Mpox vaccine immunity appears to wane within one year, researchers warn

Immunity from the mpox vaccine appears to drop off after a few months, according to a small new study.

Using samples from 45 people who were either vaccinated against or infected with mpox in 2022, researchers from Harvard Medical School found that mpox antibodies waned six to 12 months after immunisation.

Two doses – which health authorities recommend four weeks apart – were better than one in the initial months after vaccination.

But a year later, the immune response for people who had two shots was similar to the peak response for those who got just one dose, “which provided limited protection,” according to the study, published in the medical journal JAMA.

The findings indicate that people who were vaccinated during the global mpox outbreak in 2022 may need additional shots to keep up their immunity, according to health experts who were not involved with the study.

“This study suggests that boosters might be required to maintain vaccine effectiveness,” Jonas Albarnaz, a fellow researching virology and immunology at the United Kingdom-based Pirbright Institute, said in a statement.

France already recommends mpox booster shots for people at higher risk of infection, including gay and bisexual men, sex workers, transgender people with multiple sexual partners, and their close contacts.

The new study analysed antibody levels in the weeks and months after vaccination with the Modified Vaccinia Ankara-Bavarian Nordic (MVA-BN) shot, which is the only mpox vaccine approved in the European Union and the UK.

The findings have some caveats.

For example, a decline in antibodies doesn’t necessarily mean that people will be less protected against mpox in real life, according to Jake Dunning, a senior research fellow at the University of