Epidemiological aspects of headache after different types of COVID-19 vaccines: An online survey

Coronavirus disease 2019 (COVID-19) vaccine-related side effects are a key concern with the emergence of various types of vaccines in the market. We aimed to assess the frequency and characteristics of headache following different types of COVID-19 vaccines.

Fully vaccinated people were recruited by a convenience sample through an online survey from September 1 to December 1, 2021. Detailed analysis of headache following vaccination was investigated. Participants with a history of pre-existing headaches were telephone interviewed by a neurologist to ascertain the type of headache.

A total of 1372 participants participated (mean age 32.9 ± 11.1). The highest frequency of headache was reported with the adenoviral vector type (302/563, 53.6%), followed by mRNA vaccines (129/269, 48%) and then the inactivated type (188/540, 34.8%). Recipients of the adenoviral vector type had a significantly longer latency between vaccination and the headache onset (median 8 h [5:12]) than recipients of the inactivated type (median 4 h [2:8], p < 0.001). Headache intensity was significantly higher with the adenoviral vector type (median 6 [5:8]) than with the inactivated type (median 5 [4:7], p < 0.001). Adenoviral vector vaccines would increase the likelihood of headache by 2.38 times more than inactivated vaccines (odds ratio [OR] 2.38, 95% confidence interval [CI] 1.83-3.04, p < 0.001). Female sex and thyroid disease were significantly associated with headache related to COVID-19 vaccines (OR 1.52, 95% CI 1.16-1.99; OR 3.97, 95% CI 1.55-10.2, respectively).

Recipients of the COVID-19 vaccine should be counseled that they may experience headaches, especially after the adenoviral vector type. However, the intensity of such headache is mild to moderate and can resolve within a few days. Based on the current study design and the potential recall bias, these results may not be generalizable and should be preliminary.