Association between human papillomavirus vaccination and serious adverse events in South Korean adolescent girls: nationwide cohort study

This study (n=441,399 girls aged 11-14; 382,020 vaccinated against HPV) found no association between HPV vaccination and the occurrence of 33 serious adverse events within one year of vaccination; including a subgroup analysis according to type (bivalent; quadrivalent).

SPS commentary:

Although in cohort analyses there was an increased risk of migraine, the lower limit of the 95% CI was close to 1 (RR 1.11, 1.02 to 1.22), and the results of the self-controlled risk interval analysis showed no significant increase in risk (RR 0.67, 95% CI 0.58 to 0.78). The latter analysis included girls with a history of both HPV vaccination and predefined serious adverse events; this means that time invariant confounders (sex, region of residence, type of health insurance, income level, lifestyle) are self-adjusted, and the design is less subject to unmeasured confounders.

British Medical Journal