OBJECTIVES : The Advisory Committee on Immunization Practice recommends the use of influenza and tetanus diphtheria and pertussis (Tdap) vaccines during pregnancy since 1997 and 2011, respectively. This study examined the characteristics and trends of adverse events (AE) of pregnant women reported to the US Vaccine Adverse Events Reporting System (VAERS) in the period January 1, 2014-September 14, 2018.

METHODS : Reports from VAERS were searched from January 1, 2014 to September 14, 2018. Reports of pregnant women were identified by text string search for “preg” in symptom description and the Medical Dictionary for Regulatory Activities (MedDRA) terms: “pregnancy”, “puerperium”, and “perinatal conditions” and “drug exposure during pregnancy.” AEs were characterized into groups based on AE severity. Descriptive statistics including reporting rates by vaccine type, severity status and most common AE in pregnant women were conducted using IBM SPSS 25.

RESULTS : VAERS listed a total of 249,631 reports for the period of analysis. Of those reports, 193,498 (77.5%) mentioned a vaccine AE. There were 1,486 (0.8%) reports for pregnant women with an AE. The mean ± standard deviation of the age of pregnant women was 26.3±7.9 years. There were 173 pregnancy-related serious AE representing 16.8% of all events of pregnant women. Pregnancy-related serious AE included 92 (6.2%) abortions, 65 (4.4%) miscarriages, 13 (0.9%) stillbirths, and 3 (0.2%) birth defects. The outcomes of the serious AEs included 249 (16.8%) emergency room visits, 78 (5.2%) hospitalizations, 40 (2.7%) disability events, and 16 (1.1%) life-threatening events. Reporting rates of AEs in pregnant women as a percent of all VAERS reports decreased from 0.98% in 2014 to 0.65% in 2018.

CONCLUSIONS : VAERS reports do not determine causality between vaccine AE and pregnancy. A small percentage of VAERS reports included AEs in pregnant women. VAERS reporting rates including pregnant women decreased in the period of analysis.