Moderna’s vaccine is effective against new variants of the coronavirus that have emerged in the UK and South Africa, the company said on Monday. However, it appears to be less protective against the variant discovered in South Africa, so the company is developing a new form of the vaccine that could be used as a booster shot against this virus.

“We’re doing it today to be ahead of the curve if we have to,” said Dr. Tal Zaks, Moderna Chief Medical Officer, in an interview. “I consider it an insurance policy.”

He added, “I don’t know if we need it and I hope we don’t.”

Moderna reported results from a study using blood samples from eight people who had received two doses of the vaccine and two monkeys who had also been immunized.

The British variant did not affect the amount of neutralizing antibodies – the type that can deactivate the virus – produced after vaccination. But with the South African form there was a six-fold decrease in those levels.

Even so, the company said, these antibodies remain “above levels expected to be protective”.

Moderna collaborated on the study with the Vaccine Research Center of the National Institute for Allergies and Infectious Diseases, which is part of the National Institutes of Health.

The results have not yet been published or peer-reviewed but have been submitted to bioRxiv, which publishes preliminary studies online.

The company’s action is part of a race to fight a changing virus that has already wreaked havoc around the world and is now threatening to mutate in ways that make the fight even more difficult.

Several new variants of the virus have emerged, with mutations that are worrying scientists. A form first spotted in the UK is about twice as contagious as the virus identified in China a year ago, and researchers have begun to suspect that it could also be more deadly.

Other variants with different mutations have emerged in South Africa and Brazil, and preliminary studies in the laboratory suggested that these forms may have some resistance to the immunity that people develop after recovering from infection or using Moderna or Pfizer BioNTech vaccinated vaccinations.

The British variant has been found in at least 20 states, but the Brazilian and South African versions were not discovered in the United States.

Dr. Zaks said the new version of the Moderna vaccine, which targets the South African variant, could be used as a booster if needed a year after receiving the original vaccine.

The need for such a booster can be determined by doing blood tests to measure antibody levels or by observing the population of vaccinated people to see if they will develop the new variant.

“We don’t have any data on the Brazilian variant yet,” said Dr. Zaks. “We expect it to come close to the South African, if at all. This is the one with the greatest overlap. New tribes will continue to emerge and we will continue to evaluate them. “

Noting that it took Moderna 42 days to make the original vaccine, he said the company could make a new vaccine, “hopefully a little faster this time, but not by much”.

Talks with regulators about what would be required to make a new version of the vaccine available to the public were just beginning.

“It’s early,” said Dr. Zaks.

This evolving story will be updated.