Influenza vaccination during pregnancy for prevention of influenza confirmed illness in the infants: A systematic review and meta-analysis

Abstract

Infants younger than 6 months of age are at particular risk for serious illness from influenza infection. Currently available influenza vaccines are, however, not licensed for use in infants <6 months old. Influenza vaccination during pregnancy elicits robust antibody responses in the women that will protect the infants against influenza infection during the first few months of life. We aimed to determine the impact of influenza vaccination during pregnancy to prevent laboratory-confirmed influenza infection and influenza-associated hospitalisations in infants <6 months old. An electronic search identified all studies assessing the proposed outcomes in infants after administration of influenza vaccine during pregnancy. Two meta-analyses were performed accordingly to studies restricting the evaluation to influenza-associated hospitalisations or not. Four randomized control trials and 3 observational studies reported on the prevention of laboratory-confirmed influenza infection in infants <6 months old. Maternal influenza vaccination was associated with a 48% [95% confidence interval (CI): 33 to 59] reduced risk of infants having laboratory-confirmed influenza infection. Four observational studies reported on the prevention of hospitalizations associated with laboratory-confirmed influenza infection and the pool estimate was 72% (95%CI: 39% to 87%). Receipt of influenza vaccine during pregnancy was associated with decreased risk of laboratory-confirmed influenza infection in the infants.

Keywords: immunization; infants; influenza; influenza infection; laboratory-confirmed; pregnancy.

Figure 1.

Flow diagram of included and excluded studies. Of 764 citations, 31 full articles were reviewed to determine eligibility for inclusion, and 9 studies were included in the meta-analyses.

Figure 2.

Forest plot of influenza vaccination during pregnancy in preventing laboratory-confirmed influenza infection in infants younger than 6 months stratified by study type. RCT: Randomized control trials.

Figure 3.

Forest plot of influenza vaccination during pregnancy in preventing hospital admissions with laboratory-confirmed influenza in infants younger than 6 months.