Question explored with the scientific record
Conversation so far
- 1 What benefit is the papaloma virus vaccine for young girls
- 2 What are the main risks or side effects, and how common are they?
Answered on this page ↓
What are the main risks or side effects, and how common are they?
The short version: most side effects are common, mild, and short-lived, but the most serious reported conditions are rare and the evidence on them is mixed.
The most common side effects are injection-site pain and mild systemic reactions. In clinical trials, about 84 in 100 vaccine recipients reported injection-site pain, compared with about 73 in 100 in the placebo group [4]. Systemic reactions like fever occurred in about 10 in 100 vaccinated people versus about 9 in 100 in the placebo group [4]. Serious adverse events were rare, under 0.1% in both groups [4].
Real-world surveillance data shows low overall reporting rates. In Alberta, adverse events were reported at a rate of about 37 per 100,000 doses [5]. In Slovenia, the rate was about 150 per 100,000 doses, with serious events at about 8 per 100,000 [2]. The most common reported events were allergic reactions, rash, and pain or swelling [5]. Syncope (fainting) was the most frequently reported event in US VAERS data, with about 8,351 reports out of 77,909 total [1].
| Event | Rate |
|---|---|
| Injection-site pain (trial) | ~84 in 100 vaccine recipients [4] |
| Systemic reactions (trial) | ~10 in 100 [4] |
| Serious adverse events (trial) | <0.1 in 100 [4] |
| All AEFI reports (Alberta) | ~37 per 100,000 doses [5] |
| All AEFI reports (Slovenia) | ~150 per 100,000 doses [2] |
| Serious AEFI reports (Slovenia) | ~8 per 100,000 doses [2] |
The more concerning signals come from passive reporting systems. POTS (a condition causing dizziness and rapid heartbeat on standing) showed the strongest statistical signal in VAERS, though the absolute number was small at 680 reports [1]. A large South Korean cohort study found no association between HPV vaccination and serious adverse events, including autoimmune conditions [3]. One migraine finding appeared in the cohort analysis but disappeared in the self-controlled analysis, suggesting it was not caused by the vaccine [3].
The key limitation: these rates come from passive surveillance systems that capture only a fraction of real events, and the trials were funded by the manufacturer [4]. The evidence does not include a long-term safety study comparing vaccinated to genuinely unvaccinated girls over decades.
My call: common side effects are frequent but mild and transient; serious harms appear rare but the surveillance systems used to measure them are weak. Confidence: moderate.
Sources used 5
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Adverse events following HPV vaccine reported to the Vaccine Adverse Event Reporting System
This pharmacovigilance study of 77,909 VAERS reports (2006-2024) finds syncope as the most frequently reported adverse event signal and POTS with the strongest disproportionality signal, with approximately 90% of adverse events occurring within 30 days of HPV vaccination.
DOI: 10.1371/journal.pone.0351652 -
Adverse events following school-based vaccination of girls with quadrivalent human papillomavirus vaccine in Slovenia, 2009 to 2013
During the first four school years of Slovenia's school-based qHPV vaccination of girls aged 11-14, the overall AEFI reporting rate was 149.5 per 100,000 doses distributed; serious AEFIs were rare, transient, and none caused permanent sequelae.
DOI: 10.2807/1560-7917.es.2016.21.14.30187 -
Association between human papillomavirus vaccination and serious adverse events in South Korean adolescent girls: nationwide cohort study
In a nationwide linked cohort of South Korean girls aged 11-14, HPV vaccination was not associated with serious adverse events in cohort or self-controlled risk interval analyses, except an inconsistent migraine finding attributed to age and menstrual factors.
DOI: 10.1136/bmj.m4931 -
The Quadrivalent Human Papillomavirus Vaccine: Potential Factors in Effectiveness
This narrative review reports that quadrivalent HPV vaccine is highly efficacious in HPV-naive females but less effective in general populations; early vaccination, durable protection, serotype interactions, and global HPV prevalence are key determinants of real-world impact.
DOI: 10.1016/j.jmwh.2007.12.015 -
Adverse events following HPV vaccination, Alberta 2006–2014
Adverse events following HPV vaccination in Alberta are rare (37.4 per 100,000 doses) and there is no evidence of VTE causally related to HPV vaccination; observed VTE cases occurred in individuals with other risk factors.
DOI: 10.1016/j.vaccine.2016.02.040