A recently published study by the Karolinska Institute suggests that vaccines against smallpox given until the mid-1970s offer continuing cross-reactive immunity to mpox, previously known as monkeypox.
Recently, the World Health Organization (WHO) lifted the Public Health Emergency of International Concern (PHEIC) for mpox on May 11.
However, Korea has recently seen an uptick in mpox cases, keeping quarantine officials on alert.
According to the Korea Disease Control and Prevention Agency (KDCA), as of Tuesday, the total mpox caseload stood at 87, with 43 confirmed cases in May alone.
The study explained that the orthopoxvirus that causes mpox is very similar to the virus that caused smallpox until the mid-1970s when it was finally eradicated.
Accordingly, the research team led by Dr. Buggert of Karolinska Institute’s Center for Infectious Medicine investigated individuals who were vaccinated decades ago against smallpox to determine if it would offer protection against mpox due to a remaining memory response.
By analyzing the T-cell immune response in 105 healthy blood donors, the researchers found that individuals born before 1976 had a significantly stronger immune response against both viruses.
Additionally, they analyzed the immune response in 22 men with a recent mpox infection and showed that they also exhibited a strong immune response to the virus.
“Our study shows that 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,” said Dr. Buggert.
Buggert also explained that the current study was too small to judge how much protection previous smallpox vaccination provides, but referenced a recently published British study examining the effect of a smallpox vaccine given to risk-group males in 2022.
“The results of that study showed that the smallpox vaccine can provide about 80 percent protection against mpox,” he said.
The study was published in the scientific journal, Cell Host & Microbe.