Maternal influenza and birth outcomes: systematic review of comparative studies

Fell, Deshayne B.; Savitz, D. A.; Kramer, Daniel; Gessner, BD; Ma, Katz; Knight, Marian; Luteijn, Michiel; Marshall, Helen; Bhat, Niranjan; Gravett, MG; Skidmore, Becky; Ortiz, Justin R.

doi:10.1111/1471-0528.14143

Cited by 131 publications

(125 citation statements)

References 90 publications

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“…The risks of hospitalisation and complications for respiratory illness during the influenza season are higher for pregnant women and increase by trimester . Furthermore, pregnant women infected with influenza might be more likely to have adverse birth outcomes …”

Section: Introductionmentioning

confidence: 99%

Optimal timing of influenza vaccine during pregnancy: A systematic review and meta‐analysis

Cuningham

Geard

Fielding

et al. 2019

Influenza Resp Viruses

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Background Pregnant women have an elevated risk of illness and hospitalisation from influenza. Pregnant women are recommended to be prioritised for influenza vaccination during any stage of pregnancy. The risk of seasonal influenza varies substantially throughout the year in temperate climates; however, there is limited knowledge of how vaccination timing during pregnancy impacts the benefits received by the mother and foetus. Objectives To compare antenatal vaccination timing with regard to influenza vaccine immunogenicity during pregnancy and transplacental transfer to their newborns. Methods Studies were eligible for inclusion if immunogenicity to influenza vaccine was evaluated in women stratified by trimester of pregnancy. Haemagglutination inhibition (HI) titres, stratified by trimester of vaccination, had to be measured at either pre‐vaccination and within one month post‐vaccination, post‐vaccination and at delivery in the mother, or in cord/newborn blood. Authors searched PubMed, Scopus, Web of Science and EMBASE databases from inception until June 2016 and authors of identified studies were contacted for additional data. Extracted data were tabulated and summarised via random‐effect meta‐analyses and qualitative methods. Results Sixteen studies met the inclusion criteria. Meta‐analyses found that compared with women vaccinated in an earlier trimester, those vaccinated in a later trimester had a greater fold increase in HI titres (1.33‐ to 1.96‐fold) and higher HI titres in cord/newborn blood (1.21‐ to 1.64‐fold). Conclusions This review provides comparative analysis of the effect of vaccination timing on maternal immunogenicity and protection of the infant that is informative and relevant to current vaccine scheduling for pregnant women.

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Section: Introductionmentioning

confidence: 99%

Optimal timing of influenza vaccine during pregnancy: A systematic review and meta‐analysis

Cuningham

Geard

Fielding

et al. 2019

Influenza Resp Viruses

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“…These efforts have led to recent publications from LMICs, supported by WHO, that provide important influenza disease burden data ( 34 ). WHO has also sponsored reviews of influenza-associated disease burden among pregnant women and their infants ( 35 , 36 ). Additional multinational collaborations are under way that will continue to develop more credible global influenza mortality and hospitalization estimates based on recent work to develop national estimates, as well as information on influenza burden among key high-risk groups (Figure) ( 6 ).…”

Section: Ongoing Work To Address the Gaps And Future Needsmentioning

confidence: 99%

Progress and Remaining Gaps in Estimating the Global Disease Burden of Influenza

Bresee¹,

Fitzner²,

Campbell³

et al. 2018

Emerg. Infect. Dis.

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Influenza has long been a global public health priority because of the threat of another global pandemic. Although data are available for the annual burden of seasonal influenza in many developed countries, fewer disease burden data are available for low-income and tropical countries. In recent years, however, the surveillance systems created as part of national pandemic preparedness efforts have produced substantial data on the epidemiology and impact of influenza in countries where data were sparse. These data are leading to greater interest in seasonal influenza, including implementation of vaccination programs. However, a lack of quality data on severe influenza, nonrespiratory outcomes, and high-risk groups, as well as a need for better mathematical models and economic evaluations, are some of the major gaps that remain. These gaps are the focus of multilateral research and surveillance efforts that will strengthen global efforts in influenza control in the future.

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“…Third, Hutcheon et al also concluded that the observed fetal benefits of maternal influenza immunization are biologically implausible, and they supported this claim with a forthcoming (unpublished) systematic review in which minimal support for a strong association between maternal influenza illness and adverse birth outcomes was found (9). We disagree; not only is biological plausibility among the least important of the classic Bradford Hill criteria for assessing causality (17), but the conclusion reached by Hutcheon et al ignores compelling empirical evidence to the contrary.…”

mentioning

confidence: 95%

“…These differences might be particularly pronounced when comparing findings between geographic regions because climate, socioeconomic and nutritional status, and the baseline risk of adverse outcomes may all influence disease epidemiology. For their sample size calculations, Hutcheon et al used published estimates of influenza incidence and preterm birth rates (see Web Table 1 of their article), as well as measures of the association between maternal influenza illness and preterm birth calculated from previous observational studies (9). These estimates were derived almost entirely from studies conducted in temperate climates (predominantly the United States and Canada) with relatively short influenza seasons and low baseline rates of adverse birth outcomes.…”

mentioning

confidence: 99%

“…There is in fact substantial evidence supporting the important role of infection and systemic inflammation in the causal pathway of preterm birth (18). Indeed, the authors of a recent systematic review of studies of the association between maternal influenza and birth outcomes (including several co-authors of the paper by Hutcheon et al) reported adjusted odds ratios for preterm birth of 2.4 and 4.0 in 2 studies of severe 2009 H1N1 influenza during pregnancy; these studies were deemed in that analysis to be of the “highest methodological quality” (9). Furthermore, the results of multiple well-designed studies, including publicly available data from recent RCTs, have been excluded from their analysis, ostensibly because they are implausible on purely hypothetical grounds.…”

mentioning

confidence: 99%

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Maternal Influenza Immunization and Adverse Birth Outcomes: Using Data and Practice to Inform Theory and Research Design

Phadke

Steinhoff²,

Omer

et al. 2016

Am. J. Epidemiol.

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Maternal influenza immunization can reduce influenza-attributable morbidity and mortality among pregnant women and infants who are too young to be vaccinated. Data from empirical studies also support the hypothesis that immunization can protect the fetus against adverse outcomes if the mother is exposed to influenza. In their theoretical analysis in the Journal, Hutcheon et al. (Am J Epidemiol. 2016;184(3):227–232) critiqued the existing evidence of the fetal benefits of maternal influenza immunization by calculating the sample sizes needed to demonstrate hypothetical reductions in risk and concluded that the benefits observed in empirical studies are likely implausible. However, in their analysis, they did not take into account multiple fundamental characteristics of influenza epidemiology, including the time-variable effects of influenza illness and vaccination during pregnancy, or well-known differences in disease epidemiology between seasons, populations, and geographic regions. Although these and other factors might affect the magnitude of fetal benefit conferred by maternal influenza immunization, studies in which investigators have accounted for influenza circulation have demonstrated a consistent protective effect against a variety of adverse birth outcomes; those studies include the only randomized controlled trial designed a priori and adequately powered to do so. Only a comprehensive and nuanced assessment of the evidence base will allow for effective translation of these data into a global immunization policy.

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Maternal influenza and birth outcomes: systematic review of comparative studies

Cited by 131 publications

References 90 publications

Optimal timing of influenza vaccine during pregnancy: A systematic review and meta‐analysis

Optimal timing of influenza vaccine during pregnancy: A systematic review and meta‐analysis

Progress and Remaining Gaps in Estimating the Global Disease Burden of Influenza

Maternal Influenza Immunization and Adverse Birth Outcomes: Using Data and Practice to Inform Theory and Research Design

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