The company said in a news release it found no reduction in the antibody response against the variant found in Britain. Against the South African variant, it found a reduced response but still believed its two-dose regimen would provide protection.

Moderna shares closed 12.2% higher at $147.00 on Monday.

The emergence of new variants in Britain, South Africa and Brazil has created some concern that mutations in the virus may make vaccines less effective.

Moderna said it is looking at whether a booster shot – either of its existing vaccine or of a new shot designed to protect against the South African variant – could be made available in future if evidence were to emerge that protection declined.

“The virus isn’t going to stand still,” Moderna President Stephen Hoge said on a conference call.

“While the current strains appear to be well-protected by our COVID-19, it’s important that we remain vigilant and develop potential tools and countermeasures that would allow us to continue to beat back the pandemic.”

Moderna said it expects its current vaccine will remain protective for at least a year after completing the two-dose course. It does not expect to test a third dose until at least six months after that course is finished.

Jefferies analyst Michael Yee said in a research note it was encouraging that the antibody response of the Moderna vaccine to the South African variant was still above the levels that provide protection.

Yee also said the speed with which Moderna was able to design a new booster shot candidate was proof of the flexibility of the new mRNA technology upon which it is based.

Dr. Paul Offit, an infectious disease expert at the University of Pennsylvania and a member of the U.S. Food and Drug Administration’s vaccine advisory panel, said he was only mildly concerned the vaccine would not be protective against the variants.

“It is a little worrisome that you see a lesser neutralizing antibody response, but that doesn’t necessarily mean that you are unprotected,” he said, noting that even these lower levels may still be enough to protect against serious infections.

“The goal of this vaccine is to keep you out of the hospital and to keep you out of the morgue. If you get a symptomatic infection or mildly symptomatic infection that is not a burden to the healthcare system,” Offit said.

Pfizer Inc and BioNTech SE have also said tests showed their vaccine is effective against the variant found in Britain, but have not yet disclosed results against the South African variant.

That variant first found in Britain has caused a massive surge in cases there and has also been found in more than a dozen U.S. states. U.S. public health officials expect it to be the dominant variant in the United States within six weeks.

REUTERS