Bottle of booster vaccine against smallpox and monkeypox MPXV.
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The Centers for Disease Control and Prevention on Thursday urged gay men and others at high risk for Mpox to get fully vaccinated to prevent a summer resurgence of the virus.
The CDC’s call for at-risk individuals to keep up to date with their vaccinations comes after a cluster of at least 21 MPox cases was reported in the Chicago area this month.
Many of the people who contracted MPOX in the Chicago cluster were fully vaccinated against the virus, raising the question of whether immunity to the vaccinations might wane over time.
The patients in the Chicago cluster all have mild symptoms, according to Demetre Daskalakis, deputy chief of the White House MPOX task force.
Daskalakis said no vaccine is perfect, but people who received two doses were at a much lower risk of catching and spreading the disease.
Three new reports released Thursday by the CDC and the New England Journal of Medicine showed that two shots of the Jynneos vaccine offer more protection than a single dose.
The CDC estimated in a study that a single dose of the vaccine was 75% effective in preventing Mpoxen, while two doses were about 86% effective. The New York State Department of Health found similar results in a second study: one dose was 68% effective and two doses were about 88% effective.
However, the New England Journal of Medicine study found that one dose was only 36% effective in preventing Mpox, while two doses were 66% effective.
Though estimates of the effectiveness of the MPOX vaccine vary, Daskalakis said the message is clear: “One dose is good, two doses are better.”
“Now is the time to get vaccinated,” Daskalakis said in a phone call to reporters on Thursday. “If you haven’t gotten your first dose – go get it. If you haven’t gotten your second dose – get that one,” he said.
Less than a quarter of the 1.7 million people most at risk of Mpox – mostly gay, bisexual and other men who have sex with men – have received two doses of the vaccine.
Daskalakis said most new cases of Mpox continue to be reported in men who have sex with men.
dr Christopher Braden, the CDC’s MPOX incident manager, said health officials would conduct studies to determine whether post-vaccination immunity might decline over time.
Braden said falling immunity is just one possible explanation for why an unexpectedly large number of people in the Chicago cluster contracted MPOX despite being fully vaccinated against the virus.
He said the CDC is also investigating whether the virus evolved over time to overcome immunity. It’s also possible that the vaccine the patients in the Chicago cluster received was compromised in some way or wasn’t administered properly, he said.
This is an evolving story. Please check again for updates.