Mpox Vaccination for Vulnerable Populations

CE / CME

Protection Beyond Outbreaks: Routine Mpox Vaccination for Vulnerable Populations

Nurses: 1.00 Nursing contact hour

Pharmacists: 1.00 contact hour (0.1 CEUs)

Physicians: maximum of 1.00 AMA PRA Category 1 Credit

Released: July 17, 2024

Expiration: July 16, 2025

Carlos del Rio
Carlos del Rio, MD
Aniruddha (Anu) Hazra
Aniruddha (Anu) Hazra, MD

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How Effective Is the Mpox Vaccine?

Aniruddha Hazra, MD:
Let’s review some of the data from several studies evaluating the effectiveness numbers for MVA-BN, including data specifically from the current outbreak.

Epic Cosmos: Mpox Vaccine Effectiveness

Carlos del Rio, MD, FIDSA:
The CDC published an MVA-BN effectiveness study, Epic Cosmos, in the New England Journal of Medicine, based on 2022 information from Cosmos, a nationwide Epic electronic health record database. This was a robust case-control study, and the results showed an effectiveness of 66% with both doses and 35.8% with 1 dose in an adjusted analysis.

Epic Cosmos: Effectiveness in Various Subpopulations

Carlos del Rio, MD, FIDSA:
The investigators also evaluated vaccine effectiveness in several subpopulations, including men, men aged 18 to 49 years who had not received smallpox vaccination, and individuals who were not immunocompromised. Not surprisingly, the vaccine effectiveness was slightly higher numerically in the group of individuals who were not immunocompromised.

New York 2022 Data: Mpox Vaccine Effectiveness

Carlos del Rio, MD, FIDSA:
The New York State Department of Health also performed a case-control study evaluating the effectiveness of MVA-BN based on systemic surveillance reporting data of male residents in New York, excluding New York City, from July through October 2022. The results showed a vaccine effectiveness of 88.5% for 2 doses and 68.1% for 1 dose.

Multijurisdictional Case-Control Study: Mpox Vaccine Effectiveness

Aniruddha Hazra, MD:
Another case-control study of MVA-BN effectiveness included men who have sex with men and transgender adults from 12 US jurisdictions from August 2022 through March 2023. In this study, the adjusted vaccine effectiveness was 85.9% for full vaccination with both doses and 75.2% for partial vaccination with only 1 dose. Vaccine effectiveness with both doses was 80% or greater regardless of administration type: subcutaneous, intradermal, or heterologous.

Multijurisdictional Case-Control Study: Mpox Vaccine Effectiveness in Immunocompromised Persons

Aniruddha Hazra, MD:
When the investigators assessed vaccine effectiveness according to immune competence, the adjusted vaccine effectiveness was 70.2% among immunocompromised individuals and 87.8% among immunocompetent individuals for the full, 2-dose vaccination.

Mpox Vaccine Effectiveness: Summary of Studies

Carlos del Rio, MD, FIDSA:
Those are important studies that I use when explaining to people that 2 doses of the mpox vaccine will provide 66% to 89% protection, although possibly lower for someone living with HIV who does not have full viral suppression.

That message helps emphasize the importance of establishing or strengthening HIV care for those without viral suppression and educates people that even in the best circumstances the efficacy of the mpox vaccine is not 100%. 

Aniruddha Hazra, MD:
An important caveat with the MVA-BN efficacy studies is that the observation periods for mpox incidence were not very long. As a result, we are still in a phase of collecting data and potentially refining what that final effectiveness number might end up being.

Nonetheless, the key message is that to obtain the most benefit from the MVA-BN vaccine, people need to receive both doses. For people living with HIV, particularly advanced HIV, although the vaccine effectiveness may not be as robust, it will still provide some protection against disease, morbidity, and certainly death.