C.D.C. Says Early Data Offers Positive Signs About Monkeypox Vaccine

Natalie Dean, a biostatistician at Emory University, said it was difficult for researchers to establish how exposed people were to monkeypox or its differences in behavior, particularly when it comes to sensitive information.

“If you can refine it to a population with a particular exposure, then it’s easier to compare a vaccinated group with a certain level of exposure and an unvaccinated group with the same level of exposure,” he said. He added that it might be difficult to interpret the results if the people who got the vaccine were also the ones who made the most substantial changes in their behavior.

The study examined the results of a single dose of the two-dose vaccine, which left federal scientists without a clear picture of the efficacy of a full series or its durability. Federal officials have said that more complete protection is obtained after receiving a second dose.

“We did see some response after the first one in the lab, but the really high responses that we want to get from that level 10 force field, as opposed to a level five force field, don’t happen until the second dose,” he said. Dr. Demetre Daskalakis, White House deputy monkeypox coordinator, at the briefing. He added: “This just tells us to keep moving forward, because we need that second dose in the arms.”

Dr. Walensky said her agency did not yet have data on the severity of monkeypox cases in vaccinated people or figures showing how many people who got a first dose came back for a second. Many of those at high risk have received only one dose, although more second doses than first doses have been given in recent weeks. according to CDC data.

The research published Wednesday also did not describe how the people in the study were vaccinated, critical information needed to examine the federal government’s recent switch to a new vaccination method. In August, the Food and Drug Administration (FDA) began allowing providers to deliver a lower dose of the injection into the skin layers, as opposed to the fat, expanding the supply of vaccines at a time when doses were more limited. Many Americans in recent weeks have received the vaccine that way.

Dr. Walensky told the briefing that “we’re going to need a little more time and a little more numbers” to determine the effect of fractional dosing. The National Institutes of Health recently began a trial to examine how well a full dose of the vaccine works compared to divided doses, an effort that will estimate antibody levels in trial participants who were vaccinated.