The monkeypox virus vaccine is reportedly about 85% effective, there are reported cases of breakthrough monkeypox infection, according to Prevention reporting.

The World Health Organization (WHO) has revealed that “there have been a number of confirmed breakthrough cases of monkeypox—cases that occur despite vaccination”.

Rosamund Lewis, M.D., C.M., WHO’s technical lead for monkeypox, said in a press briefing “We have known from the beginning that this vaccine would not be a silver bullet, that it would not meet all the expectations that are being put on it and that we don’t have firm efficacy data or effectiveness data in this context. What we are beginning to see is that some cases are being reported, perhaps as breakthrough cases, either following post-exposure vaccination, which is meant to reduce disease severity or following preventive vaccination, which is meant to reduce infection.”

Dr. Lewis added during the briefing:

• “We don’t yet have any randomized control trials specifically on that but the fact that we’re beginning to see some breakthrough cases is also really important information because it tells us that the vaccine is not 100% effective in any given circumstance, whether preventive or post-exposure.
• “What we’re seeing are breakthrough cases and that every person who wishes to lower their own level of risk has many interventions at their disposal, which include vaccination where available, avoiding activities where they may be at risk, reducing their number of sexual partners, avoiding group sex or casual sex, and, specifically, when a vaccine is administered, waiting until that vaccine has the time to produce a maximum immune response.
• “In the case of [monkeypox] vaccine, this is two weeks after the second dose…People do need to wait until the vaccine can generate a maximum immune response but we don’t yet know what the effectiveness will be overall.

Quoting Amesh Adalja, M.D., senior scholar at Johns Hopkins Center for Health Security, Prevention writes “There needs to be rigorous analysis of data to make sure enough time has elapsed for the vaccine to be expected to be protective. Many of the breakthrough cases “might’ve occurred in individuals who only received a single dose of the vaccine, which is going to be less efficacious than that approved two-dose regimen.”

Prevention suggests “While we are starting to see some breakthrough cases of monkeypox, the vaccine is still highly effective at preventing severe disease and infection. If you belong to an at-risk group or you believe that you have been exposed to someone infected with monkeypox, consult your doctor right away to see if the vaccine is right for you.”