“Until we know more, we will use available vaccine stocks for people who have had close contact with known cases, and people who are most at risk for exposure through their work, such as health professionals treating monkey pox patients,” he said.
The United States and several European countries have begun immunizing close contacts of infected patients, an approach called ring vaccination.
Many of the most vulnerable groups may already be protected. In one study, Dr. Slifka and his colleagues bled 306 vaccinated volunteers, some of whom had been immunized decades earlier, including one who had been immunized 75 years earlier. Most of them retained high levels of antibodies to smallpox.
In another study, Dr. Slifka and his colleagues suggest that antibodies produced by even a single dose of the smallpox vaccine decrease very slowly in the body, falling by half after about 92 years.
What you need to know about the Monkeypox virus?
What is monkey pox? Monkeypox is a virus endemic to parts of Central and West Africa. It is similar to smallpox, but less serious. It was discovered in 1958, after outbreaks occurred in monkeys kept for research, according to the Centers for Disease Control and Prevention.
dr. Ferrucci and his colleagues at the NIH, as well as other teams, have also found that antibody levels persist for decades after vaccination. Some studies have shown that other branches of the immune system also decline slowly, but antibodies produced by smallpox vaccination may be enough on their own to protect against monkeypox.
If smallpox started to spread, it would make sense to immunize anyone exposed because of the high death rate, regardless of prior vaccination, said Gigi Gronvall, a biosecurity expert at the Johns Hopkins Center for Health Security.
“We don’t want to risk anyone being left unprotected,” she said.
But that’s not necessary now, she added: “This is monkey pox.”