Sonja J Olsen1, Sara A Mirza1, Phouvanh Vonglokham2, Viengphone Khanthamaly3, Bounlap Chitry4, Vathsana Pholsena5, Visith Chitranonh6, Saad B Omer7, Ann Moen1, Joseph S Bresee1, Andrew Corwin8, Anonh Xeuatvongsa2. 1. Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia. 2. Ministry of Health. 3. Influenza Program, U.S. CDC-Lao People's Democratic Republic, American Embassy. 4. Mother and Child Hospital. 5. Setthathirath Hospital, Vientiane. 6. Luang Prabang Provincial Hospital, Lao People's Democratic Republic. 7. Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia. 8. Influenza Program, U.S. CDC-Lao People's Democratic Republic, American Embassy The QED Group, American Embassy, Vientiane, Lao People's Democratic Republic.
Abstract
BACKGROUND: Some studies suggest that maternal influenza vaccination can improve birth outcomes. However, there are limited data from tropical settings, particularly Southeast Asia. We conducted an observational study in Laos to assess the effect of influenza vaccination in pregnant women on birth outcomes. METHODS: We consented and enrolled a cohort of pregnant woman who delivered babies at 3 hospitals during April 2014-February 2015. We collected demographic and clinical information on mother and child. Influenza vaccination status was ascertained by vaccine card. Primary outcomes were the proportion of live births born small for gestational age (SGA) or preterm and mean birth weight. Multivariate models controlled for differences between vaccinated and unvaccinated women and influenza virus circulation. RESULTS: We enrolled 5103 women (2172 [43%] were vaccinated). Among the 4854 who had a live birth, vaccinated women were statistically significantly less likely than unvaccinated women to have an infant born preterm during the period of high influenza virus circulation (risk ratio [RR] = 0.56, 95% confidence interval [CI], .45-.70), and the effect remained after adjusting for covariates (adjusted RR, 0.69; 95% CI, .55-.87). There was no effect of vaccine on mean birth weight. Vaccinated mothers had a statistically significant elevated risk of having an infant born SGA (adjusted RR, 1.25; 95% CI, 1.11–1.41). CONCLUSIONS: In this observational study, we found indirect evidence of influenza vaccine safety during pregnancy, and women who received vaccine had a reduced risk of delivering a preterm infant during times of high influenza virus circulation. Vaccination may prevent 1 in 5 preterm births that occur during periods of high influenza circulation. Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.
BACKGROUND: Some studies suggest that maternal influenza vaccination can improve birth outcomes. However, there are limited data from tropical settings, particularly Southeast Asia. We conducted an observational study in Laos to assess the effect of influenza vaccination in pregnant women on birth outcomes. METHODS: We consented and enrolled a cohort of pregnant woman who delivered babies at 3 hospitals during April 2014-February 2015. We collected demographic and clinical information on mother and child. Influenza vaccination status was ascertained by vaccine card. Primary outcomes were the proportion of live births born small for gestational age (SGA) or preterm and mean birth weight. Multivariate models controlled for differences between vaccinated and unvaccinated women and influenza virus circulation. RESULTS: We enrolled 5103 women (2172 [43%] were vaccinated). Among the 4854 who had a live birth, vaccinated women were statistically significantly less likely than unvaccinated women to have an infant born preterm during the period of high influenza virus circulation (risk ratio [RR] = 0.56, 95% confidence interval [CI], .45-.70), and the effect remained after adjusting for covariates (adjusted RR, 0.69; 95% CI, .55-.87). There was no effect of vaccine on mean birth weight. Vaccinated mothers had a statistically significant elevated risk of having an infant born SGA (adjusted RR, 1.25; 95% CI, 1.11–1.41). CONCLUSIONS: In this observational study, we found indirect evidence of influenza vaccine safety during pregnancy, and women who received vaccine had a reduced risk of delivering a preterm infant during times of high influenza virus circulation. Vaccination may prevent 1 in 5 preterm births that occur during periods of high influenza circulation. Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.
Entities:
Keywords:
Laos; influenza vaccine; pregnant woman; preterm birth; small for gestational age
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