Adjusting COVID-19 vaccines will keep them effective against new variants

Since the early days of the COVID-19 pandemic, experts have warned that the first batch of vaccines created against the virus may not be the last. Like all viruses, it would mutate, and eventually these mutations could make the virus different enough that a different vaccine was needed to fight it. With only two months of vaccination campaign, the researchers are preparing for this inevitability.

There is early evidence from South Africa that the candidate vaccines Novavax and Johnson and Johnson are not as effective against a variant form of the virus first identified in the country, called B.1.351. The shots still offer some defense and still protect against hospitalization and death. Preliminary research indicates that the COVID-19 vaccines already authorized in the United States, made by Moderna and Pfizer / BioNTech, will also block this variant.

The first known cases of infection with this strain were reported in the United States this week. And even though her vaccine appears to be partially effective against the variant, the modern pharmaceutical company announced this week that it is starting to work on another version of its vaccine COVID-19. It will be more specifically addressed to B.1.351. It’s a good move based on what the researchers know so far, says Dylan Morris, who studies viral evolution at the University of California, Los Angeles. “I would say it is more prudent than an emergency,” he says.

Blood collected from people vaccinated with the Modern COVID-19 vaccine had antibodies that blocked the B.1.351 virus, new research showed. However, it took about six times more of them to block this strain than the predominant form of the virus against which the vaccine was designed. The COVID-19 vaccine from Pfizer and BioNTech also produces antibodies that block viruses with mutations found in B.1.351, although it carries a little more of them too, preliminary research has shown.

Both authorized vaccines produce very high levels of antibodies to start with, so there is room for a slight drop in potency. That high starting point means that there is more protection against changes in the virus, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, at a news conference last week.

One of the reasons Modern may still want to update its vaccine is to maintain these impressive levels of antibodies, says Stephen Goldstein, who studies evolutionary virology at the University of Utah. An additional shot designed to target the new variant could theoretically increase the body’s antibody response, even against a more formidable enemy. “We are in good shape at least in the coming months with these new variants, but perhaps we would like to return to the very, very high levels of neutralizing antibodies that are the hallmark of these vaccines,” he says.

Part of the uncertainty arises because scientists still don’t know what levels of antibodies someone needs to generate to protect themselves from COVID-19. “We can’t just do an experiment in a laboratory and say it’s time to update the vaccine,” says Goldstein. “There is a little bit of guesswork involved.”

There are a few different ways for researchers to take some of the guesswork out of the equation. The scientists were able to measure the antibody levels of people who were vaccinated, but they still got sick with COVID-19, and identified the cutoff point where the vaccine was not protective. They could also compare the effectiveness of a new vaccine that generates a high antibody response with an older version of that vaccine with less potency. Animal models can also work. In December, a team investigated the relationship between protection and the number of antibodies in monkeys, finding that relatively low levels blocked the virus.

Image: Jessica Christian / The San Francisco Chronicle via Getty Images

“People are working to measure this and try to get a better picture than things that are easy to measure – like antibodies – tell us what we are most interested in, which is how well you can be protected from disease,” he said. Morris.

Scientists already have this information about better known viruses, such as the flu. Researchers and regulators know what levels of antibodies the flu vaccine needs to generate to provide sufficient protection against the flu. They do not need to conduct a full clinical trial to test the effectiveness of a new flu vaccine – instead, the Food and Drug Administration will approve new flu vaccines based on the antibody response they generate in a small group trial. of people. Once a flu vaccine reaches this limit and is approved, the company can modify it for each new seasonal flu strain without having to collect new clinical data. Ideally, researchers will eventually be able to do something similar for the COVID-19 vaccines.

It could be some months before we have a good sense of the amount of immune response that corresponds to the protection of COVID-19. When they do, the FDA can approve updated or booster vaccines based on data showing that a new version can force the body to generate that level of immune response, rather than requiring companies to undergo clinical trials.

“The FDA has already considered developing a potential route, in case it is necessary to make changes to the authorized COVID-19 vaccines or other products based on information about emerging variants”, tweeted FDA acting commissioner Janet Woodcock.

The decision to apply any booster doses and adjusted vaccines should also take into account the amount of a new form of the virus that is circulating in a given area, says Goldstein. At the moment, there are only two confirmed cases of people in the United States infected with the B.1.351 virus strain, although there may be others that have not been identified. “It’s still very rare outside of South Africa, so we don’t want to vaccinate people in the United States against the strain that is not present in the United States,” says Goldstein.

Eventually, it may become more widespread and it may make sense to give people that extra protection. That’s why it’s encouraging that Moderna is preparing the boosters now. “We want to be prepared if the virus becomes more prevalent,” says Goldstein. Other strains of the coronavirus that are better able to escape existing vaccines may also emerge in the future. “I think it will be great to have the technological and regulatory side of things aligned in advance, for if and when we need to launch a vaccine update,” said Morris.