Surveillance of Adverse Events After Seasonal Influenza Vaccination in Pregnant Women and Their Infants in the Vaccine Adverse Event Reporting System, July 2010–May 2016
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Routine immunization of pregnant women with seasonal inactivated influenza vaccines (IIVs) is recommended in all trimesters of pregnancy. A review of the Vaccine Adverse Event Reporting System (VAERS) during 1990–2009 did not find any unexpected patterns of pregnancy complications or fetal outcomes after administration of IIV or live attenuated influenza vaccines (LAIVs). During the 2009–2010 pandemic influenza A (H1N1) vaccination campaign, a study noted that the number of VAERS reports from pregnant women who received the H1N1 2009 inactivated monovalent vaccine (n = 288) increased compared with 1990–2009 seasonal IIV pregnancy reports (n = 148).
The objective of this study was to assess the safety of seasonal influenza vaccines in pregnant women and their infants whose reports were submitted to VAERS during 2010–2016.
We searched VAERS for US reports of adverse events (AEs) in pregnant women who received IIV or LAIV from 1 July 2010 through 6 May 2016. Clinicians reviewed reports and available medical records and assigned a primary clinical category for each report. Reports were coded as serious based on the Code of Federal Regulations.
We identified 671 reports after seasonal influenza vaccines administered to pregnant women: 544 after IIV and 127 after LAIV. Serious events occurred among 61 (11.2%) reports following IIV and one (0.8%) report following LAIV. No deaths were reported. Among reports with trimester information (n = 296), IIV was administered during the first trimester in 116 (39.2%). Among IIV reports, the most frequent pregnancy-specific AE was spontaneous abortion in 62 (11.4%) reports, followed by stillbirth in ten (1.8%) and preterm delivery in six (1.1%). The most common non-pregnancy-specific AEs were injection-site reactions (55 [10.1%]). Neonatal or infant outcomes were reported in 22 (4.0%) reports, seven of which had major birth defects of different types and no neonatal deaths.
As in 2009–2010, no new or unexpected patterns in maternal or fetal outcomes were observed during 2010–2016.
KeywordsInfluenza Influenza Vaccine Preterm Delivery H1N1 Pandemic Major Birth Defect
We thank the CDC’s Immunization Safety Office staff, whose work allowed this activity to be conducted. We also thank staff from cSRA, Inc. for their work on this project.
Compliance with Ethical Standards
No external or internal sources of funding were used for this study.
Conflict of interest
Pedro Moro, Jane Baumblatt, Paige Lewis, Janet Cragan, Naomi Tepper, and Maria Cano have no conflicts of interest that are directly relevant to the content of this study. Part of this research was presented during the 31st International Conference on Pharmacoepidemiology & Therapeutic Risk Management (ICPE) that was held from 22 to 26 August 2015 in Boston, MA, USA.
Because VAERS is a routine surveillance program that does not meet the definition of research, it is not subject to Institutional Review Board review and informed consent requirements.
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