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| A study will examine whether people who received two doses of the Moderna coronavirus vaccine could get a booster shot made by a different company. (Mike Blake/Reuters) |
«As we know, covid is not going to go away anytime soon, and we know that the antibodies decrease over time, so that a boost will be needed at some juncture. I can’t predict when,» said John Beigel, associate director for clinical research in the Division of Microbiology and Infectious Diseases at the National Institute of Allergy and Infectious Diseases. Beigel is working on a U. trial, set to launch this week, that will provide one piece of the answer, testing whether people can mix and match shots when the need arises.
Progress is being made on all three fronts
«People just have to recognize the limitations of the data we have right now, and the critical need to generate the data to inform the decisions that matter,» said Beigel. «We assume that it would be okay to give a boost with any other vaccine, but we want to make sure». For people such as Martin Silberberg, 76, a semiretired biochemist and textbook author who lives in Pelham, Mass. Silberberg would be happy to get a booster or even an antibody test to check if he’s still protected but keeps finding himself at the frontier of the unknown.
The Food and Drug Administration has advised against antibody tests, in part because it isn’t clear how to interpret whether a particular test result indicates immunity. They will be closely monitoring what happens among vaccinated people in the trials and in the real world, in part because declining antibodies won’t necessarily mean that people get sick, because other parts of their immune response can step up. If scientists encounter unexpectedly high numbers of «breakthrough infections» that overcome immunity in vaccinated people, particularly infections that result in severe disease, it would be a warning sign that people need boosters. A recent study of the Moderna vaccine found that antibodies capable of neutralizing the variant B. 1.351 decayed in nearly half of people below a laboratory test’s level of detection over six months.
But such lab tests can’t predict what will happen if those vaccine recipients encounter that variant. One possibility is that those people would get sick, but another is that even if protection wanes, the immune system «is going to recognize the virus quickly upon infection and still protect,» said John R. Mascola, director of NIAID’s Vaccine Research Center. But Mascola cautioned «we don’t know that for sure». «And if you take a less-than-optimal scenario, someone who didn’t respond optimally to the vaccine for whatever reason, and we add on top of that they get exposed to a variant of concern,» Mascola said, it could prove problematic.
Companies have already been testing boosters, including an additional shot of their own vaccines and revamped boosters designed against the variant. A study of yet another booster option that would offer protection against the original strain and the variant-specific virus is ongoing. The trial is designed to yield results by midsummer, in hopes it could inform decisions as soon as this fall if necessary, Beigel said. The trial will take groups of 50 people who are fully vaccinated with an authorized vaccine and try one combination in each group.
Tracking antibody levels after vaccination will show whether the boosters have the intended effect of topping off immunity, and could reveal if certain combinations are better than others. In HIV vaccine research, many trials combine different technologies. Haynes is developing a next-generation coronavirus vaccine and testing it as a booster to a messenger RNA vaccine, the technology used in the Moderna and Pfizer-BioNTech shots. He said his experience with messenger RNA vaccines tested in monkeys against HIV and Zika found that while antibodies do drift downward, they then plateau and remain stable for nearly a year.
If that happens with the coronavirus, it might mean boosters aren’t needed as soon as some people think. Haynes said researchers will need to consider the level of antibodies required to thwart variants and the extent of protection people get from other parts of the immune response. In the United States, chief executives of companies that make vaccines have predicted booster shots will be needed before the end of the year. Pfizer chief executive Albert Bourla recently told Axios that boosters could be needed as soon as September or October.
John P. He cautioned that the notion of declining immunity may be less scary than it sounds. The shield of protection from vaccines won’t suddenly vanish, and while trials have shown vaccines are slightly less effective against infections caused by some variants, they still strongly protect against severe disease and death. Because shots have been rolled out over several months, there won’t be a day when the world is suddenly unprotected at once, even as immunity wanes. «Antibody don’t fall off a cliff,» Moore said.
Source: Carolyn Y. Johnson | The Washington Post
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