Updated COVID-19 BNT162b2 KP.2 Vaccine Protective Against Severe Outcomes
The BNT162b2 KP.2 COVID-19 vaccine had protective effects against emergency department (ED) or urgent care (UC) encounters and hospital admissions, according to study results published in Open Forum Infectious Diseases.
In the summer of 2024, the United States Food and Drug Administration authorized an update to the mRNA COVID-19 vaccine to target the KP.2 sublineage.
To assess the vaccine effectiveness (VE) and durability of the BNT162b2 KP.2 vaccine, investigators from Kaiser Permanente Southern California conducted a test-negative case-control study. The analysis included adults (N=65,584) who presented at the ED or UC (n=54,024) or were admitted to the hospital (n=11,560) with acute respiratory infection (ARI) and underwent SARS-CoV-2 testing by polymerase chain reaction between September 2024 and April 2025. Patients were evaluated for COVID-19 positivity on the basis of whether they received the BNT162b2 KP.2 vaccine. Multivariable logistic regression was employed for statistical analysis.
[R]eceipt of BNT162b2 KP.2 COVID-19 vaccine provides durable protection against serious COVID-19 outcomes regardless of prior vaccination history and among older age groups, supporting deliberations of updated COVID-19 vaccine.
Among vaccinated and unvaccinated patients, median ages were 70 (IQR, 54-80) and 50 (IQR, 34-68) years, respectively. The overall SARS-CoV-2 positivity rate was 5.1%. Rates of BNT162b2 KP.2 vaccination were lower among case patients (12.3%) compared with control patients (16.0%).
The median time from BNT162b2 KP.2 receipt to ARI was 94 (IQR, 58-133) days, and the time from pre-BNT162b2 KP.2 COVID-19 vaccine formulation receipt to ARI was 1091 (IQR, 840-1223) days.
The adjusted VE of BNT162b2 KP.2 against COVID-19-related hospitalization was 49% (95% CI, 30-63) within 3 months of vaccination and declined to 35% (95% CI, 8-54) at 3 months or longer. Additionally, adjusted VE against ED or UC encounters was 45% (95% CI, 35-54) within 3 months and 26% (95% CI, 12-38) thereafter. VE outcomes were similar across prior vaccination receipt groups and when stratified by age.
When individuals who tested positive for influenza were excluded from the analyses, VE estimates changed by 2% or less.
Study limitations include potential study design-related underestimation of VE and residual confounding.
The investigators concluded, “[R]eceipt of BNT162b2 KP.2 COVID-19 vaccine provides durable protection against serious COVID-19 outcomes regardless of prior vaccination history and among older age groups, supporting deliberations of updated COVID-19 vaccine.”
Disclosure: This research was supported by Pfizer, Inc. Please see the original reference for a full list of disclosures.
