Updated 2025-2026 vaccination was linked to added protection in a CDC-funded analysis that became part of a broader debate over routine vaccine monitoring.
To evaluate the effectiveness of the 2025-2026 COVID-19 vaccine in providing short-term protection against medically attended COVID-19 among immunocompetent adults.
Approach:
Study Design: A test-negative case-control study using data from the VISION Network, assessing patients aged 18 years or older who sought care for COVID-19-like illness and underwent SARS-CoV-2 testing from September 3 to December 31, 2025.
Data Collection: Data were collected from 253 emergency department and urgent care sites and 179 hospitals across 7 US states.
Vaccine Effectiveness Estimation: Vaccine effectiveness was estimated by comparing the odds of vaccination among cases (positive SARS-CoV-2 test) versus controls (negative test), adjusting for demographic and geographic factors.
Key Findings:
Vaccine effectiveness was estimated at 50% against COVID-19-associated emergency department and urgent care encounters, reflecting short-term early-season protection.
Vaccine effectiveness was estimated at 55% against COVID-19-associated hospitalization, reflecting short-term early-season protection.
Among patients aged 65 years or older, effectiveness was 48% for ED/UC encounters and 53% for hospitalizations, reflecting short-term early-season protection.
Interpretation:
The estimates should be interpreted as the added benefit of a 2025-2026 dose in a population with existing immunity, rather than a comparison between vaccinated and immunologically naive patients, based on the study's findings.
Limitations:
Some patients may have sought care for reasons unrelated to COVID-19.
Vaccination status may have been misclassified.
Residual confounding from unmeasured factors may have influenced findings.
Low hospitalization rates and vaccination rates limited statistical power.
Findings may not be generalizable to all US patients.
Conclusion:
The study highlights the short-term effectiveness of the 2025-2026 COVID-19 vaccine in a population with high levels of immunity, based on the study's findings.
