Abstract
Standardized case definitions strengthen post-marketing safety surveillance of new vaccines by improving generated data, interpretation and comparability across surveillance systems. The Global Alignment of Immunization Safety Assessment in Pregnancy (GAIA) project developed standardized case definitions for 21 key obstetric and neonatal terms following the Brighton Collaboration (BC) methodology.In this prospective cohort study, we assessed the applicability of GAIA definitions for maternal immunization exposure and for low birth weight (LBW), preterm birth, small for gestational age (SGA), stillbirth, neonatal death, neonatal infection, and congenital microcephaly. We identified the missing data elements that prevented identified cases and exposures from meeting the case definition (level 1–3 of BC diagnostic certainty). Over a one-year period (2019–2020), all births occurring in 21 sites (mostly secondary and tertiary hospitals) in 6 Low Middle Income Countries and 1 High Income Country were recorded and the 7 perinatal and neonatal outcome cases were identified from routine medical records. Up to 100 cases per outcome were recruited sequentially from each site.Most cases recruited for LBW, preterm birth and neonatal death met the GAIA case definitions. Birth weight, a key parameter for all three outcomes, was routinely recorded at all sites. The definitions for SGA, stillbirth, neonatal infection (particularly meningitis and respiratory infection) and congenital microcephaly were found to be less applicable. The main barrier to obtaining higher levels of diagnostic certainty was the lack of sonographic documentation of gestational age in first or second trimester. The definition for maternal immunization exposure was applicable, however, the highest level of diagnostic certainty was only reached at two sites. Improved documentation of maternal immunization will be important for vaccine safety studies. Following the field-testing of these 8 GAIA definitions, several improvements are suggested that may lead to their easier implementation, increased standardization and hence comparison across studies.
Highlights
Immunization during pregnancy can protect the pregnant woman and her child, both in the womb and in early life by increasing the antibody titers against vaccine-preventable diseases [1,2]
In this prospective cohort study, we assessed the applicability of GAIA definitions for maternal immunization exposure and for low birth weight (LBW), preterm birth, small for gestational age (SGA), stillbirth, neonatal death, neonatal infection, and congenital microcephaly
We developed algorithms for the GAIA definitions for LBW [19], preterm birth [20], SGA [21], stillbirth [22], neonatal death [18], neonatal infection (bloodstream infection (BSI), respiratory infection, meningitis) [23], postnatally diagnosed congenital microcephaly [24] and maternal immunization [18] to assess the level of diagnostic certainty of the GAIA definition met by recruited cases, if any
Summary
Immunization during pregnancy can protect the pregnant woman and her child, both in the womb and in early life by increasing the antibody titers against vaccine-preventable diseases [1,2]. Immunization in pregnancy is a key strategy to prevent significant morbidity and mortality amongst young infants globally. Implementation or strengthening of pertussis and influenza immunization of pregnant women holds great promise as a strategy to protect infants from these infections [4,5,6]. This is of specific interest for Low and Middle-Income Countries (LMICs), where access to basic health services may be limited and the burden of vaccine-preventable diseases is large [7]
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