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7/30/2019 Timing of Measles Immunizatioon and Effective Population Vaccine Coverage - Magda Delicia
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DOI: 10.1542/peds.2012-0132; originally published online August 20, 2012;2012;130;e600Pediatrics
Julia A. Bielicki, Rita Achermann and Christoph BergerTiming of Measles Immunization and Effective Population Vaccine Coverage
http://pediatrics.aappublications.org/content/130/3/e600.full.html
located on the World Wide Web at:The online version of this article, along with updated information and services, is
of Pediatrics. All rights reserved. Print ISSN: 0031-4005. Online ISSN: 1098-4275.Boulevard, Elk Grove Village, Illinois, 60007. Copyright 2012 by the American Academypublished, and trademarked by the American Academy of Pediatrics, 141 Northwest Point
publication, it has been published continuously since 1948. PEDIATRICS is owned,PEDIATRICS is the official journal of the American Academy of Pediatrics. A monthly
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Timing of Measles Immunization and Effective
Population Vaccine Coverage
WHATS KNOWN ON THIS SUBJECT: Many children are vaccinatedagainst measles with a delay. This may influence effective measles
vaccine coverage even in countries with high overall
immunization levels. Official vaccine coverage statistics do not
usually report on the impact of timeliness of measles vaccination.
WHAT THIS STUDY ADDS: Delayed measles vaccination results in
48.6% effective coverage in children aged 6 months to 2 years
when 84.5% of 25-month-olds are up-to-date for 1 measles
vaccination. Analyzing patterns of measles vaccination could help
to address low coverage in infants and toddlers.
abstractOBJECTIVE: To describe measles vaccination patterns in a cohort
of Swiss children aged up to 3 years insured with a single health
insurer.
METHODS: A dynamic cohort study evaluating measles immunizations
patterns in children born between 2006 and 2008 was conducted. Time-
to-event analysis was used to describe timing of measles immunization.
Effective vaccine coverage was calculated by using an area under the
curve approach.RESULTS: In the study cohort, 62.6% of 13-month-old children were up-to-
date for the first measles immunization (recommended at 12 months of
age). Approximately 59% of 25-month-old children were up-to-date for
the second measles immunization (recommended at 1524 months of
age). Most doses were delivered during months in a child s life when
well-child visits are recommended (eg, 12 months of age). For second
measles vaccine dose, accelerations in vaccine delivery occurred at
time points for well-child visits during the months 19 and 25 of age
but with lower final uptake than for the first measles vaccine dose.
Until their second birthday, children in our cohort spent on average 177
days and 89 days susceptible to measles due to policy recommendationsand additional delays, respectively. In a group of children aged 6 months
to 2 years reflecting the age distribution in our cohort, effective vaccine
coverage was only 48.6%.
CONCLUSIONS: Timing and timeliness of measles immunizations influ-
ence effective population vaccine coverage and should be routinely
reported in addition to coverage whenever possible. Proposed timing
and relation of recommended vaccinations to well-child visits could be
relevant aspects in optimizing measles vaccine coverage to reach
measles elimination. Pediatrics 2012;130:e600e606
AUTHORS:Julia A. Bielicki, MD, MPH,
a,b
Rita Achermann,MSc,c,d and Christoph Berger, MDa,b
aDivision of Infectious Diseases and Hospital Epidemiology, andbChildrens Research Centre, University Childrens Hospital,
Zurich, Switzerland; cHelsana Health Insurance Company,
Duebendorf, Switzerland; and dInstitute for Clinical Epidemiology
and Biostatistics, University Hospital Basel, Basel, Switzerland
KEY WORDS
immunization programs, immunization schedule, measles, time
factors, vaccination
ABBREVIATIONS
CIconfidence interval
FOPHSwiss Federal Office of Public Health
MCV1first measles vaccine dose
MCV2second measles vaccine dose
Drs Bielicki and Berger designed the study and, shaped the data
analysis with assistance from Ms Achermann. Ms Achermann
obtained anonymized data from the Helsana Health Insurance
Company database and conducted the data analysis. All authors
contributed to the interpretation of the results. Dr Bielicki
drafted and revised the manuscript. Dr Berger and Ms
Achermann commented on the initial draft and revisions and
approved the final version.
The findings and conclusions in this report are those of the
authors and do not necessarily represent the official position of
Helsana Health Insurance Company.
www.pediatrics.org/cgi/doi/10.1542/peds.2012-0132
doi:10.1542/peds.2012-0132
Accepted for publication May 10, 2012
Address correspondence to Christoph Berger, MD, Division of
Hospital Epidemiology and Infectious Disease, University
Childrens Hospital, Steinwiesstrasse 75, 8032 Zurich, Switzerland.
E-mail: [email protected]
PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275).
Copyright 2012 by the American Academy of Pediatrics
FINANCIAL DISCLOSURE: Ms Achermann was head of the
division of health sciences at Helsana Health Insurance
Company when this study was conceived. There were no
financial incentives provided by the company for work on this
article. Ms Achermann has since moved to the Centre for
Biostatistics and Clinical Epidemiology at the University of Basel.
Permission was granted to complete this article after her
employment with Helsana Health Insurance Company
terminated. The other authors have indicated they have no
financial relationships relevant to this article to disclose.
FUNDING: No external funding.
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Vaccination is a key and highly suc-
cessful element of well-child care
worldwide. Over the last few decades,
effective vaccines and immunization
programshave dramatically reducedthe
impact of several vaccine-preventable
diseases on population and individualhealth.1 Adequate population coverage
to achieve high individual protection as
well as for induction and maintenance
of herd immunity is an important issue
in the fight against many vaccine-
preventable diseases.2
Despite being vaccine preventable,
measles is still a relevant disease that
continues to be a major focus for im-
munization programs.3 Available mea-
sles vaccines are highly efficacious andare an adequate instrument to elimi-
nate endemic measles transmission if
coverage is maintained at .95%, the
level necessary to achieve herd immu-
nity.2,4 After intense vaccination efforts,
interruption of endemic transmission of
measles has been achieved in Finland
and Iceland, as well as American
countries, showing that measles vac-
cines can be effective in a population
setting.
5,6
Immunization programs withcarefully chosen evidence-based rec-
ommended times for vaccination are
key to ensure that elimination of mea-
sles can be achieved.7 In addition, such
programs must be well accepted by
the target populations.8 In Switzerland,
measles vaccination coverage much
below the desirable 95% coverage has
been recorded repeatedly.9,10 Moreover,
significant delays to measles immuni-
zation have been described for 1 region
of Switzerland.11 A similar picture pres-
ents itself in many European countries,with reported vaccination coverage
#84% in 2009 for, among others, Aus-
tria, Belgium, and the United Kingdom.12
Appropriate and valid information on
vaccine coverage is crucial to main-
taining, supplementing, and expanding
measles immunization programs.7
The aims of the current study were to
assess measles immunizationlevels and
patterns in a Swiss cohort of children
bornbetween2006and2008andinsuredwith a single health insurer. Specific
objectives were to evaluate the value of
incorporating timeliness and timing of
firstand seconddose of measles vaccine
administration in describing vaccine
coverage for the study population.
METHODS
Setting
Health care in Switzerland is providedwithin a system of compulsory health
insurance administrated through a
number of federally recognized insur-
ance funds (see Supplemental Informa-
tion).13 Health insurance is divided into
basic mandatory insurance and voluntary
top-up plans covering a limited range of
additionalservices.At least 90%of costs
of vaccinations and well-child visits are
covered by basic insurance with a max-
imum annual copayment of 350 Swiss
francs. Vaccinations in Switzerland are
overwhelmingly administered by physi-cians in an office-based setting. Invoices
for outpatient care are standardized,
and vaccines can be identified by codes
or text from submitted bills.
In the Swiss national vaccination
schedule, thefirst measles vaccine dose
(MCV1) is recommended at 12 months
of age, with earlier immunization at 6 or
9 months of age advised for children
considered at high risk of exposure to
measles. For example, early measlesvaccinationfrom9monthsofagemaybe
considered for children attending day
care. The second dose (MCV2) is gen-
erally recommended at 15 to 24 months
of age. Infantswho were immunizedwith
MCV1 aged,12 months should be given
MCV2 at 12 months of age.14 Seven well-
child visits are recommended between
2 and 24 months of age (Fig 1).15
Study Design
A dynamic cohort study was conducted
retrospectively looking at claims data
from Helsana Health Insurance Com-
pany (hereafter referred to as Helsana)
inSwitzerland.Allchildrenbornbetween
January 1, 2006, and June 30, 2008,
FIGURE 1Recommendedvaccinationschedule andwell-childvisitsfor children upto 2 years of agein Switzerlandin 2011.19,20DTaP IPV +Hib,diphtheria-tetanus-acellular
pertussis vaccine, inactivated poliovirus vaccine, Haemophilus influenzaetype b conjugate vaccine; Men C, meningococcal serogroup C conjugate vaccine;
MMR, measles-mumps-rubella vaccine; PCV13, 13-valent pneumococcal conjugate vaccine.
ARTICLE
PEDIATRICS Volume 130, Number 3, September 2012 e601at Indonesia:AAP Sponsored on September 6, 2012pediatrics.aappublications.orgDownloaded from
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insured from no later than 4 weeks of
age with Helsana were included. Chil-
dren with unknown places of residence
or notresidentin Switzerland at thetime
of birth were excluded.
The date of vaccination for each child in
the cohort was assumed to coincidewith the dispensing date specified on
the submittedinvoice. Each individualin
the cohort was continuously observed
from registration until the end of the
observation period on June 30, 2010.
Censoring of observation occurred at
the following events: death of the child,
change of health insurance, or erro-
neous billing for vaccines (eg, identical
invoices with treatment dates ,10
days apart).During the observation period, vacci-
nations against measles alone (Mea-
sles Vaccine [live], Pro VaccineAG, Baar,
Switzerland)orincombinationwith mumps
and rubella (Priorix, GlaxoSmithKline AG,
Mnchenbuchsee, Switzerland; M-M-
RVaxPro, Sanofi Pasteur MSD AG, Baar,
Switzerland) delivered in an ambulatory
setting were recorded as significant
events.
Data Analysis
Statistical analyses were conducted by
using R version 2.12.2 (R Foundation for
Statistical Computing, Vienna, Austria).
Health insurance data have previously
been shown to provide valid estimates
of vaccine coverage.16 Data from the
claims database were used to calcu-
late vaccination coverage by using a
time-to-event analysis.17 The age at
vaccination in days was calculatedfrom date of birth to the visit date on
submitted invoices. Inverse Kaplan-Meier
curves were plotted to display cumu-
lative measles vaccine coverage. Pro-
portion of children vaccinated with
MCV1 and MCV2 was considered at
13 and 25 months of age to reflect
immunization levels at the recom-
mended ages for measles vaccination
in Switzerland.14 Up-to-date vaccination
was defined as occurring within 30 days
of the recommended age.18 Ninety-five
percent confidence intervals (95% CIs)
were calculated by using the Greenwood
formula. All data presented are adjusted
for market share of the health insurance
on the level of canton and gender.19
To assess the validity of calculated
measles vaccination levels in our co-
hort, we compared our data against
official nationwide estimates for 24- to
35-month-old children published by the
Federal Office of Public Health (FOPH)
for 20052007.9 Official vaccine cover-
age estimates are based on data from
postal surveys with review of vaccina-
tion cards for 24- to 35-month-olds.9
The response rate to these surveys is85%. Nonrespondents are known to
be more likely German-speaking, non-
Swiss, and urban, but the exact effect
of these findings cannot be quantified.
The average measles vaccine coverage
in the same age range was calculated
from our data by using an area under
the curve approach.20 95% CIs were
calculated for these proportions with
bootstrapping (80% sample with re-
placement).The same area under thecurve approach was used to estimate
effective vaccine coverage for children
up to the age of 2 to 3 years, taking into
account any delays in immunization.20
All information in thedatabasewas fully
anonymized in accordance with Swiss
data protection laws.
RESULTS
Description of Study Cohort andAdministered Vaccine Doses
A total of 42 950 infants (52% males)
born between January 1, 2006, and
June 30, 2008, were included in the
cohort. The cohort represents just
,20% of children born in Switzerland
during the same period (19.6% for
males, 19.1% for females). The average
observation period for successive an-
nual birth cohorts was 978 days, 868
days, and 601 days for infants born in
2006, 2007, and 2008, respectively.
During the observation period, 45 605
measles-containing vaccine doses were
administered to children in our cohort.
For MCV1 and MCV2, a combination
vaccine of measles, mumps, and rubellawas used in 99.3% and 99.5% of cases,
respectively. The remaining immuniza-
tions consisted of a stand-alone mea-
sles vaccine.
There were a total of 145 invalid mea-
sles vaccinations either because of
immunization before therecommended
minimum age (before 6 months of age
for MCV1 and before 12 months of age
for MCV2, respectively; n=92)ordueto
an insufficient time interval betweenvaccinations (,4 weeks, n= 53). These
constituted 0.003% (145 of 45 605) of all
observed measles vaccinations and
were ignored for subsequent analyses.
Proportion of Children Up-to-Date
for MCV1 and MCV2
Only 62.6% (95% CI: 62.362.8) of
13-month-old children in our cohort had
received MCV1 and were up-to-date with
respect to the recommended schedule.Still, only 84.5% (95% CI: 84.384.7) of
25-month-old children had been given
MCV1. An even larger discrepancy was
noted for MCV2, with only 59.4% of
children immunized at 25 months of age
(95% CI: 59.159.6).
Measles immunization levels in the study
cohort were compared with survey-
based estimates produced by the FOPH
for the period 20052007.9 Our results
for average proportions of childrenimmunized with MCV1 and MCV2 by age
24 to 35 months broadly corresponded
to officially reported immunization lev-
els (Table 1). A basic sensitivity analysis
to explore various proportions of MCV
coverage for the nonrespondents in the
FOPH survey found that the current
data were compatible with official esti-
mates unless all nonrespondents are
unvaccinated (Table 2).
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Timeliness and Timing of Measles
Vaccination
In addition to considering measles vac-
cination statusby looking at proportion
of children up-to-date at specified time
points, theeffectof timeliness andtiming
on vaccination coverage was explored
(Fig 2).
Of the MCV1 doses in our cohort, about
one-half were administered within anarrow time band between 365 (19.6%
immunized) and 395 days (62.6% im-
munized) of age, corresponding to the
recommended age for MCV1 adminis-
tration. Another 21.9% of children re-
ceived MCV1 thereafter up to the age
of 25 months. Almost 20% of MCV1
immunizations occurred before the
generally recommended age of 12
months (2.7% immunized at 9 months,
19.4%immunized at 11 monthsof age),
probably reflecting vaccine uptake be-
fore daycare attendance.Themajorityof
MCV2 doses also were administered
during the recommended interval (6.6%
immunized at 15 months, 59.4% at 25
months). However, delivery occurred
more spread out over time, with the rate
of MCV2 vaccination accelerating at 15
monthsbut even more so during months
19 and 25 of age at times of recom-
mended well-child visits. MCV2 admin-
istration continued to occur after 25
months of age, reaching 71.2% (95% CI:
71.071.5) for 36-month-olds.
Cohort Effect of DelayedVaccination on Vulnerability to
Measles
For calculations of effective population
coverage, we assumed waning of ma-
ternal antibodiesat 6 months of age and
92.5% and 94% vaccine effectiveness
for MCV1 and MCV2, respectively.4,21
Therefore, children were taken to be
susceptible to measles from 6 months
before the recommended age for
MCV1. Taking into account the timingand timeliness of measles immuniza-
tion, children in our cohort spent on
average 266 days (95% CI: 265.1266.8)
unvaccinated and susceptible to mea-
sles until their second birthday. Of the
susceptible days, 66.5% were spent
susceptible due to the policy of rec-
ommending MCV1 for 12-month-olds
and despite early uptake of MCV1 be-
tween 9 and 12 months by 20%
in our cohort. Conversely, 33.5% of
susceptible days were due to delayed
vaccinations.
To investigate the impact of vaccination
timing and timeliness on effective cov-
erage among young children, we cal-
culated the proportion of susceptiblechildren for a hypothetic group of in-
fants and toddlers aged 6 months to
2 years. The chosen age range is rep-
resentative of a substantial propor-
tion of c hildren in day care groups in
Switzerland and elsewhere, an envi-
ronment where measles transmissions
could easily occur during an outbreak.
The relative age distribution and mea-
sles vaccination levels in this group
reflected that in our cohort. In sucha group and under the same assump-
tions as detailed previously, on average
48.6% of children are susceptible to
measles at current levels of vaccina-
tion. The recommended timing of MCV1
and the resulting 6 months that chil-
dren may spend susceptible to mea-
sles even when up-to-date with respect
to the immunization schedule had the
largest impact on effective coverage.
Inclusion of older children in this hy-pothetical group shows the additional
effects of timeliness. Among children
aged 6 months to 3 years, effective
vaccine coverage would be 61.3%, the
higher coverage largely reflecting on-
going immunization activity after the
recommended ages for MCV1 and MCV2
vaccination.
DISCUSSION
By using health insurance data for acohort of.40 000 Swiss children born
between 2006 and 2008, we were able
to demonstrate that 62.6% and 59.4% of
our cohort were up-to-date for MCV1
and MCV2 at 13 and 25 months of age,
respectively. Average coverage at 24
to 35 months of age was found to be
broadly in the range of official esti-
mates, with 85.7% and 66.7% for MCV1
and MCV2.
TABLE 1 Vaccine Coverage for 24- to 36-Month-Olds Comparing Data for the Study Cohort InsuredWith a Single Health Insurer Between 2006 and 2010 Versus Official Nationwide Postal
Survey-Derived FOPH Data for 2005 to 2007a
Data Source Age Vaccine Coverage, % (95% CI)
MCV1 MCV2
Helsana 13 mob 62.6 (62.362.8)
25 mob 84.5 (84.384.7) 59.4 (59.159.6)
2435 moc 85.7 (85.386.2) 66.7 (66.167.2)
FOPHc 2435 mo 86.9 (NA) 70.8 (NA)
NA, not available.a Data from Lang et al.9
b Cumulative proportion vaccinated at indicated age.c Calculated average proportion vaccinated in indicated age range.
TABLE 2 Calculating Range of PossibleMeasles Vaccine Coverage for
Comparison of Official Nationwide
Survey Data With the Helsana
Cohort: Sensitivity Analysis
Assuming Different Vaccination
Status Among NonrespondentsWith Official Nationwide Surveya
Assumed Vaccination
Status of
Nonrespondentsb
Calculated Vaccine
Coverage, %
MCV1 MCV2
All vaccinated 89.9 76.4
Coverage of
respondents =
nonrespondents
87.5 71.5
All unvaccinated 73.7 60.1
a Data from Lang et al.9
b Total FOPHsurveysamplesize = 9787; respondents = 8286
(84.7%).
ARTICLE
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By conducting a time-to-event analysis,
we were able to consider the additional
impact of timeliness and timing of ad-
ministration of measles vaccine on ef-
fective vaccine coverage. In a group ofchildren aged 6 months to 3 years,
40% of children were susceptible to
measles despite a vaccination level of
71.2% for MCV2 at 36 months in our
cohort, clearly demonstrating the
combined impact of policy consid-
erations (time point for recommended
MCV1 and MCV2) and individual delayed
immunization on overall population
coverage.
Our data confirm previous observa-tions that when describing immuni-
zation levels in a given population, the
choice of reported parameters influ-
ences the interpretation of vaccine
coverage.18,20,2225 Where vaccination
achieves much of its population effect
through herd immunity, simply consid-
ering immunization levels at a given
age may overestimate protection in the
population of interest.20,22,24 The effect of
individual delayed childhood vaccina-
tions on the fraction vaccinated in
whole populations was shown to effect
whether critical population immunity
levels could be achieved.24 Time-to-eventanalysis results in a more compre-
hensive representation of population
vaccination levels than proportions of
individuals up-to-date at key ages alone.
Timing is relevant in that spread-out
vaccine delivery can result in relevant
reductionsineffectivevaccinecoverage
even when overall final uptake of vac-
cinations is similar.25 In our cohort,
most vaccinations took place during
the time periods recommended in thenational schedule. This in itself gave
rise to a considerable number of days
spent susceptible when waning im-
munity from maternal antibodies was
assumed to occur at 6 months of age.21
Thus, around two-thirds of, on average,
266 days spent unvaccinated and sus-
ceptible to measles until 2 years of age
were due to a gap between policy rec-
ommendations and waning immunity
with the remainder being down to
delay ed immunizations in the cohort.
For MCV1, timing of recommended vac-
cination seemed to be the key driver for
when children were vaccinated. Con-versely, administration of MCV2 was
drawn out during the recommended
time period of 15 to 24 months, reflect-
ing poor timeliness of vaccination.
Greater delays for later vaccinations
in young children have been noted in
other settings.26,27
At current effective coverage levels in
infants and toddlers, a double-pronged
approach may be necessary to reduce
susceptibility to measles in youngchildren. On the one hand, delays in
vaccination will need to be tackled. This
must include addressing parental
concerns and physician knowledge to
ensure children are vaccinated in a
timely fashion in the absence of medical
contraindications.2830 Because delays
in primary vaccination in thefirst months
of life are associated with reduced vacci-
nation levels against measles, an inclusive
FIGURE 2Age-related coverageforMCV1 andMCV2for thestudycohort.Theearliest timepointat which vaccinationwouldbe consideredvalidand theoptimalvaccination
periods recommended (recom) in the Swiss vaccination plan areindicated by vertical bars.19 Recommended well-childvisits are indicated as shaded bars.20
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approach to immunization programs is
necessary.31,32
Conversely, changes to recommended
timing may have to be considered when
evaluating national immunization
schedules. System factors have been
suggested as potentially havinga impactcomparable to individual level risk fac-
tors on untimely vaccination.7,24 In our
cohort, acceleration in the rate of MCV2
vaccination could be observed during
months 19 and 25 of age corresponding
to 2 well-child visits within the recom-
mended time period (Fig 2). This finding
suggests that recommendations for a
specific time point rather than a time
period may lead to better adherence,
especially if the recommended timepoint corresponds to a scheduled well-
child visit. Parental satisfaction with
preventive pediatric care in early life
is associated with fewer immunization
delays.33 Structural features of health
care systems, in particular integration
with key components of primary care
such as well-child visits, thus seem to
encourage parents to accept timely
immunization and enable providers
to offer vaccinations when mostappropriate.7
In fact, the greatest impact on effective
population coverage among preschool-
aged children is achieved by early and
timely MCV1 administration. Assuming
waning immunity from maternal anti-
bodies at 6 months and 84.5% MCV1
vaccine effectiveness for 9 to 12 month-
olds,4 immunization of all children at
9 to 12 months with MCV1 and by
13 months with MCV2 would push the
effective vaccine coverage from 60%
to 80% in a group of 6- month-olds to
3-year-olds with uniform age distribu-
tion. Well-child visits in Switzerland are
recommended at 9 and 12 months of
age. It must therefore be consideredwhether adapted recommendations for
measles vaccination to mirror these
visits(MCV1 at 9 monthsand MCV2 at 12
months of age) may improve effective
coverage in children up to 2 years of
age. This change would shorten the
period children spend at risk for mea-
sles through improved timing of vacci-
nation. However, it would ensure that
2 definitive time points coinciding with
well-child visits are recommended,thereby potentially improving timeli-
ness of vaccination.
Several limitations must be considered
in this type of analysis. Out-of-pocket
payments for vaccination and incom-
plete submissions of invoices may have
led to differential misclassifications in
the vaccination status of some children.
Overall, the proportion of infants with
a high voluntary deductible was very
small (,
1%); therefore, most likelyclaims were made extensively where
applicable. Any children receiving vac-
cinations during an inpatient stay were
not identified as immunized in our
study. Because vaccination opportuni-
ties are known to be underused in the
hospital setting, the impact of this is
likely to be small.34 Lastly, patients join-
ing from other health insurance pro-
grams during the first 2 years of life
were not observed and may differ in
vaccination behavior from patients
who remain with the same insurer
throughout their early childhood.16
CONCLUSIONSFocusing on immunization against
measles,weofferevidenceinsupportof
incorporating data on timeliness of
vaccination in the evaluation of vaccine
coverage.The goodagreement between
our data and official estimates indi-
cates the validity of using health in-
surance data. Such an analysis, using
routinely collected information, may
also be less costly. Vaccine coverage,
timeliness, and patterns of vaccinationactivity in relation to age and recom-
mended schedules can all be identified.
To move toward the eradication of en-
demic measles in Switzerland, several
measures are necessary. First, pro-
moting acceptance of measles immu-
nizationwillhelptoachievehighratesof
vaccine uptake. Second, timely appli-
cation of measles immunization at the
individual level will reduce the time any
1 child spends susceptible to measles.This must include considerations re-
garding the ages at which measles vac-
cinations are recommended. Lastly, the
relationship with overall well-child care
must be considered to reduce system
barriers to optimal measles immuniza-
tion. Such barriers may be contributing
to the slow progress toward the elimi-
nationofendemic measles inSwitzerland
and in other similar settings.
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DOI: 10.1542/peds.2012-0132; originally published online August 20, 2012;2012;130;e600Pediatrics
Julia A. Bielicki, Rita Achermann and Christoph BergerTiming of Measles Immunization and Effective Population Vaccine Coverage
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