable; however, immunisation service providers should advise parents of the risk 9

and provide the option of administering these two vaccines on separate days (with an interval of not less than 3 days). 10

4.7.11 Adverse events 11

Fever, malaise and myalgia occur commonly, in 1 to 10% of persons who receive inactivated influenza vaccination.97-99

12

These adverse events may commence within a few hours of vaccination and may last for 1 to 2 days.97-99

In children 13

<5 years of age, these side effects may be more pronounced. In 2010, an excess of fever and febrile convulsions 14

following influenza vaccination was reported in children aged <5 years, particularly children aged <3 years. This was 15

associated only with one manufacturer’s vaccine (Fluvax and Fluvax Junior, CSL Limited); following vaccination with 16

this vaccine, febrile convulsions occurred at a rate of 4.4 per 1000 doses in children <5 years of age.100

This vaccine is 17

no longer registered for use in children aged <5 years and is not recommended for administration in children aged <9 18

years (see 4.7.4 Vaccines above). 19

Local adverse events (induration, swelling, redness and pain) occur in more than 10% of vaccine recipients, following 20

IM influenza vaccine administration.98,99

Local adverse events (induration, redness, swelling and pruritus) occur more 21

commonly following intradermal influenza vaccine administration. However, most patients report that these events are 22

transient and resolve fully within a few days.101

23

Studies directly comparing trivalent and quadrivalent inactivated influenza vaccine formulations in children and adults 24

have demonstrated a similar safety profile.32-35

25

Post-vaccination symptoms may mimic influenza infection, but all currently available influenza vaccines do not contain 26

live virus and so do not cause influenza. 27

Immediate adverse events (such as hives, angioedema or anaphylaxis) are a rare consequence of influenza vaccination. 28

They probably represent an allergic response to a residual component of the manufacturing process, most likely egg 29

protein.90,92

Persons with a history of anaphylaxis after eating eggs or a history of a severe allergic reaction following 30

occupational exposure to egg protein may receive influenza vaccination after medical consultation.90,92

31

A small increased risk of GBS was associated historically with one influenza vaccine in the United States in 1976, but, 32

since then, close surveillance has shown that GBS has occurred at a very low rate of up to 1 in 1 million doses of 33

influenza vaccine, if at all.102

Diagnosis of GBS is complex and must be made by a physician (see ‘Uncommon/rare 34

AEFI’ in 2.3.2 Adverse events following immunisation). 35

Narcolepsy (sudden sleeping illness) has been described predominantly in the Scandinavian population, in association 36

with adjuvanted pandemic influenza vaccines.103,104

These vaccines were not used and are not available in Australia. 37

4.7.12 Public health management of influenza 38

Laboratory-confirmed cases of influenza are notifiable in all states and territories in Australia. Detailed information 39

regarding the management of influenza cases and contacts can be found in the national guidelines for control of 40

influenza105

(www.health.gov.au/cdnasongs). 41

Further instructions about the public health management of influenza can also be obtained from state/territory public 42

health authorities (see Appendix 1 Contact details for Australian, state and territory government health authorities and 43

communicable disease control). 44

4.7.13 Variations from product information 45

The product information for influenza vaccines lists allergy to eggs, chicken feathers and/or some food proteins as a 46

contraindication. The ATAGI recommends instead that patients with egg allergies and other allergies can be vaccinated 47

under strict medical supervision, in accordance with ASCIA guidelines.92

48

11

The product information for Fluvax (CSL Limited) states that this vaccine is registered for use in children ≥5 years of 1

age. However, the ATAGI does not recommend the use of this vaccine in children aged <9 years. 2

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RELEVANT TEXT FROM OTHER CHAPTERS OF THE AUSTRALIAN IMMUNISATION 1

HANDBOOK 10TH EDITION 2

UPDATED TO ALIGN WITH CHANGED RECOMMENDATIONS IN CHAPTER 4.7 3

INFLUENZA 4

5

3.1 VACCINATION FOR ABORIGINAL AND TORRES STRAIT ISLANDER PEOPLE 6

3.1.1 Children 7

Influenza 8

Annual influenza vaccination is strongly recommended for all Aboriginal and Torres Strait Islander people 6 months to 9

<5 years and ≥15 years of age in view of their substantially increased risk of severe outcomes following influenza (see 10

also ‘Influenza’ in 3.1.2 Adults below). Aboriginal and Torres Strait Islander children aged 5 to 14 years are at lower 11

risk of severe influenza than other ages. However, annual influenza vaccination of children in this age group can still 12

offer individual protection against influenza as well as indirect protection to their household members who are at 13

increased risk of severe influenza (see 4.7 Influenza). 14

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