Concerned about new variants of the virus that causes COVID-19, the U.S. Food and Drug Administration announced late Thursday that it is developing guidance to help vaccine, drug and testing manufacturers adapt. Existing vaccines, treatments and tests still work well, emphasized the FDA’s acting commissioner Janet Woodcock. But now is the time to get ready for a future when they may not. “We must prepare for all eventualities,” she said in a call with reporters. Within the next few weeks, the FDA will provide draft guidance to manufacturers on how to adapt their products as needed, Woodcock said.
Feedback from companies and others will help refine that guidance. Concern has been growing in recent weeks over variants of the SARS-CoV-2 virus that causes COVID-19, some of which appear to be more infectious. At least one, first identified in South Africa, rendered vaccines from Novavax and AstraZeneca-Oxford vaccines less effective in that country, although they still prevented severe disease and death. Moderna and Pfizer-BioNTech’s vaccines also held up when tested in Petri dishes against a new variant first seen in the United Kingdom and now spreading quickly throughout the U.S. Moderna’s vaccine did not fare as well against the variant first seen in South Africa, though it likely still offered some protection.
PCR diagnostic tests, the gold standard for detecting infection with SARS-CoV-2, also seem to continue to work well, Woodcock said, although they are relatively easy to update if the viral mutations become more problematic. With treatments, the primary concern is for monoclonal antibodies, used to prevent disease from progressing in high-risk patients. These drugs are extremely tightly targeted, so if the area of the virus they target changes, they might become ineffective, Woodcock said. Companies that make monoclonals are already responding by developing combinations of the drugs that target multiple areas. Lilly, which makes one authorized monoclonal antibody, announced recently that it hoped to add a second to ensure that the treatment would continue to be effective, despite changes in the virus.
With a vaccine, preventing serious disease and death is the main goal and the current shots still protect against that, said Dr. Anthony Fauci, the country’s top infectious disease doctor. To prevent the evolution of even more dangerous variants, it’s crucial to wear a mask, avoid indoor crowds, wash hands frequently and get vaccinated when possible, Fauci said at a White House briefing earlier in the week. “Viruses cannot mutate if they don’t replicate,” he said. “And if you stop their replication by vaccinating widely and not giving the virus an open playing field to continue to respond to the pressures that you put on it, you will not get mutations.”
What a new vaccine might look like
Although current vaccines appear to have at least some effectiveness against the known variants, there’s no question that the time will come when a new or tweaked one will be needed. All viruses mutate. The virus that causes COVID-19 has mutated fairly slowly over the last year, evolving only a handful of major new variants – not yet different enough to be scientifically considered new strains.
The flu, by contrast, evolves so quickly that new vaccines are needed every year, each of which addresses three or four different strains. It’s too soon to know whether people will need a booster shot every year or two or five to prevent COVID-19 and how that vaccine might need to be adapted as the SARS-CoV-2 virus changes.
All five of the vaccines which the U.S. government has contracted to buy, target the “spike” protein on the surface of the SARS-CoV-2 virus. Mutations to that protein in the South African variant are believed to be behind the reduced vaccine effectiveness. “What this is telling us is we need to be prepared,” said Dr. Jesse Goodman, a senior scholar with the O’Neill Institute for National and Global Health Law at Georgetown and former FDA chief scientist. “Because that preparedness is going to take time, the time to start on that is now.”
Several open questions will make the process more challenging. First, unlike with a well known disease like the flu, it’s not clear with COVID-19 what levels of antibodies in the blood are enough to provide protection. That means it’s hard to know whether someone is adequately protected until they get sick or don’t. Researchers are currently looking for so-called immune correlates of protection that can be used to gauge the effectiveness of a vaccine.
And although the variants known today don’t pose enough of a threat to vaccines, treatments or diagnostics, it will be tricky to predict which variants pose the biggest threats, Woodcock said. Some might be able to evade vaccines, treatments and diagnostics, but won’t spread enough in the U.S. to pose a problem here. Others might spread widely, but not be as concerning.
What’s the timing?
It’s not exactly clear how long it would take to make a vaccine that addresses a new variant, or several, because it’s never been done before. All of the COVID-19 vaccines that are being used in people so far were developed in under a year. Designing a new version should take much less time, vaccine makers said.
The technology behind Pfizer-BioNTech and Moderna’s vaccines, in particular, allows for rapid changes, with just a tweak to the template used to make it, but companies and regulators still have to work out the process that would be followed to vary the vaccines. “We will need to generate data that gives confidence that any updated vaccine is safe and effective,” Bourla said in the statement.
There are several different ways companies could change their COVID-19 vaccines to address new variants. First, as Moderna’s CEO has mentioned, they could add a booster shot aimed specifically at a particular variant. That might require a low-dose third shot for people who had already received two shots of Moderna’s vaccine. People who haven’t yet been vaccinated could get a shot that addresses several variants at once, like the annual flu shot.
The best option, Fauci said in a talk last week to the New York Academy of Sciences, would be to develop a “universal vaccine against against SARS-CoV-2 to address the inevitable evolution of mutations,” he said, adding, “But in the long game, we also would like to develop a universal vaccine against all coronaviruses (the family to which SARS-CoV2 belongs) since we’ve already experienced three separate (coronavirus) pandemics, one of which we still are right in the middle of.”
—
Photo Credit: Orpheus FX / Shutterstock.com