General Practitioner Attendance in Proximity to HPV Vaccination: A Nationwide, Register-Based, Matched Case–Control Study

Aim: This study aimed to describe and compare general practitioner (GP) attendance patterns in the years surrounding HPV-vaccination among cases suspected to experience adverse events and their matched controls in order to determine if a potential larger change in GP attendance among cases was observed in temporal relation to vaccination. Methods: Register-based, matched case–control study. Cases were defined as women referred to specialized hospital settings (HPV-centers) for suspected adverse event between June 1st 2015 and December 31st 2015 (n=1458). Information on referral was obtained from the HPV-centers directly. Each case was matched with five controls on age at vaccination, region, time of first vaccine registration and total number of doses, resulting in a total study population of 8670 girls and women. Negative binomial regression analyses were used (i) to estimate mean yearly GP contacts among cases and controls, and (ii) to further investigate the relative difference in change in GP attendance following vaccination between cases and controls. Results: Overall, cases displayed higher GP attendance than controls from five years before vaccination up until five years after. Compared to controls, cases increased their GP attendance more in the years following HPV vaccination, corresponding to a 40% increase in the incidence rate ratios (IRR) from before to after vaccination (ratio-IRR = 1.40 [1.36; 1.44]). The change occurred in close proximity to vaccination, and the pattern was the same independently of the year of vaccination. However, for the later vaccination years cases displayed an additional increase in their GP attendance around time of extensive media attention. Conclusion: Girls and women being referred for suspected adverse events after HPVvaccination changed their GP attendance pattern in close proximity to their first HPVvaccination and not solely in temporal linkage to the onset of public debate.