(P-022) Risk Factors for Thyroiditis Among Girls and Adolescents Scheduled to Human Papillomavirus Vaccination

Background: The frequency of autoimmune thyroiditis was studied after human papillomavirus vaccination.

Objectives: To find risk factors of thyroiditis among girls in the target age group for vaccination against human papillomavirus, as a preliminary step to study their potential link.

Methods: Cohort study including girls aged 9-18 years during 2007-2016 using the Spanish Primary Care Database For Pharmacoepidemiological Research (BIFAP). Adjusted Hazard Ratios of thyroiditis associated (reported as increased-fold (when HR≥2) or % (otherwise)) with selected clinical factors were estimated.

Results: Out of 388,411 girls included in the study cohort, 480 thyroiditis cases were identified (253 autoimmune (AITD); 227 unspecified aetiology). Factors significantly associated with an increased risk of thyroiditis were immunodeficiency disorders (7-fold), coeliac disease (4-fold), any autoimmune disease (4-fold), having reached menarche (89%), and higher healthcare use (one visit (32%) or ≥ 3 visits (82%) to the primary care). Previous hypothyroidism (2-fold) or hyperthyroidism (11-fold) were more frequent among cases. Girls aged 14-16 years were at a significantly decreased risk (34%-40%) of thyroiditis, while low weight (53%), chickenpox vaccination (48%), or iron supplements (39%) showed a non-significant increased risk.

Conclusions: Girls with (auto-)immune-related diseases and having reached menarche were at elevated risk of thyroiditis and hypo- or hyperthyroidism were more prevalent among them. Identification of these factors may provide information for early diagnosis and prevention of thyroiditis complications.