HPV vaccination and risk of chronic fatigue syndrome/myalgic encephalomyelitis: A nationwide register-based study from Norway.
Feiring, Berit, Laake, Ida, Bakken, Inger Johanne et al. · Vaccine · 2017 · DOI
Quick Summary
This study looked at whether the HPV vaccine (used to prevent cervical cancer) was linked to developing ME/CFS in Norwegian girls and boys between 2009 and 2014. Researchers tracked over 824,000 young people using national health records and found that girls who received the HPV vaccine were not at higher risk of developing ME/CFS compared to those who didn't receive it. The study did find that ME/CFS became slightly more common over time in both vaccinated and unvaccinated young people.
Why It Matters
This large-scale national study directly addresses a significant concern raised by some ME/CFS patients regarding vaccine safety. By using objective health records rather than self-report, the study provides robust evidence that can inform discussions between patients and clinicians about vaccine risks and benefits. The finding that prior illness predicts both CFS/ME and lower vaccination rates highlights the importance of controlling for baseline health status in vaccine safety studies.
Observed Findings
ME/CFS incidence increased similarly in both vaccinated and unvaccinated girls and boys from 2009-2014 (IRR≈1.15 per year).
Previous hospital contact was strongly predictive of CFS/ME diagnosis, with 7+ contacts showing 5.23-fold increased risk.
Girls with 7 or more prior hospital contacts were significantly less likely to be vaccinated (5.5% lower vaccination rate).
No increased CFS/ME risk was observed specifically in the 2 years following HPV vaccination.
Inferred Conclusions
HPV vaccination does not increase the risk of CFS/ME in this Norwegian population during the study period.
The apparent confounding between prior health problems, CFS/ME risk, and vaccine uptake suggests baseline health status is a critical variable in vaccine safety studies.
The unexplained rising trend in CFS/ME incidence among both vaccinated and unvaccinated youth suggests etiological factors other than HPV vaccination.
Remaining Questions
What explains the steady increase in CFS/ME incidence in both vaccinated and unvaccinated youth during 2009-2014?
Could the findings differ for other vaccines or in populations with different epidemiological patterns of ME/CFS?
What This Study Does Not Prove
This study does not prove that vaccines never trigger ME/CFS in any individual case, nor does it explain the biological mechanisms underlying ME/CFS. The study was limited to a specific vaccine (HPV), specific population (Norwegian youth), and specific time period (2009-2014), so findings may not generalize to other vaccines, populations, or older individuals. The observed increase in ME/CFS incidence over time remains unexplained by vaccination status.
Why does prior healthcare utilization so strongly predict ME/CFS diagnosis—does this reflect earlier detection, underlying predisposition, or iatrogenic factors?
Would similar findings be observed in countries with different HPV vaccination programs, age groups, or epidemiological patterns?