Effectiveness of the XBB.1.5 updated COVID-19 vaccine against hospitalisation: a nation-wide cohort study in Denmark, October 2023

Abstract

The XBB.1.5 updated COVID-19 mRNA vaccines currently form part of the national immunisation programmes in many countries including Denmark. Here we present a cohort analysis with national electronic health registry data estimating the protection offered by the updated vaccines against hospital admission in October 2023. After adjustment in a Cox proportional hazards regression model for sex, age, residency region and comorbidities, those who had received the seasonal COVID-19 vaccine were much less likely to have been hospitalised for COVID-19 compared with those who had not received the vaccine (HR=0.247, 95% CI 0.157, 0.389), although a negative control outcome analysis indicated that the unvaccinated group had somewhat poorer health in general. Overall, our early results indicate a high level of protection from the XBB.1.5 vaccines.

Note:

Funding Information: There was no separate funding source for this study. All authors are employed by Statens Serum Institut, Copenhagen, Denmark.

Conflict of Interests: The authors have no competing interest to declare.

Keywords: Vaccine effectiveness, SARS-CoV-2, COVID-19, negative control outcome, cohort analysis