Post‐vaccination headache reporting: Trends according to the Vaccine Adverse Events Reporting System

Abstract

AbstractObjectiveTo assess the characteristics and associated disability of headache as an adverse event following vaccination.BackgroundAccording to clinical trials and post‐licensure surveillance, headache is a common symptom of vaccines, yet systematic investigations of post‐licensure reports of this adverse event are lacking.MethodsThis was a retrospective database analysis study. We searched the Vaccine Adverse Events Reporting System (VAERS) database completed from July 1990 to June 2020 (a 30‐year period prior to the start of COVID‐19 pandemic) to identify reports of headache. We evaluated epidemiological features, including event characteristics, patient demographics, and vaccine type.ResultsIn those aged 3 years or older, headache was the fifth most reported adverse symptom, present in 8.1% (43,218/536,120) of all reports. Of headache reports, 96.3% (41,635/43,218) included the code “headache” not further specified. Migraine was coded in 1973 cases, although almost one‐third (12,467/41,808; 29.8%) of headache reports without a migraine code mention nausea or vomiting. The onset of symptoms was within 1 day of vaccination in over two‐thirds of cases. The majority of reports were classified as not serious; about one‐third involved emergency room or office visits. Of the 43,218 total headache reports, only a minority involved hospitalizations (2624; 6.1%) or permanent disability (1091; 2.5%), females accounted for 68.9% (29,771) and males for 29.5% (12,725), patients aged 6 to 59 years represented 67.3% (29,112), and over one‐third of cases were reported after herpes zoster (8665; 20.1%) and influenza (6748; 15.6%) vaccinations.ConclusionIn a national surveillance system, headache was a commonly reported post‐vaccination adverse event; a small subset of reports was considered serious. The development of standardized vaccine‐related case definitions could be useful for better evaluating headache as an adverse event during vaccine development, and may reduce vaccine hesitancy especially in headache‐prone individuals.