(P-024) Papillomavirus Vaccination and Guillain-barre Syndrome Among Girls: A Population-based Study in Spain

Background: Studies of the association of Guillain-Barré Syndrome (GBS) with papillomavirus vaccination (HPVv) have provided contradicting results, probably due to the low frequency of this disease.

Objectives: We aimed at estimating that risk relative to non-vaccination among girls, by using the Spanish Primary Care Database for Pharmacoepidemiological Research (BIFAP).

Methods: A cohort of girls aged 9-18 years during 2007-2016 free of GBS or HPVv was selected and followed up to GBS diagnosis. Follow-up time was divided by time-varying HPVv exposure and confounders. Crude Incidence rates (IR/1,000,000 person-years (py)) and adjusted Hazard Ratios (HR) of GBS were estimated anytime after vaccination compared to non-exposed periods. HRs were also estimated for the first 90 days after HPVv (risk-window) and thereafter.

Results: Out of 388,849 girls, 6 'confirmed' GBS cases occurred during non-exposure periods (IR of 5.83 per million person-years; 95%CI: 2.62-12.97) and 3 ‘confirmed’ cases anytime after vaccination (IR of 7.87; 95%CI: 2.54-24.39). The resulting adjusted HR anytime after vaccination was 0.45 (95%CI: 0.02-8.64). Those three cases occurred after the risk-window of 90 days, resulting in an HR of 1.57 (95%CI: 0.14-18.12) for post-exposure periods compared to non-exposure. Since zero cases occurred during the risk-window, no HR was produced for that period.

Conclusions: We did not find an association between human papillomavirus vaccination and the occurrence of Guillain-Barré syndrome. These results are in line with the range of GBS incidence previously reported for young people, supporting the potential of BIFAP for performing studies on GBS. However, the rarity of the disease could have precluded finding a case during the risk-window following vaccination.