Background: Vaccination has been suggested to be involved in the aetiology of chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). HPV vaccine was introduced in the Norwegian Childhood Immunisation Programme and offered 12year old girls from 2009. We studied the association between HPV vaccination and risk of CFS/ME and also assessed medical history in relation to both risk of CFS/ME and HPV vaccine uptake.
Methods: Individual data from national registries, including the Norwegian Population Registry, the Norwegian Patient Registry and the Norwegian Immunisation Registry were linked using the unique personal identification number. Yearly incidence rates of CFS/ME for 2009-2014 were calculated among the 824,133 boys and girls, aged 10-17 living in Norway during these 6years. A total of 176,453 girls born 1997-2002 were eligible for HPV vaccination and included in further analyses. Hazard ratios (HRs) of CFS/ME were estimated using Cox regression. Risk differences (RDs) of vaccine uptake were estimated with binomial regression.
Results: A similar yearly increase in incidence rate of CFS/ME was observed among girls and boys, IRR=1.15 (95% confidence interval (CI) 1.10-1.19) and 1.15 (95% CI 1.09-1.22), respectively. HPV vaccination was not associated with CFS/ME, HR=0.86 (95% CI 0.69-1.08) for the entire follow-up period and 0.96 (95% CI 0.64-1.43) for the first two years after vaccination. The risk of CFS/ME increased with increasing number of previous hospital contacts, HR=5.23 (95% CI 3.66-7.49) for 7 or more contacts as compared to no contacts. Girls with 7 or more hospital contacts were less likely to be vaccinated than girls with no previous hospital contacts, RD=-5.5% (95% CI -6.7% to -4.2%).
Conclusions: No indication of increased risk of CFS/ME following HPV vaccination was observed among girls in the first 6 birth cohorts offered HPV vaccine through the national immunisation programme in Norway.
Keywords: Chronic fatigue syndrome; Human papillomavirus vaccine; Medical history; Myalgic encephalomyelitis; Vaccine safety; Vaccine uptake.
Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.