Association of influenza vaccination during pregnancy with birth outcomes in Nicaragua

Abstract

Background: Studies have shown that influenza vaccination during pregnancy reduces the risk of influenza disease in pregnant women and their offspring. Some have proposed that maternal vaccination may also have beneficial effects on birth outcomes. In 2014, we conducted an observational study to test this hypothesis using data from two large hospitals in Managua, Nicaragua.Methods: We conducted a retrospective cohort study to evaluate associations between influenza vaccination and birth outcomes. We carried out interviews and reviewed medical records post-partum to collect data on demographics, influenza vaccination during pregnancy, birth outcomes and other risk factors associated with adverse neonatal outcomes. We used influenza surveillance data to adjust for timing of influenza circulation. We assessed self-reports of influenza vaccination status by further reviewing medical records of those who self-reported but did not have readily available evidence of vaccination status. We performed multiple logistic regression (MLR) and propensity score matching (PSM).Results: A total of 3268 women were included in the final analysis. Of these, 55% had received influenza vaccination in 2014. Overall, we did not observe statistically significant associations between influenza vaccination and birth outcomes after adjusting for risk factors, with either MLR or PSM. With PSM, after adjusting for risk factors, we observed protective associations between influenza vaccination in the second and third trimester and preterm birth (aOR: 0.87; 95% confidence interval (CI): 0.75–0.99 and aOR: 0.66; 95% CI: 0.45–0.96, respectively) and between influenza vaccination in the second trimester and low birth weight (aOR: 0.80; 95% CI: 0.64–0.97).Conclusions: We found evidence to support an association between influenza vaccination and birth outcomes by trimester of receipt with data from an urban population in Nicaragua. The study had significant selection and recall biases. Prospective studies are needed to minimize these biases.

Impact of Timing of Influenza Vaccination in Pregnancy on Transplacental Antibody Transfer, Influenza Incidence, and Birth Outcomes: A Randomized Trial in Rural Nepal

“…An observational study in Australia found a 33% reduction in hospitalizations for respiratory illness among newborns of women vaccinated in the third trimester of pregnancy but no effect if vaccinated earlier in pregnancy [ 16 ]. An observational study in Nicaragua found reductions in preterm birth if vaccinated in the second and third trimesters of 13% and 34%, respectively, and a 20% and 36% reduction in LBW in infants of women vaccinated in the second and third trimester, respectively [ 17 ]. A retrospective analysis of 7 Vaccine Safety Datalink sites in the United States did not find any association between vaccine exposure and preterm and SGA overall, nor by trimester [ 18 ].…”

Knowledge, attitudes and practices about influenza vaccination among pregnant women and healthcare providers serving pregnant women in Managua, Nicaragua

“…We hypothesized that there were differences in the implementation of the recommendation of influenza vaccination among pregnant women based on HROC status [3]. Hypothesizing that 61% of pregnant women with HROC and 53% without HROC would receive influenza vaccination, and assuming that 57% of pregnant women in our study population would have HROC [3], we calculated a sample size of 1274 women using a formula to detect differences between proportions. Likewise, hypothesizing that 61% of pregnant women with HROC and 53% without HROC would receive influenza vaccination recommendation from a healthcare provider, we calculated a sample size of 600 healthcare providers.…”

“…The study noted that vaccinated pregnant women had more chronic diseases compared to unvaccinated ones (60% vs 53%, p < 0.01), suggesting that, in spite of the recent recommendation to vaccinate all pregnant women regardless of risk status, health workers continued to prioritize women with HROC [3]. In order to determine if healthcare providers were recommending influenza vaccination to all pregnant women regardless of HROC status, we conducted a follow-up survey of knowledge, attitudes and practices of health personnel and pregnant women in Managua.…”

Measurement of birth outcomes in analyses of the impact of maternal influenza vaccination

“…Some studies have further evaluated whether maternal influenza vaccination was associated with birth outcomes, including preterm birth and babies born small‐for‐gestational age (SGA). Though findings have been mixed, with some suggesting maternal vaccination reduced the risk of preterm delivery or was associated with SGA, while others have found no association . Influenza vaccination could, theoretically, prevent adverse birth outcomes by preventing potentially harmful inflammatory responses related to influenza virus infection.…”

“…Though findings have been mixed, with some suggesting maternal vaccination reduced the risk of preterm delivery or was associated with SGA, while others have found no association. [4][5][6][7][8][9][10][11][12] Influenza vaccination could, theoretically, prevent adverse birth outcomes by preventing potentially harmful inflammatory responses related to influenza virus infection. Though rarely seen in vaccine safety surveillance, detrimental effects of influenza vaccination, such as increased risk of miscarriage, preterm birth, or babies born small-for-gestational age, have also been investigated.…”