Oral contraceptive usage among healthcare workers and its impact on COVID-19 booster vaccination immunogenicity

Oral contraceptives (OCs) can substantially modulate immune responses; however, their impact on vaccine immunogenicity remains poorly understood. This study investigated OC use patterns and their determinants among healthcare workers (HCWs), and the effects of OCs on humoral and T-cell-mediated immune responses following COVID-19 booster vaccination. From 29 September 2021 to 31 December 2023, 1061 female HCWs aged 18-50 years were enrolled in the CoVacSer study. OC users were compared to non-users. Blood samples combined with a questionnaire were collected before and after third and fourth COVID-19 vaccination including follow-ups. Anti-SARS-CoV-2-Spike IgG levels were measured using SERION ELISA agile SARS-CoV-2 IgG, T-cellular immune response using Oxford Immunotec T-SPOT®.COVID. A linear mixed and a generalised linear model were used to assess the influence of OC on post-vaccination immune response. At study inclusion, 21.7% (230/1061) reported OC use. Younger age, being a physician, and higher BMI were significantly associated with OC. Linear mixed and generalised linear regression models revealed no significant association between reported OC use and humoral and T-cellular immune response before and after COVID-19 vaccination. Although OC are known to modulate immune responses, this study found no statistically significant association between self-reported OC use and humoral or cellular immunogenicity following COVID-19 vaccination. This is among the first studies to address this in the context of COVID-19 booster vaccination. Our findings suggest that in women using OC no specific adjustments to COVID-19 vaccination strategies are required considering OC use. Continued investigation of potential interactions between OC and vaccine- or infection-induced immunity remain warranted.