Moderna Vaccine Is Highly Protective and Prevents Severe Covid, Data Show

Moderna produced more evidence that its vaccine can prevent severe disease. Of 30 volunteers who developed severe cases of Covid, all had received the placebo, not the vaccine.

Dr. Limaye called that a crucial finding.

“We’re worried about severe cases that lead to hospitalization, which leads to death,” she said. “The fact that they were able to prevent any cases of severity — I mean, that’s huge.”

On this front, the Pfizer-BioNTech findings were less compelling. Ten severe cases were reported in the placebo group and one in the vaccinated group. Those numbers are too small to gauge the vaccine’s ability to prevent serious illness.

“The available data for these outcomes did not allow for firm conclusions,” the F.D.A. said.

A second difference is that the Pfizer-BioNTech vaccine started to protect against the coronavirus within about 10 days of the first dose. Moderna’s vaccine, by contrast, did not reveal such a striking effect after the first dose.

But fewer cases of Covid occurred among participants in the early days of the Moderna trial, making it harder to measure differences between the vaccinated and the placebo groups. In any case, health officials have said that for both vaccines, two doses are essential for full protection.

How long that protection will last is still an open question. In a recent study, Moderna found that three months after the second dose, volunteers were still making high levels of antibodies. But researchers don’t yet know what levels are needed to maintain immunity. Time, and more research, will tell whether booster shots will be required.

Another puzzle is whether the vaccine can prevent people from spreading the disease, which would greatly help to stop the pandemic. Those who are infected but have no symptoms are thought to be a major source of transmission.

Article source: https://www.nytimes.com/2020/12/15/health/covid-moderna-vaccine.html