WASHINGTON — With the ongoing monkeypox outbreak, several viewers have reached out to ask: if they received the smallpox vaccine years ago, what’s the guidance for getting a monkeypox vaccine now? It’s a question we’ve received from many Verify viewers–and something researchers are still learning.
THE QUESTION
Are you protected against monkeypox if you had a smallpox vaccine years ago?
THE SOURCES
THE ANSWER
Doctors say it’s unclear the extent to which the smallpox/monkeypox vaccine works if it was initially administered a half century ago, which is why the CDC recommends another shot in most cases after exposure or to high-risk individuals.
WHAT WE FOUND
Once routine, most Americans no longer needed a smallpox vaccine after the disease was considered “eradicated” in the U.S., so the shots haven’t been widely administered since 1972.
Smallpox and monkeypox come from the same family of viruses, and the same vaccines are used to prevent both. But if you got a shot to prevent smallpox 50 years ago or more, we don’t yet know what kind of protection that still provides, and more data would be needed to make a conclusion.
“It's possible that they'll have some immunity to monkeypox now, maybe protect them a little bit,” said Dr. William Moss, Johns Hopkins infectious disease specialist, “but I would not rely on us smallpox vaccination 50 plus years ago to protect someone now against monkeypox
Dr. Mark Abel, infectious disease specialist with Northern Light Health, agrees: that initial protection has likely waned significantly.
“The challenge is we don't know how long the effectiveness of the vaccine lasts against monkeypox,” said Dr. Abel.
And Dr. Dan Baruch of the Harvard Center for Virology and Vaccine Research adds, it could be hard to quantify how much protection someone still has.
“I think that it's reasonable to assume that people who had the smallpox vaccine long ago, since they do have long term immunity against smallpox, they probably have some level of immunity against monkey pox, he said, “but it is certainly likely to be lower than if someone very recently received the smallpox vaccine.”
With the ongoing outbreak worsening, health officials are taking a cautious approach.
“If you got the smallpox vaccine several decades ago, its protection against infecti on with monkeypox has likely waned to some degree, you're likely protected against severe disease, but you should still get vaccinated against monkeypox if you fall into that high risk category,” said Dr. Amish Andalja with the Johns Hopkins Center for Health Security.
The CDC currently says anyone exposed to monkeypox who hasn’t received the smallpox vaccine within the last 3 years should consider getting vaccinated again. Additionally, the agency advices some people should especially consider a vaccine:
That includes people who have been exposed to monkeypox, certain lab and healthcare workers, and people who’ve had multiple sexual partners in the past two weeks in an area with known monkeypox.