Smallpox Vaccination Effective Against Mpox

Researchers from Karolinska Institutet recently reported vaccines used against smallpox given until the mid-1970s offer continuing cross-reactive immunity to mpox.

A study published in the scientific journal Cell Host & Microbe on April 25, 2023, reports robust effector memory MPXV-specific T cell responses in mild mpox and long-lived TCF-1+ VACV/MPXV-specific CD8+ T cells decades after smallpox vaccination.

“Our study shows that this is the case, which implies that the memory cells are very long-lived and that they can recognize closely related viruses such as the mpox virus and provide overlapping, or cross-reactive immunity,” says the study’s corresponding author Marcus Buggert, docent and researcher at the Center for Infectious Medicine, Karolinska Institutet, in a press release on May 23, 2023.

By analyzing the T-cell immune response in 105 healthy blood donors, the researchers showed that individuals born before 1976 had a significantly more robust immune response against both viral types.

The researchers also analyzed the immune response in 22 men with a recent mpox infection. They showed that they also exhibited a robust immune response to the virus, which may provide future immunity.

The current study was too small to judge how much protection previous smallpox vaccination provides. Still, Dr. Buggert refers to a recently published British observational study examining the effect of a smallpox vaccine given to risk-group males in 2022.

“This study shows that smallpox vaccine can provide about 80% protection against mpox,” he says.

The Swedish Research Council, the Knut and Alice Wallenberg Foundation, the ERC, Karolinska Institutet, the Swedish Society for Medical Research, the Swedish Cancer Society, the Åke Wiberg Foundation, the Magnus Bergvall Foundation, and the Jonas Söderquist Foundation financed the study.

In February 2023, the U.S. Centers for Disease Control and Prevention updated the National Mpox Vaccination Strategy, recommending people exposed to the mpox virus and those more likely to contract the sexually transmitted disease should be vaccinated. 

In the U.S., JYNNEOS® has been the preferred mpox vaccine since 2022, while the first generation ACAM2000® has been offered for military and civilian use for many years.

However, both vaccines have been identified in mpox breakthrough reinfections in Chicago during 2023.

Mpox vaccine news is posted by Precision Vaccination.