Are currently available COVID-19 (Coronavirus Disease 2019) vaccines effective against recent strains of SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2)?

From the Guidelines

The currently available COVID-19 vaccines, specifically the 2024-2025 formulations, are effective against recent strains, including the Omicron JN.1 lineage strains, and provide strong protection against severe illness, hospitalization, and death. According to the Advisory Committee on Immunization Practices (ACIP) recommendations, as of 2024, COVID-19 vaccination provides additional protection against severe COVID-19–associated illness and death 1. The 2024-2025 COVID-19 vaccines, such as those from Moderna and Pfizer-BioNTech (based on the KP.2 strain) and Novavax (based on the JN.1 strain), have been approved or authorized for use in persons aged ≥12 years and authorized for use in children aged 6 months–11 years under Emergency Use Authorization (EUA) 1. Key points to consider include:

• The vaccines are designed to target more recent variants, including Omicron subvariants
• Eligible individuals should receive the most recent vaccine formulation available, regardless of previous vaccination history
• Most adults and children 6 months and older should get one updated dose, while those who are immunocompromised may need additional doses
• The vaccines provide strong protection against severe illness, hospitalization, and death, even as the virus evolves
• Breakthrough infections can still occur with newer variants, but vaccinated individuals typically experience milder symptoms and recover more quickly than unvaccinated people. The ACIP will continue to evaluate new evidence as it becomes available and will update recommendations as needed 1.

From the Research

Effectiveness of COVID-19 Vaccines Against Recent Strains

The effectiveness of COVID-19 vaccines against recent strains has been evaluated in several studies.

• A systematic review and meta-analysis published in 2025 found that COVID-19 vaccines had a high but heterogeneous level of protection against different viral variants, with nucleic acid vaccines showing the highest protection levels 2.
• Another study published in 2022 compared the characteristics, efficacy, and effectiveness of 19 COVID-19 vaccines against SARS-CoV-2 and variants of concern, and found that all vaccines had a high efficacy against the original strain and variants of concern, but with reduced effectiveness against the Delta strain 3.
• A systematic review published in 2021 found that full vaccination offered strong protection against the Alpha variant, but the results were not conclusive against the Beta and Gamma variants, and protection against the Delta variant was limited 4.

Vaccine Efficacy Against Specific Variants

The efficacy of COVID-19 vaccines against specific variants has been evaluated in several studies.

• A study published in 2021 found that the efficacy of COVID-19 vaccines against the Alpha variant was high, with 13 out of 15 studies reporting more than 84% efficacy 4.
• The same study found that the efficacy against the Beta variant was lower, with 4 out of 7 studies reporting efficacies between 22 and 60% 4.
• The efficacy against the Gamma and Delta variants was also lower, with limited data available 4.

Challenges in Assessing Vaccine Efficacy

Assessing the efficacy of COVID-19 vaccines is challenging due to several factors.

• A review published in 2021 discussed the challenges in assessing the efficacy of candidate SARS-CoV-2 vaccines, including the difficulty in assessing protection against severe disease and death 5.
• The review also highlighted the need to interpret reported efficacy endpoints with caution and to consider the caveats needed to answer the question of whether a COVID-19 vaccine works 5.

Public Health Impact of Bivalent Vaccines

The public health impact of bivalent vaccines has been evaluated in a modeling study published in 2023.

• The study found that increasing uptake of bivalent COVID-19 vaccines in key risk groups, such as older adults, could have a substantial public health impact in reducing the burden of severe COVID-19 6.
• The study predicted that perfect coverage of bivalent boosters in the 75+ years group could avert 3,920 hospitalizations and 1,074 deaths, with a number needed to treat (NNT) of 387 and 1,410, respectively 6.