title: The Effect of Influenza Vaccination on Birth Outcomes in a Cohort of Pregnant Women in Lao PDR, 2014-2015.
abstract: 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.
  
  
  
  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.
  
  
  
  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).
  
  
  
  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.
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Sonja J
authors.initials: SJ
authors.lastname: Olsen
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Sara A
authors.initials: SA
authors.lastname: Mirza
authors.affiliation: Ministry of Health.
authors.forename: Phouvanh
authors.initials: P
authors.lastname: Vonglokham
authors.affiliation: Influenza Program, U.S. CDC-Lao People's Democratic Republic, American Embassy.
authors.forename: Viengphone
authors.initials: V
authors.lastname: Khanthamaly
authors.affiliation: Mother and Child Hospital.
authors.forename: Bounlap
authors.initials: B
authors.lastname: Chitry
authors.affiliation: Setthathirath Hospital, Vientiane.
authors.forename: Vathsana
authors.initials: V
authors.lastname: Pholsena
authors.affiliation: Luang Prabang Provincial Hospital, Lao People's Democratic Republic.
authors.forename: Visith
authors.initials: V
authors.lastname: Chitranonh
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, Atlanta, Georgia.
authors.forename: Saad B
authors.initials: SB
authors.lastname: Omer
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Ann
authors.initials: A
authors.lastname: Moen
authors.affiliation: Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Bresee
authors.affiliation: Influenza Program, U.S. CDC-Lao People's Democratic Republic, American Embassy The QED Group, American Embassy, Vientiane, Lao People's Democratic Republic.
authors.forename: Andrew
authors.initials: A
authors.lastname: Corwin
authors.affiliation: Ministry of Health.
authors.forename: Anonh
authors.initials: A
authors.lastname: Xeuatvongsa
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D007236:Infant, Small for Gestational Age; D007252:Influenza Vaccines / Q000008:administration & dosage*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D007812:Laos / Q000453:epidemiology; D008875:Middle Aged; D016017:Odds Ratio; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology / Q000517:prevention & control*; D014611:Vaccination; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
keywords: Laos; influenza vaccine; pregnant woman; preterm birth; small for gestational age