Research Summary

Systematic Review Finds COVID-19 Vaccines Reduce Severe Outcomes

Anthony Calabro, MA

Key Highlights

  • Updated COVID-19 vaccines were associated with approximately 53% to 54% effectiveness against hospitalization in recent studies of adults.
  • Vaccination during pregnancy was associated with protection for pregnant individuals and infants after birth.
  • Vaccination was associated with lower risks of pediatric emergency care and critical illness among immunocompromised adults.
  • The review identified no new COVID-19 vaccine safety signals.

COVID-19 vaccines remained associated with lower risks of hospitalization and other severe outcomes across age and risk groups, with no new safety concerns identified, according to a systematic review published in JAMA. The review evaluated evidence relevant to COVID-19 vaccination for the 2026-2027 respiratory season.

Researchers searched the Cochrane Central Register of Controlled Trials, PubMed/MEDLINE, Embase, and Scopus for studies published from August 1, 2025, through June 29, 2026. Eligible studies evaluated the effectiveness, efficacy, or safety of a US-licensed COVID-19 vaccine or examined SARS-CoV-2 epidemiology in the United States.

Of 11,829 identified records, 155 publications met the inclusion criteria. These included 15 randomized clinical trials, 84 observational studies with comparator groups, 38 product safety studies without comparator groups, and 18 descriptive studies of COVID-19 disease burden.

Study Findings

During the 2025-2026 season, updated vaccines demonstrated 53.0% effectiveness against COVID-19–related hospitalization among adults aged ≥65 years (95% CI, 37.0%-65.0%). A study from the 2024-2025 season reported 54.0% effectiveness against hospitalization among adults aged 18 to 64 years (95% CI, 1.0%-78.0%).

Vaccination during pregnancy was associated with 58.0% effectiveness against COVID-19–related emergency department or urgent care encounters among pregnant individuals (95% CI, 24.0%-77.0%). Maternal vaccination was also associated with 50.0% to 54.0% effectiveness against COVID-19–related hospital contacts among infants during their first 2 months of life, depending on the trimester of vaccination.

Among children aged 9 months to 4 years, updated vaccines demonstrated 76.0% effectiveness against COVID-19–associated emergency department or urgent care encounters (95% CI, 58.0%-87.0%). Effectiveness against critical COVID-19 illness among adults receiving hemodialysis ranged from 32.0% to 53.0%, depending on additional immunocompromising conditions and time since vaccination.

The safety profiles were consistent with previous reviews, and no new safety signals were identified. Studies conducted exclusively under the updated primary-series dosing intervals did not report an increased risk of myocarditis or pericarditis, although the review authors noted that eligible evidence specific to the revised schedule was limited.

Clinical Implications

According to the authors, the evidence reinforces the importance of vaccination for preventing serious COVID-19 outcomes, particularly among older adults, infants, children, pregnant individuals, and people with underlying medical conditions. They also emphasized the need for continued evidence evaluation to inform current vaccination policies as SARS-CoV-2 variants and population immunity change.

The review covered a defined publication period and did not represent the totality of COVID-19 vaccine evidence. The authors also noted variation in study quality and cautioned that studies without appropriate comparator groups could not support causal conclusions.

Expert Commentary

“These findings reinforce the importance of vaccination in preventing serious COVID-19 outcomes,” the researchers concluded.

Reference
Lipson RA, Senerth E, Watson MA, et al. COVID-19 vaccine effectiveness and safety for the 2026-2027 respiratory season. JAMA. Published online September 2, 2026. doi:10.1001/jama.2026.1819