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

Abstract

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.

Vaccinating pregnant women against influenza needs to be a priority for all countries: An expert commentary

“…Most studies have shown that the antibody response to influenza vaccine is similar in pregnant and non-pregnant women (Haberg et al, 2013;Mak et al, 2008), although there is some debate as to the optimal timing of vaccination in pregnancy. A meta-analysis of 16 studies found that the response to influenza vaccination was 1.33-1.96-fold higher in women vaccinated during the third trimester of pregnancy than at earlier time points, with evidence suggesting that vaccination later in pregnancy increased antibody transfer to the foetus by 1.21-1.64-fold (Cuningham et al, 2019). However, earlier vaccination provides longer protection against influenza for the pregnant woman, and averting infection early in pregnancy may have positive benefits for the foetus.…”

Influenza Vaccination Experiences of Pregnant Women as a Predictor of the Intention to Become Vaccinated in Future Pregnancies in Spain

“…More research studies on this subject could result in the development of future recommendations about the optimal period of time for immunization, (pre-conception, during pregnancy or postpartum) and the most cost-effective professionals, not only in the vaccination, but also in the monitoring and advice phases [ 44 , 45 ].…”

Vaccination during pregnancy: current and possible future recommendations

“…A recently published systematic review and meta-analysis found that vaccinating women later in pregnancy, at least 15 days before delivery, results in higher influenza-specific maternal antibody concentrations at birth and thus transfer of more antibodies to the unborn child. On the other hand, vaccinating earlier in pregnancy will provide protection against influenza during a longer proportion of the pregnancy, which is beneficial for the pregnant women, but may increase the probability that protection does not last until delivery and that consequently protection is not transferred to the offspring [66]. Additionally, safety data on influenza vaccination during the first trimester of pregnancy are lacking.…”