Moderna says vaccine effective on variants, but tests booster shot

Moderna said Monday that its COVID-19 vaccine remains protective against two key variants of the virus, though out of “an abundance of caution” it is studying a new version of the vaccine to use as a booster dose against one of the variants.

Two more contagious variants of the virus have caused particular concern, one first discovered in the United Kingdom and one in South Africa. 

Moderna said Monday that its studies showed “no significant impact” in the levels of neutralizing antibodies produced against the U.K. variant, a positive sign. 

But for the South African variant, the vaccine produced a “six-fold” decrease in neutralizing antibodies. Still, the level of antibodies produced remains “above levels that are expected to be protective,” the company said. 

Given this drop in antibody levels, the company said that to be on the safe side, it will begin studying a new version of its vaccine specifically designed to fight the South African variant, that can be given as a booster shot.

The company said it would begin Phase 1 trials to “evaluate the immunological benefit of boosting with strain-specific spike proteins.”

“We are encouraged by these new data, which reinforce our confidence that the Moderna COVID-19 Vaccine should be protective against these newly detected variants,” said Stéphane Bancel, Moderna’s CEO. “Out of an abundance of caution and leveraging the flexibility of our mRNA platform, we are advancing an emerging variant booster candidate against the variant first identified in the Republic of South Africa into the clinic to determine if it will be more effective to boost [antibody levels] against this and potentially future variants.” 

Separately, Anthony Fauci, the government’s top infectious diseases expert, said on NBC on Monday there is some concern about the South African variant because there is a “very slight, modest diminution” in the efficacy of the vaccine against it. 

“But there is enough cushion, with the vaccines that we have, that we still consider them to be effective against both the U.K. strain and the South African strain,” he added. 

The type of vaccines used by Moderna and Pfizer, mRNA vaccines, are relatively easy to update if necessary. 

“We really need to make sure that we begin, and we already have, to prepare, if it’s necessary, to upgrade the vaccines,” Fauci said. 

The Biden administration is also expected to restrict travel from South Africa in a move to fight the spread of the variant.