TY - JOUR T1 - Incidence and Risk Factors of COVID-19 Vaccine Breakthrough Infections: A Prospective Cohort Study in Belgium. JF - Viruses Y1 - 2022 A1 - Veerle Stouten A1 - Pierre Hubin A1 - Freek Haarhuis A1 - Joris Van Loenhout A1 - Matthieu Billuart A1 - Ruben Brondeel A1 - Toon Braeye A1 - Herman Van Oyen A1 - Chloé Wyndham-Thomas A1 - Lucy Catteau KW - Ad26COVS1 KW - Adult KW - Belgium KW - BNT162 Vaccine KW - COVID-19 KW - COVID-19 Vaccines KW - Humans KW - incidence KW - Prospective Studies KW - Risk Factors KW - SARS-CoV-2 AB -

The objective of this study was to investigate the incidence and risk factors associated with COVID-19 vaccine breakthrough infections. We included all persons ≥18 years that had been fully vaccinated against COVID-19 for ≥14 days, between 1 February 2021 and 5 December 2021, in Belgium. The incidence of breakthrough infections (laboratory confirmed SARS-CoV-2-infections) was determined. Factors associated with breakthrough infections were analyzed using COX proportional hazard models. Among 8,062,600 fully vaccinated adults, we identified 373,070 breakthrough infections with an incidence of 11.2 (95%CI 11.2-11.3)/100 person years. Vaccination with Ad26.COV2.S (HR1.54, 95%CI 1.52-1.56) or ChAdOx1 (HR1.68, 95%CI 1.66-1.69) was associated with a higher risk of a breakthrough infection compared to BNT162b2, while mRNA-1273 was associated with a lower risk (HR0.68, 95%CI 0.67-0.69). A prior COVID-19-infection was protective against a breakthrough infection (HR0.23, 95%CI 0.23-0.24), as was an mRNA booster (HR0.44, 95%CI 0.43-0.45). During a breakthrough infection, those who had a prior COVID-19 infection were less likely to have COVID-19 symptoms of almost all types than naïve persons. We identified risk factors associated with breakthrough infections, such as vaccination with adenoviral-vector vaccines, which could help inform future decisions on booster vaccination strategies. A prior COVID-19 infection lowered the risk of breakthrough infections and of having symptoms, highlighting the protective effect of hybrid immunity.

VL - 14 CP - 4 M3 - 10.3390/v14040802 ER -