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, this one would mutate, and ultimately these mutations could make the virus different enough that a different vaccine would be needed to fight it. Only two months after the start of the vaccination campaign, researchers are preparing for this inevitability.

There is preliminary evidence from South Africa that the vaccine candidates 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. Shots still offer some defense and still protect against hospitalization and death. Preliminary research indicates that COVID-19 vaccines already authorized in the United States, manufactured by Moderna and Pfizer / BioNTech, will also continue to block this variant.

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

Blood drawn from people vaccinated with the Moderna COVID-19 vaccine contained antibodies that blocked the B.1.351 virus, new research has shown. However, it took about six times more to block this strain than the predominant form of the virus the vaccine was designed against. Pfizer and BioNTech’s COVID-19 vaccine also produces antibodies that block viruses with mutations found in B.1.351, although it also takes a little more, according to preliminary research.

Both licensed vaccines produce extremely high levels of antibodies to begin with, so there is room for a slight dip in potency. This high starting point means there is more cushion against the changes in the virus, Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said at a press briefing last week.

One of the reasons Moderna might still want to update its vaccine is to maintain those 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 boost the body’s antibody response, even against a more formidable foe. “We’re in good shape for at least like the next few months with these new variants, but we might like to get back to those really, really high levels of neutralizing antibodies which are the most outstanding feature of these vaccines,” he said. said.

Part of the uncertainty comes from the fact that scientists still do not know what levels of antibodies a person must generate to be protected from COVID-19. “We can’t just do an experiment in a lab and say it’s time to update the vaccine,” Goldstein says. “There is a bit of guesswork involved.”

There are several ways that researchers can take some of the guesswork out of the equation. Scientists were able to measure the antibody levels of people vaccinated but still fell ill with COVID-19 and identify the threshold 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 a lower potency. Animal models can also work. In December, a team investigated the relationship between protection and antibody counts in monkeys, finding that relatively low levels blocked the virus.

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“People are trying to measure that and trying to get a better idea of ​​what is easy for us to measure – like antibodies – tells us about what interests us most, which is how well you can be. protected. against disease, ”Morris says.

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

It might be some months before having a good understanding of the amount of immune response that corresponds to protection against COVID-19. When they do, the FDA can approve updated or booster vaccines based on data showing that a new version can cause the body to generate that level of immune response, rather than asking companies to pass trials. clinics.

“The FDA has already considered developing a potential pathway, whether changes need to be made to licensed COVID-19 vaccines or other products based on information on emerging variants.” tweeted Acting FDA Commissioner Janet Woodcock.

The decision to push for booster shots and adjusted vaccines should also take into account how much of a new form of virus is circulating in a given area, Goldstein says. At present, 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 pretty 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,” Goldstein says.

Eventually, it might become more prevalent and it might make sense to give people this extra protection. That’s why it’s encouraging that Moderna is making the boosters now. “We want to be ready in case the virus becomes more widespread,” Goldstein says. Other strains of the coronavirus that are more likely to escape existing vaccines may also emerge in the future. “I think it will be really good to put the technological and regulatory aspects of things in place in advance, because if and when we need to roll out a vaccine update,” Morris says.