The vaccine, after both doses are given, has been more than 90 percent effective at protecting against Covid-19 and 95 percent effective at protecting against severe disease, the company said in a statement. The results are based on more than 900 total cases of Covid-19, including 100 severe cases, that have been identified in participants of Moderna’s phase three vaccine trial as of April 9.
Pfizer recently announced that its vaccine was more than 90 percent effective against Covid-19 after six months and 95 to 100 percent effective against severe disease. Both companies are now testing their vaccines in children.
It is not yet clear whether the overall effectiveness of the vaccines will drop as dangerous new variants, some of which may evade vaccine-induced antibodies, spread more widely throughout the United States.
Moderna’s results, which “remain preliminary,” the company noted, have not yet been reported in a scientific journal. But they are consistent with results that were published in The New England Journal of Medicine last week. In that report, which is based on 33 adults who had received the Moderna vaccine, researchers found that study participants continued to have high levels of antibodies against the coronavirus six months after their second dose.
The company also announced preliminary results from tests of potential vaccine boosters in mice. One shot is designed to protect against B.1.351, the variant first identified in South Africa. The other combines that more targeted vaccine with the original formulation. Both boosters increased antibody levels in the mice, but the latter seemed to produce the strongest immune response in the mice, the company said, though it did not provide more detailed data.