The antibodies produced by the booster were effective against the original form of the virus, as well as against the variants of concern first identified in South Africa and Brazil. A second booster specifically designed to counter B.1.351, the variant identified in South Africa, produced an even stronger immune response against that variant.
Moderna tested booster doses of either its current vaccine or a version designed specifically against B.1.351 in a Phase 2 trial of 40 people who had already been vaccinated six to eight months before. Blood tests showed half of these volunteers had a low antibody response against B.1.351 and the P.1 variant before they got the booster shot.
Two weeks after the booster, their antibody levels had grown against the so-called wild-type coronavirus — the variant most common around the world — as well as B.1.351 and P.1, Moderna said in the statement.
The results are from an early stage of Moderna’s trial of the boosters and have not yet been published or vetted by other scientists. Moderna plans to post the findings to the preprint server bioRxiv, the company said.
In a statement, Moderna’s Chief Executive Officer, Stéphane Bancel, said the results are encouraging and credited the vaccine’s mRNA technology with offering speed and precision in keeping up with changing viruses.
“Our mRNA platform allows for rapid design of vaccine candidates that incorporate key virus mutations, potentially allowing for faster development of future alternative variant-matched vaccines should they be needed,” Bancel said.
The company has submitted the data, collected as part of a Phase 2 trial, to a pre-print site and said it would submit for publication in a peer-reviewed journal when it gets more data from the trial.