Early effectiveness of the BNT162b2 KP.2 vaccine against COVID-19 in the US Veterans Affairs Healthcare System

Abstract

This test-negative case-control study within the US Veterans Affairs Healthcare System aims to estimate early vaccine effectiveness (VE) of the BNT162b2 KP.2 vaccine (2024–2025 formulation) compared to not receiving the KP.2 vaccine against COVID-19 outcomes. The study includes adult patients (age ≥18 years) with an acute respiratory infection (ARI) in hospital, emergency department and urgent care (ED/UC), or outpatient settings between September 5 and November 30, 2024. Separate multivariable logistic regression models compare the odds of receiving BNT162b2 KP.2 vaccine among SARS-CoV-2 positive cases and test-negative controls within each ARI outcome category, while adjusting for potentially confounding variables. Among 44,598 ARI episodes, VE is 68% (42–82%), 57% (46–65%), and 56% (36–69%) against COVID-19-associated hospitalizations, emergency department and urgent care visits, and outpatient visits, respectively. Uptake of updated COVID-19 vaccines is low (3.7%).