Abstract
ObjectiveTo describe the effect of maternal vaccination on birth outcomes in rural Nepal, modified by timing of vaccination in pregnancy and influenza virus activity.MethodsA secondary analysis was conducted using data from two annual cohorts of a randomized controlled trial. A total of 3693 pregnant women from Sarlahi District were enrolled between April 25, 2011, and September 9, 2013. All participants were aged 15–40 years and received a trivalent inactivated influenza vaccine or placebo. The outcome measures included birth weight, pregnancy length, low birth weight (<2500 g), preterm birth, and small‐for‐gestational‐age birth.ResultsData were available on birth weight for 2741 births and on pregnancy length for 3623 births. Maternal vaccination increased mean birthweight by 42 g (95% confidence interval [CI] 8–76). The magnitude of this increase varied by season but was greatest among pregnancies with high influenza virus circulation during the third trimester. Birth weight increased by 111 g (95% CI −51 to 273) when 75%–100% of a pregnancy's third trimester had high influenza virus circulation versus 38 g (95% CI −6 to 81) when 0%–25% of a pregnancy's third trimester had high influenza virus circulation. However, these results were nonsignificant.ConclusionSeasonal maternal influenza vaccination in rural Nepal increased birth weight; the magnitude appeared larger during periods of high influenza virus circulation.ClinicalTrials.gov NCT01034254.
Highlights
In 2010, influenza infection accounted for 19 200 000 disability- adjusted life years worldwide.[1]
When stratifying by timing of vaccination in pregnancy, an increase in birth weight was seen in each category, but was only statistically significant among women vaccinated before 26 weeks (48 g, 95% CI 6–90) (Table 4)
A statistically significant increase in pregnancy length was found among mothers who were vaccinated between 26 weeks and less than 30 weeks, when at least half of their third trimester had been exposed to high influenza virus circulation
Summary
In 2010, influenza infection accounted for 19 200 000 disability- adjusted life years worldwide.[1]. Observational studies and randomized controlled trials (RCTs) exploring the effect of maternal influenza vaccination on rates of SGA and preterm delivery have reported mixed findings.[10,11,12,13,14,15] The Nepal Mothers’ Gift Trial was an RCT of maternal influenza vaccination with two annual cohorts of pregnant women residing in a rural area of this country.[15,16] The primary outcomes were maternal influenza-like illness, infant influenza infection, and low birth weight (LBW; defined as
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