On Feb. 4, 2026, the U.S. Centers for Disease Control and Prevention (CDC) reported the 2024-25 COVID-19 vaccine was an estimated 40% effective against hospital admission and 79% effective against invasive mechanical ventilation (IMV) or death.

In this case-control study of 1888 adults with COVID-19 and 6605 adults without COVID-19, the estimated VE was similar for KP.3.1.1 and XEC lineages, as well as for spike protein mutations potentially associated with immune evasion (S31 deletion, T22N and F59S substitutions).

The CDC researchers cautiously concluded this multicenter, case-control analysis of VE, 2024-2025 COVID-19 vaccines may have provided protection against hospitalizations and severe in-hospital outcomes as multiple JN.1 descendant lineages circulated. Monitoring COVID-19 VE, including stratifying by SARS-CoV-2 lineage and spike protein mutations, remains important to guide COVID-19 vaccine composition and recommendations. The study results were published in JAMA Network Open.