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UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl)
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Assessment of pharmacovigilance approaches for monitoring the safety of antimalarial drugsin pregnancy
Dellicour, S.O.M.C.
Link to publication
Citation for published version (APA):Dellicour, S. O. M. C. (2014). Assessment of pharmacovigilance approaches for monitoring the safety ofantimalarial drugs in pregnancy. Alblasserdam: Dutch University Press.
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Download date: 23 Oct 2020
7
Chapter1
GeneralIntroduction
Chapter 1
8
PharmacovigilanceAll drugs have the potential to cause harm and their risk‐benefit profiles need to be determined to
maximize therapeutic outcomes.[1] Attention to the importance of drug safety monitoring was
brought to light by the thalidomide tragedy in the 1960s.[2,3] Thalidomide was used as an
antiemetic and sedative which was considered safe including during pregnancy. More than 10,000
malformed children with phocomelia (with limbs severely underdeveloped or absent) were born
before a safety signal was identified and thalidomide was withdrawn.[4] This had a profound impact
on drug regulatory processes from registration to post‐marketing surveillance.[5]
Pharmacovigilance, sometimes referred to as drug monitoring or post‐marketing surveillance, is
defined by the World Health Organization (WHO) as “the science and activities relating to the
detection, assessment, understanding, and prevention of adverse reactions or any other possible
drug‐related problems”.[1] Fundamental aims are early detection of unknown safety issues,
quantifying risk and risk factors associated with adverse drug reactions (ADRs) and primarily
preventing unnecessary harm to patients.
Before a drug is marketed, drugs are tested pre‐clinically in‐vitro and in animal studies for toxicity. If
a compound passes these tests it goes through a series of clinical trials (see figure 1). Drug
regulatory authorities make their decision based on evidence regarding efficacy, safety and quality
deemed adequate for a drug to be approved. By the time a drug is marketed, information on safety
and efficacy has been derived from limited number of subjects (between 500‐5000) who are
typically carefully selected and followed under controlled conditions for a relatively short amount of
time.[6] This limits the possibility of detecting rare adverse events (the rule of three suggests that by
the time of registration, safety information is typically only available for adverse events occurring at
frequencies of 0.1 to 1%1[7]), or events with slow onset such as cancer or events occurring in
vulnerable groups such as pregnant women, children and the elderly or people with co‐morbid
conditions and concomitant medications which are usually excluded from pre‐registration clinical
trials.
Passive surveillance through spontaneous reporting is the backbone of post‐marketing surveillance.
This entails identification of a suspected ADR following drug exposure by healthcare professionals,
assessments of severity and causality and reporting according to standard procedures. Passive
surveillance is useful for hypothesis generation and identification of new safety signals but has its
limitations such as under‐reporting, variable quality and completeness of the reported
data, tendency for reporting of known reactions and false causality attribution.[8] Active surveillance
approaches are essential to assess and evaluate the nature and rates of adverse events as they can
provide denominator data. The most common pharmacovigilance active surveillance involves
identifying individuals exposed to a drug of interest and following them systematically to assess for
adverse events (e.g. Prescription Event Monitoring system used in the UK [9]). Other approaches
using pharmacoepidemiological methods, include cohort or case control designs, are used for safety
signal confirmation or characterization.[10,11] Deciding on an approach should be based on the
safety specification of a product and whether the purpose of the investigation is hypothesis or signal
1 The rule of three is commonly used in pharmacovigilance to estimate the sample size needed to detect adverse events. It
is based on the assumption that there is 95% chance of observing one occurence of an event in a population 3 times the size of the event’s rate (e.g. to pick up a rare event occuring at a rate of 1 /10 000, 30 000 individuals will need to be monitored to be 95% certain of detecting this event).
Introduction
9
generating; hypothesis strengthening or a confirmatory study, (i.e. evaluation of a known safety
signal).
Figure 1 Clinical development of medicines adapted from “WHO Policy Perspectives on Medicines — Pharmacovigilance: ensuring the safe use of medicines”.[6]
PharmacovigilanceinresourceconstrainedsettingsThe public health burden of ADRs and medication errors is difficult to quantify but it is likely to be
worse in resource constrained settings because of weak health systems, overstretched and often
inadequately trained healthcare staff, unreliable supply and quality of drugs, polypharmacy (use of
multiple drugs concomitantly), concomitant use of herbal remedies as well as availability of most
prescription drugs from the informal market.[12] Few low and middle‐income countries have
functioning national pharmacovigilance systems. Currently, less than 2% of ADR reports collated at
the Uppsala Monitoring Centre of the WHO Programme for International Drug Monitoring (UMC,
which collates reports from national pharmacovigilance centres globally [13]) come from low or
middle‐income countries.[14] Indeed, most of these countries make national treatment or
prevention policy decisions with reliance on drug safety data from industrialised countries where
pharmacovigilance systems and regulatory authorities are better established. However, this often
comes at the expense of no or limited safety data for drugs targeting tropical diseases which are
seldom encountered in these industrialised settings.
While there is increasing access to medicines to combat HIV, malaria and tuberculosis in the tropics,
systems are needed to assess the risk‐benefit balance of these much‐needed interventions.[15] Drug
safety monitoring cannot rely on passive spontaneous reporting systems for ADRs due to the
limitations mentioned above. Targeted pharmacovigilance approaches are required in situations
where no systematic recording of drug exposure and suspected ADRs exist particularly where health
resources are limited. Passive surveillance has been proposed at selected sentinel sites where
healthcare professionals are trained and incentivised to report suspected severe ADRs to specific
drugs of interest.[16] Building on existing infrastructure and surveillance systems or studies would
provide more cost‐effective ways to collect reliable and timely data. Demographic surveillance sites
Preclinical Animal Experiments
Phase I > Phase II > Phase IIPhase IV
Post Approval
Development
Registration
Post registration
Phase I20‐50 healthy volunteers to
gather preliminary data
Animal experiments for acute toxicity, organ damage, dose dependence,
metabolism, kinetics, carcinogenicity, mutagenicity & teratogenicity
Phase III250‐4000 varied patient groups to determine short term safety and
efficacy
Phase II150‐350 patient with disease to determine safety and dosage
Phase IVPost‐approval studies to
determine specific safety issues
Chapter 1
10
are increasingly being considered for use as platforms for post‐marketing surveillance. Such sites
monitor vital events (births, deaths and migration) through regular censuses of a pre‐defined
population (typically 2 to 4 times per year), most also have links to clinical and treatment data from
local health facilities. They have well‐defined and characterized populations, and are valuable to
monitor public health interventions where health information systems are weak as they provide
denominator data, a framework to identify specific groups (such as pregnant women or children)
outside the healthcare setting as well as human resources and infrastructure for research.[17] Five
African sites that are part of the International Network for the Continuous Demographic Evaluation
of Populations and Their Health (INDEPTH) are conducting Phase IV studies to monitor antimalarial
effectiveness and safety in “real life” settings.[18] Antimalarial safety is being monitored through a
Spontaneous Adverse Events Reporting System (passive surveillance) and Cohort Event Monitoring
(CEM; active surveillance). The spontaneous reporting system is being strengthened in the selected
sites ensuring health workers are sensitised and familiar with the ADR reporting procedures. CEM
protocols involve active follow up of patients prescribed antimalarials on days 3 and 7 following
treatment and systematic recording of all clinical events during that time. This enables the
characterisation of known ADRs in terms of incidence as a denominator is available (which is not the
case for systems based on spontaneous reporting) and identification of risk factors as well as
detection of unknown safety signals. Another approach is to capitalize on planned studies, such as
those conducted by the Malaria in Pregnancy Consortium (MiPc) and the ACT consortium (ACTc)
which have set up a centralized safety database collating ADRs collected across studies using
standardized reporting procedures and tools.[19,20] Such systems could then be extended to other
drugs and expanded to additional sites through new collaborations.
DrugsafetyinpregnancySpecial considerations apply to the assessment of drug safety in pregnancy, particularly for drugs
used to treat diseases that are only endemic in resource constrained settings. Most drugs are
marketed with limited information on their safety when used during pregnancy. Pre‐approval
studies have inherent limitations in determining the safety of drugs used during pregnancy. Animal
reproductive toxicology studies have ambiguous predictive value for human teratogenesis due to
variations in species‐specific effects [21] and pregnant women are routinely excluded from pre‐
licensure clinical trials for fear of harming the mother or the developing fetus.[22,23] Physiological
changes associated with pregnancy limit the inference of pharmacokinetic and pharmacodynamic
data from non‐pregnant subjects.[24] Consequently, most drugs are not recommended for use
during pregnancy due to the lack of information on their risk‐benefit profile. Yet drugs are widely
used by pregnant women. Medication often cannot be avoided for chronic diseases, such as asthma,
epilepsy, malignant diseases, HIV, or other illnesses which may harm the mother and the unborn
baby if left untreated. Furthermore, many women are likely to be inadvertently exposed to drugs at
the most vulnerable time of embryo development early in gestation before pregnancy status is
recognised. Healthcare providers, pregnant women and policy‐makers need valid information in
order to make informed decisions about the use of drugs during pregnancy.
Introduction
11
PharmacovigilanceapproachesfordrugsusedinpregnancyThere are several methodological challenges to the study of safety of drugs in pregnancy, including
those common to overall pharmacovigilance methods such as the need for large sample sizes to
minimise the possibility that the observed association between a drug and a rare outcome occurred
due to chance; the possibility of confounding by indication which implies studies should take into
account the contributing risk of the underlying maternal illness; the general lack of background rates
needed to put signals into context and the potential self‐referral bias introduced by voluntary
reporting.[25,26] Special considerations are also required for assessment of outcome and drug
exposure. Monitoring drug safety in pregnancy necessitates systematic recording of pregnancy
outcomes, examining the newborns and possibly following up the infants to detect anomalies not
detectable at birth. Where deliveries occur outside health facilities, as is the case in many rural
settings in low and middle income countries and particularly for early pregnancy loss, systems need
to be put in place to capture all pregnancy outcomes. Ascertainment of drug exposure requires
reliable information on the drug and gestational age at the time of exposure. This is important as the
impact on the fetus from drugs used in pregnancy depends on the stage of pregnancy at the time of
exposure as different tissues and organs have specific developmental timelines.[27,28] These
methodological considerations are described in detail in chapter 4 based on the case of artemisinin
combination therapies used for the treatment of malaria.
Passive surveillance (i.e. spontaneous reports of suspected ADRs) for detecting drug with potential
embryo‐fetal adverse effects relies on judicious clinicians to make the association between a drug
exposure in pregnancy and an adverse event which will often occur months and sometimes years
later (for congenital anomalies not detectable at birth). In resource constrained settings, such an
approach has limited use due to under‐ascertainment of outcomes such as miscarriages and birth
defects in communities where birth anomalies are considered taboos, as well as the general lack of
awareness around pharmacovigilance and the need to report suspected ADRs.
Pregnancy exposure registries, a type of cohort design, are the most common approach to monitor
drug safety in pregnancy in industrialised countries (e.g. the Antiretroviral Pregnancy Registry[29] or
the Antiepileptic Drug (AED) Pregnancy Registry[30]). The U.S. Food and Drug Administration (FDA)
and the European Medicines Agency (EMA) recommend pregnancy exposure registries for products
that are likely to be used during pregnancy or by women of reproductive age, particularly if there
have been case reports of adverse pregnancy outcomes following exposure, drugs in the same
pharmacological class are known to pose risk during pregnancy or pre‐clinical animal data suggests
potential teratogenic risk.[31,32] A pregnancy exposure registry involves active identification and
recruitment of pregnant women exposed to a drug or class of drug of interest and following these
women throughout pregnancy. This approach has many advantages such as active enrolment and
pregnancy outcome ascertainment to minimise loss to follow up, centralised and prospective
ascertainment of exposed pregnancies which reduces biases. Drawbacks of most pregnancy
registries are the limited sample size to detect moderate effects, the lack of outcome validation and
standardisation of birth defect assessments.[27] To overcome the sample size requirement
pharmacoepidemiologic studies using existing databases are often used in high income countries.
Cohort studies use large databases such as medical insurance claim databases (e.g. the Medicaid
database in the US[33]), electronic medical records (e.g. GPRD in the UK[34]), or data from
teratology information services (e.g. the Motherisk Program in Canada[35]). Birth defect registries
and case‐control surveillance systems are also used to assess associations between medications and
Chapter 1
12
congenital malformations (e.g. the Birth Defects Study by Slone Epidemiology Centre[36]).
Applicability of these methods in low and middle income countries is unknown.
Malariainpregnancy
EpidemiologyandburdenMalaria is a major public health problem affecting an estimated 3.4 billion people worldwide (half of
the world’s population) which live in areas at risk of malaria. In 2012, an estimated 207 million cases
of malaria occurred globally, resulting in over half a million deaths.[37] This life threatening disease
is preventable and treatable through proper use of antimalarial drugs, insecticide treated bednets
and indoor residual spraying of insecticides. Since 2000, a significant decrease in malaria mortality
rates have been observed due to the vast increase in the financing and coverage of malaria control
programmes.[37]
Pregnant women and children under five are most at risk of malaria. Malaria in pregnancy (MiP) can
have devastating consequences for the mother and fetus, including severe maternal anaemia and
mortality, miscarriage, intrauterine growth retardation and low birthweight (LBW), preterm birth
and stillbirth.[38,39] It is estimated to cause as many as 900,000 low birth weight births, and
100,000 infant deaths every year. Furthermore, up to a quarter of maternal mortality in endemic
countries could be attributable to malaria.[39,40,41,42,43]
PreventionguidelinesWHO recommends two approaches for the prevention of MiP in areas with stable malaria
transmission (where the population is exposed to a fairly constant, high rate of malaria infected
mosquito bites [>10 per person per year]): intermittent preventative treatment in pregnancy (IPTp)
with sulfadoxine‐pyrimethamine (SP) at each antenatal clinic visit following quickening and the use
of insecticide‐treated bed nets (ITNs) to protect pregnant women from the bites of infected
mosquitoes.[44,45] Coverage with these prevention strategies remains very low. In 2007 it was
estimated that only about 39% and 25% of pregnant women in sub‐Saharan Africa used ITNs and
received at least two doses of IPTp, respectively.[46]
TreatmentguidelinesPregnant women, when infected, require rapid diagnosis and case management with safe and
effective antimalarial drugs to prevent progression to severe disease or death, or to prevent
asymptomatic infections from becoming chronic leading to fetal growth restriction and malaria‐
related maternal anaemia.[38,39] Established antimalarials like chloroquine and SP are no longer
recommended for the case management of malaria illness due to drug resistance of the parasite.
Artemisinin‐based combination therapies (ACTs) are now the recommended treatment for
uncomplicated malaria in sub‐Saharan Africa.[47] Artemisinin derivatives have been used for
centuries in China but they have only been deployed for use as ACTs since 2001.[47,48] Based on the
level of drug resistance to the partner medicine, the following fixed‐dose combination ACTs are
recommended: artemether plus lumefantrine; artesunate plus amodiaquine; artesunate plus
mefloquine; artesunate plus SP and dihydroartemisinin plus piperaquine.
In the first trimester of pregnancy an ACT is indicated only if an alternative antimalarial is not
immediately available, or if treatment with 7‐day quinine (without, or combined with, clindamycin)
fails or there is uncertainty of compliance with the 7‐day quinine regiment. The recommendation for
treatment of pregnant women with severe malaria includes parenteral artesunate because it is
Introduction
13
faster acting than parenteral quinine and is associated with improved survival in patients with severe
malaria.[49,50,51]
Antimalarialsafetyinpregnancy
AntimalarialsconsideredsafethroughoutpregnancyAntimalarials recommended for pregnant patients must be safe for the mother and her unborn
baby. There is insufficient information on the safety of most antimalarials in pregnancy, particularly
for exposure in the first trimester. A retrospective study in Thailand, reported the deleterious effect
of even a single episode of malaria in the first trimester and its association with an increase in the
risk of miscarriage, emphasising the need for safe and efficacious drugs in this critical period.[52]
This is further supported by a recent modelling study reporting that up to two thirds of placental
infections occur by the end of the first trimester.[43] Antimalarial medicines considered safe in the
first trimester of pregnancy are quinine (with or without clindamycin), chloroquine, proguanil and
more recently mefloquine although this is based on limited evidence. As mentioned above,
chloroquine is no longer recommended for treatment of falciparum malaria. Proguanil and
chlorproguanil although deemed very safe in pregnancy, have limited value in resource constrained
settings as the current formulations available are either too expensive (atovaquone‐proguanil) or
carries the risk of acute haemolysis in patients with glucose‐6‐phosphate dehydrogenase (G6PD)
deficiency (which has a prevalence of up to 30% in some African countries[53]) when in combination
with dapsone. This combination is no longer available since its marketing authorization holder
withdrew it from the market in 2008.[54] Animal studies (in rodents, dogs and primates) did not find
quinine to have embryo‐fetal toxicity except one study which reported congenital malformations in
5% of pups born to rats receiving quinine.[55,56,57] There was no evidence of embryo‐fetal toxicity
in published human data. Quinine is often thought to have abortifacient properties at high dosage.
The author of a commonly cited publication from 1908 reports the beneficial effect of quinine as “It
may be laid down as an almost invariable rule that if in a pregnant woman suffering from malarial
fever uterine action has begun, the quinine will probably hasten the abortion; but that if uterine
action has not begun, it will not start it, but will, on the contrary, probably be the means of saving
the pregnancy”.[58] A recent observational study in Tanzania reported an increased risk of
pregnancy loss in women exposed to quinine in the first trimester [59] however it is not clear
whether the observed effect could be explained by the underlying malaria infection, especially
because of the potential for poor compliance with the 7‐day quinine regimen given the poor
tolerability of quinine due to cinchonism (a syndrome which includes symptoms of ringing of the
ears, blurred vision, headache, nausea and dizziness) and hypoglycaemia.[60,61] Mefloquine has
been recommended as a prophylactic for pregnant travellers by WHO and CDC. Recently after
review of existing evidence the FDA and CDC changed their recommendation for the use of
mefloquine in pregnancy both as a prophylactic and for treatment.[62] Mefloquine has an
acceptable reproductive toxicity profile in animal studies at standard doses and data on 1000 first
trimester exposures suggests no increase in risk to adverse pregnancy outcomes. Although 1
retrospective study found an increase in the risk of stillbirths associated with mefloquine treatment
doses in pregnancy this finding has not been confirmed by subsequent studies.[60,61,63] The result
of a multi‐centre randomised controlled trial in over 4000 second and third trimester pregnant
women did not find an increased risk of stillbirth with two or three 15 mg/kg treatment doses of
mefloquine compared to SP when used as IPTp. However tolerability was low, even when 15 mg/kg
Chapter 1
14
was given as a split dose over two days, with 30% of pregnant women reporting vomiting and
dizziness which could limit the use of mefloquine for IPTp.[64]
AntimalarialscontraindicatedinthefirsttrimesterofpregnancySP, which has limited use due to increasing drug resistance, is still used for the prevention of malaria
in pregnancy through IPTp in most areas with high malaria transmission. As an anti‐folate it is not
recommended in the first trimester of pregnancy due to risk of neural tube defects.[65] Animal
studies found embryotoxicity at high doses including cleft palate in rat models.[66] Documented use
in over two thousand pregnancies in the second and third trimester of pregnancy found no evidence
of embryotoxicity.[60,61] Amodiaquine is considered safe in pregnancy although there are neither
documented data on exposure in the first trimester of pregnancy nor animal reprotoxicology
studies.[67,68] Lumefantrine is only available as an ACT in combination with artemether which is
contraindicated in the first trimester of pregnancy (see below) and data from animal studies did not
show any embryotoxic effect.[60,61] Piperaquine, which is also only available as an ACT, has a safety
profile expected to be similar to that of chloroquine. Animal reprotoxicology studies of piperaquine
found no safety concerns except that gestation was prolonged in exposed rats.[69,70] The few
studies on the use of the combination dihydroartemisinin‐piperaquine in second and third trimesters
of pregnancy reported favourable outcomes for pregnant women.[71,72,73] Further trials are
underway with women in their second and third trimesters.[74,75,76,77,78]
ArtemisininderivativesinearlypregnancyAlthough ACTs are highly effective in treating malaria the safety of artemisinin derivatives during
early pregnancy remains to be determined. Animal reprotoxicology studies showed that artemisinin
derivatives have embryotoxic effects in all species studied (i.e. rat, rabbit and monkey) at low dose
ranges.[79,80] Pre‐clinical studies showed that the mechanism of embryotoxicity was through insult
to immature red blood cells (primitive erythroblasts) causing severe anaemia in the embryo and
leading to either embryolethality or malformations, skeletal (shortened or bent long bones and
scapulae, misshapen ribs, cleft sternebrae and incompletely ossified pelvic bones) and
cardiovascular (ventricular septal and vessel defects).[79,81] These studies also predicted that the
main window for insult to the fetus will occur early in pregnancy (between 4 and 10 weeks post
conception).[79] This is the period when the nucleated, metabolically active primitive erythroblasts
predominate in the blood. However, the exact moment when humans are most sensitive is unknown
as the primitive erythroblasts are gradually replaced by enucleated mature erythrocytes (which are
less sensitive to the effects of artemisinins) over several weeks. Information regarding risks
associated with the use of antimalarials in pregnancy in humans is sparse. Although the limited data
on human exposures is reassuring for first trimester exposures 2 , further information is
required.[61,82,83] With the widespread deployment of ACTs, the potential for inadvertent
exposure early in pregnancy is high when neither the physician nor the patient is aware of the
pregnancy.
It is essential to study the risks of artemisinins and ACT drugs in early pregnancy, and that vigilant
attempts are made to establish systems for the systematic collection of pregnancy‐drug exposure
data. It is unknown how best this can achieved in resource constrained malaria endemic countries.
The specialized nature of the reliable assessment of drug exposures, pregnancy outcome and
2 At the time of the first review in chapter 2 there were 123 documented exposures this number is now close to 760 as discussed in the last chapter of this thesis.
Introduction
15
malformations is not easily achievable from routine surveillance systems such as national
pharmacovigilance programmes, where they exist, and will require sentinel sites with enhanced
active surveillance or dedicated studies, good record keeping and follow‐up systems, and training of
staff to examine newborns.
ThesisAimandOutlineThe aim of this thesis is to develop and evaluate such targeted pharmacovigilance systems to assess
the safety of the ACTs in early pregnancy.
This thesis is divided into two components: desk‐based reviews (chapters 2‐4) and field‐based
studies (chapters 5‐8) with the overall aim to assess pharmacovigilance approaches to provide better
estimates of the risk‐benefit profiles of ACTs used in early pregnancy.
Objectivesandoutline1) Review existing evidence on human exposure to ACTs in pregnancy with the emphasis on
first trimester exposures (chapter 2)
2) Derive global estimates of the number of pregnancies at risk of malaria based on a
contemporary map of malaria transmission and demographic data for pregnancy and
fertility rates to provide an estimate of the scale of the problem posed by MiP (chapter 3)
3) Describe the methodological considerations for setting up antimalarial pregnancy exposure
registries in resource constrained settings (chapter 4)
4) Assess the feasibility of record linkage using routinely collected healthcare data as a
pragmatic means of monitoring antimalarial safety in early pregnancy. A study involving
extraction of data from health records from a dispensary in south‐western Senegal is
reported (chapter 5)
5) Explore community perceptions of miscarriage and congenital anomalies. Findings from 10
focus group discussions carried out in western Kenya are described which provide insight
for studies of pregnancy outcomes in similar rural African settings (chapter 6)
6) Assess prescribing behaviour and knowledge of malaria treatment guidelines for pregnant
women among healthcare providers and drug outlet dispensers in an area of high malaria
transmission. The results from a cross‐sectional survey in rural western Kenya are
presented providing insight on the scale of ACT prescribing in early pregnancy (chapter 7)
7) Assess the risk of miscarriage associated with exposure to ACTs in the first trimester of
pregnancy. The findings from a prospective cohort study of women of childbearing age in
Western Kenya are presented (chapter 8)
8) Draw conclusions on the potential of the proposed pharmacovigilance approaches for drugs
used by woman of childbearing age and pregnant women in resource constrained settings
based on all the evidence presented in this thesis (chapter 9)
Descriptionofstudysites
SenegalThe study described in chapter 5 took place in a private mission dispensary based in Mlomp, a village
of approximately 8,000 inhabitants in the District of Oussouye, Casamance, south‐western Senegal.
The dispensary offers outpatient, antenatal clinic (ANC running once a week), and maternity (since
1968) services. The dispensary is well attended, offers high quality services and is equipped to
perform simple laboratory tests including microscopy evaluations of malaria slides. Dispensary
Chapter 1
16
registers for antenatal care, delivery, child welfare clinics and a general register for outpatient visits
have been meticulously kept since 1993. Nearly all pregnant women attend ANC and health facility
deliveries have increased from 50% in 1961 to 99% in 1999. [84,85] The district hospital is situated in
Oussouye (the closest town) about 10km away with limited public transport option and the regional
hospital is in Ziguinchor (about 50km away).
Malaria occurs year‐round and peaks during the rainy season (July to December) in this area. A
recent study showed that malaria transmission intensity in southern Senegal has been decreasing
significantly in the past 15 years.[86] The area is rural, there is no running water or electricity and
rice cultivation is the main economic activity. Mlomp has been under yearly demographic
surveillance by the French National Institute of Demographic Studies (INED) since 1985.[87] Several
research studies on malaria and malaria chemotherapy have been conducted in the study
area.[88,89,90,91]
This setting, with a relatively enclosed population and comprehensive records on malaria episodes,
treatment and pregnancy outcomes, provided a good opportunity to pilot utilisation of routine
healthcare data for monitoring antimalarial safety in pregnancy.
Figure 2. Study site in south‐western Senegal (study presented in chapter 5).
KenyaStudies described in chapters 6 to 8 were conducted within the Health and Demographic
Surveillance System (HDSS) in western Kenya under a long‐standing collaboration between the
Kenya Medical Research Institute (KEMRI) and the US‐based Centers for Disease Control and
Prevention (CDC).[92,93] The HDSS operates a quarterly survey covering an area of about 700 km2
and 225,000 people living in 385 villages. Data on pregnancies, births, deaths, cause of deaths via
verbal autopsies and migrations are collected.[94] This is an integrated field site designed to manage
the longitudinal follow up of residential units, households and individuals. The field operations also
involve surveillance of paediatric out‐patient visits in peripheral health facilities, and monitoring of
paediatric in‐patient visits at two District Hospitals. In addition, household socioeconomic and
Introduction
17
educational status surveys are conducted annually to complement the morbidity and demographic
data. Extensive laboratory facilities have been established to support diagnostic work in parasitic
and bacterial diseases as well as HIV; basic immunology and molecular biology research in these
areas is also conducted. The centre has conducted a number of large studies and trials (e.g., the
large community‐based, group‐randomised, controlled trial of permethrin‐treated bed nets (ITNs)
carried out between 1996 ‐1999, the Phase 3 trial of the RTS,S malaria vaccine and a Phase 2B trial of
a tuberculosis vaccine, among others).
Malaria transmission is perennial and holo‐endemic, although transmission has been greatly reduced
following provision of free ITNs.[95,96] The prevalence of malaria among individuals over 15 years of
age ranged between 10–20% in the period 2006 to 2008. [KEMRI/CDC, unpublished observations]
There is a high rate of HIV infection (in 2008: 15.4% overall: 20.5% among females and 10.2% among
males while the National HIV prevalence is around 7%).[97] The prevalence of TB in individuals over
15 years of age was 600/100,000 and geohelminth prevalence in pregnant women was recorded to
be as high as 76.2%.[98,99] Consequently, the area has mortality figures that reflect this burden of
infectious diseases ‐ infant mortality rate of 111 per 1,000 live births and a life expectancy at birth of
45 years in 2008.[93] The maternal mortality ratio is 669 per 100,000 live births which is higher than
the national estimate of 488 per 100,000 live births reported by the Kenya Demographic and Health
Survey in 2008/2009 for approximately the same time period.[100]
Nyanza Province
Figure 3. Study sites in western Kenya part of the KEMRI/CDC Health and Demographic Surveillance sites (studies presented in Chapters 6‐8).
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