General Obstetrics and Gynecology: ObstetricsSafety of influenza vaccination during pregnancy
Section snippets
Material and methods
We performed a retrospective electronic database search to include 5 influenza seasons from July 1, 1998, to June 30, 2003, at a large multispecialty clinic in Houston, Texas. The study protocol was reviewed and approved by the Institutional Review Board of Baylor College of Medicine and the National Institutes of Health and the Research and Education Committee at Kelsey-Seybold Clinic (KSC).
A data manager at the Kelsey Research Foundation identified the study population through the KSC
Inclusion and exclusion criteria
Women were included in the study sample if they had received inactivated influenza vaccine within 6 months before delivery of an uncomplicated singleton pregnancy and were otherwise healthy, had at least 1 prenatal care visit at KSC, and their offspring had at least 1 clinic visit at KSC in their first year of life. These criteria were selected to improve the probability of having maternal and infant safety data available in the database. Women with pregnancies that were complicated by multiple
Study outcomes
Influenza immunization rates were calculated for the study population. The demographic characteristics and outcomes of pregnancy were compared between the cohort of healthy vaccinated women and the matched control group. A pseudovaccination date was assigned to each member of the control group. The date was selected to be the same number of days before delivery as the real vaccination date for a matching vaccinated woman. Safety of influenza vaccination was assessed by the identification of all
Statistical analysis
Outcomes were compared between the 2 study groups, with maternal vaccination as the independent variable. Continuous values (such as age, gestational age, and interval between vaccination and delivery) were analyzed with t-test for comparison of the means. Nominal values were compared among the groups with chi-squared test or Fisher exact test. Differences were considered statistically significant if the probability value was <.05, with 95% CI.
Results
The database search identified 7183 mother-infant pairs who met the inclusion criteria. Only 252 of 7183 pregnant women (3.5%) received influenza vaccine. Among 6029 women with medical insurance (not Medicaid), 245 women (4.1%) received influenza vaccine, and only 7 of 1154 women (0.6%) with Medicaid or no insurance were vaccinated (P < .001 vs uninsured; odds ratio, 6.9; 95% CI, 3.2-16). The rate of influenza vaccination in women with chronic underlying conditions was 3.7% (25/665 women),
Comment
The impact of influenza infection during pregnancy has been documented over several decades. The need to protect women in the second and third trimester of gestation originated from the observation of the high mortality rate in this population during influenza pandemics in the first one half of the 20th century. Epidemiologic studies during interpandemic periods have demonstrated that pregnancy itself is a condition that places otherwise healthy women at risk for severe influenza and
References (14)
- et al.
Deaths from Asian influenza associated with pregnancy
Am J Obstet Gynecol
(1959) - et al.
Maternal morbidity and perinatal outcomes among pregnant women with respiratory hospitalizations during influenza season
Am J Obstet Gynecol
(2003) Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices [ACIP]
MMRW Morb Mortal Wkly Rep
(2004)- et al.
Influenza virus
- et al.
Impact of influenza on acute cardiopulmonary hospitalizations in pregnant women
Am J Epidemiol
(1998) Influenza occurring in pregnant women: a statistical study of thirteen hundred and fifty cases
JAMA
(1919)- Centers for Disease Control and Prevention. Guidelines for vaccinating pregnant women. Updated October 2003. Available...
Cited by (223)
Maternal Vaccination and Vaccine Hesitancy
2023, Pediatric Clinics of North AmericaSafety of influenza vaccination on adverse birth outcomes among pregnant women: A prospective cohort study in Japan
2020, International Journal of Infectious Diseases
Supported by National Institutes of Health Grant no. N01-AI-65316.
Presented at the 1st International Conference on Influenza Vaccines for The World, Lisbon, Portugal, May 24-26, 2004.