Abstract
BackgroundThailand recommends influenza vaccination among pregnant women. We conducted a cohort study to determine if the prevalence of adverse events following immunization (AEFIs) with influenza vaccine among Thai pregnant women was similar to that often cited among healthy adults.MethodsWomen who were ≥17 gestational weeks and ≥18 years of age were recruited. Demographic and health history data were collected using structured questionnaires. Women were provided with symptom diary, ruler to measure local reaction(s), and thermometer to measure body temperature. AEFIs were defined as any new symptom/abnormality occurring within four weeks after vaccination. The diaries were abstracted for frequency, duration, and level of discomfort/inconvenience of the AEFIs. Serious adverse events (SAEs) and the likelihood of AEFIs being associated with vaccination were determined using standard definitions.ResultsAmong 305 women enrolled between July–November 2015, median age was 29 years. Of these, 223 (73%) were in their third trimester, 271 (89%) had completed secondary school or higher, and 20 (7%) reported ≥1 pre-existing conditions. AEFIs were reported in 134 women (44%; 95% confidence interval [CI] 38–50%). Soreness at the injection site (74, 24%; CI 19–29%), general weakness (50, 16%; CI 12–21%), muscle ache (49, 16%; CI 12–21%), and headache (45, 15%; CI 1–19%) were most common. Of those with AEFIs, 120 (89%) reported symptom/abnormality occurred on day 0 or day 1 following vaccination. Ten women (7%) reported the AEFIs affected daily activities. The AEFIs generally spontaneously resolved within 24 h of onset. There were two vaccine-unrelated SAEs. Of 294 women with complete follow-up, 279 (95%) had term deliveries, 12 (4%) had preterm deliveries, and 3 (1%) had miscarriage or stillbirth.ConclusionIn our cohort, AEFIs with influenza vaccine occurred with similar frequency to those reported among healthy adults in other studies, and were generally mild and self-limited. No influenza vaccine-associated SAEs were identified.
Highlights
Thailand recommends influenza vaccination among pregnant women
We used a cohort study design to enroll women at the time of influenza vaccination (Influvac®, Abbott Biologicals B.V., The Netherlands) [20] and follow them through the first four weeks post-vaccination to measure the frequency of Adverse event following immunization (AEFI)
Between July and November 2015, all 378 women with influenza vaccination prescription were screened for enrollment, of whom 308 (81%) were eligible for inclusion
Summary
Thailand recommends influenza vaccination among pregnant women. In 2009, the Thailand Ministry of Public Health (MOPH) issued a recommendation that pregnant women should receive influenza vaccine after the third month of pregnancy [2]. A recent analysis by Owusu et al revealed very low uptake of influenza vaccine in Thai pregnant women: 1.1% in 2010, 0.7% in 2011, and 0.9% in 2012 [16]. These data indicate that the national policy on influenza vaccination in pregnant women is not widely implemented. The lower vaccination rates in pregnant women could be due to operational issues, but concerns by both pregnant women and their clinicians about the safety of the influenza vaccine during pregnancy may limit vaccination rates [6]
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