Maternal-Birth Cohorts Assessing Influenza Immunity: A Scoping Review

Background/Objectives: Maternal-birth cohort studies are critical epidemiologic tools to assess patterns, breadth, and duration of immunity derived from influenza vaccines, natural infections, and maternal immunologic contributions. Historically, this study design has been important to the development of well-designed pediatric vaccines. We systematically reviewed international influenza maternal-birth cohort studies to discern commonalities and gaps in their approaches to evaluating influenza immune development. Methods: We performed a scoping review of published maternal-birth cohorts studying influenza virus infections and immunity. Principal themes included, a.) incidence rates and percentages of acute respiratory and influenza infections, b.) sample collection methods, c.) laboratory methods and diagnostic tests, d.) symptomatology and asymptomatic infections, e.) medically attended infections, f.) maternal and child vaccination status, g.) maternal samples and obstetric history, and h.) reported sources of cohort funding. Results: Nine cohorts met the inclusion criteria and were selected for review. Only two cohorts were conducted in countries classified as lower-middle income, and none were conducted in low-income countries. Syndromic definitions, statistical measures, specimen types, and laboratory techniques differed greatly across these cohorts. Most of these cohorts relied on governmental funding. Conclusions: The resource- and time-intensive information obtained from each of these cohorts independently contributes valuable knowledge to the study of influenza exposures and immunity. However, cross-cohort comparisons and analyses are challenged by methodologic variability. Scientific knowledge could be improved by including cohorts of infants at high risk of negative influenza outcomes, by purposeful standardization of core data element collection, timing, and procedures, by standardized analytic measurements, and coordinated reporting of results of scientific interest.