Is the best strategy against omicron to boost with the original vaccine?


Federal health officials are urging all vaccinated adults to get the Covid booster shot amid growing concern about the omicron variant, a strain of the highly mutated coronavirus that is already been detected in a handful of states across the United States But some vaccine experts fear that many booster doses of existing vaccines will make future vaccines, if necessary, less effective.

The variant mutations suggest that he may be able to evade some of the immunity provided by vaccination or natural infection. As federal health officials and drug makers wait for the highly anticipated lab results to see what threat does omicron pose to vaccines, for now, existing boosters are the best defense against the new strain and the highly transmissible delta variant, according to Dr.Anthony Fauci, White House chief medical adviser, epidemiologists and immunologists.

But what is the best strategy for boosters in the future? And if boosters are needed for years to come, as Albert Bourla, CEO of Pfizer suggested, will they need to be changed?

Studies show that an extra dose of current Covid vaccines “increases levels of neutralizing antibodies against all variants,” Fauci, director of the National Institute of Allergy and Infectious Diseases, said on Friday during the briefing of the White House Covid-19 response team. “There is every reason to believe that if you get the vaccine and boosted, you would at least have some degree of cross-protection, most likely against serious disease, even against the omicron variant.”

This week the Minister of Health of Israel, who started giving third doses of Pfizer boosters in summer, said a fourth booster dose may be needed if Covid cases in the country continue to rise.

Pfizer-BioNTech, Moderna and Johnson & Johnson working on vaccines specific to omicron for use against the new variant if lab tests show a significant drop in protection against serious disease, although it may take months before they are ready for distribution.

Still, some health experts are discussing the advisability of using existing vaccines as boosters against new emerging strains, as injections are still formulated to target the original form of the virus identified in late 2019.

“The question is, if you keep priming and boosting with a strain, which is basically producing an immune response against the ancestral strain, will that limit your ability to produce an immune response to a virus, which is very different from the ancestral one? ” said Dr. Paul Offit, vaccine expert at Children’s Hospital of Philadelphia.

Offit describes a phenomenon that immunologists call “original antigenic sin” in which the body’s immune system relies on the memory of its first encounter with a virus, sometimes leading to a weaker immune response when it later encounters a virus. other version of the virus.

Vaccines can also activate this phenomenon, said Offit, also a member of the Food and Drug Administration’s vaccine advisory committee. One example is with the human papillomavirus, or HPV, following the release of an updated vaccine that targeted nine strains of the virus instead of just four in the initial shot, he said.

“If you have HPV4 then HPV9, knowing that the four strains of [HPV]4 were also in [HPV]9, you had a very good immune response to all four strains, but you didn’t have as good an immune response as the other five strains, ”he said.

Theoretically, this could also apply to Covid, Offit said.

He said some experts have argued that it may be better for those who are not at high risk of serious illness to wait for a booster until a variant specific to the variant is available. .

He, along with Philip Krause and Marion Gruber, two former FDA officials, wrote an op-ed published Monday in the Washington Post who argued that booster shots should be reserved for people at high risk of serious illness, such as the elderly and those who live or work in high-risk environments, such as healthcare workers. They said the original two doses of the mRNA vaccines still work for most healthy adults.

Michael Osterholm, epidemiologist and former Covid adviser to President Joe Biden, countered that the third dose of mRNA or the second dose of J&J should be considered part of the primary series of the original vaccine and that people should receive a recall as soon as they are eligible. A booster dose “may actually compensate for the immune breakout we’ve seen with this particular variant,” Osterholm told MSNBC’s Hallie Jackson on Friday.

Ali Ellebedy, associate professor of pathology and immunology at the Washington University School of Medicine in St. Louis, pointed out that for influenza, too, having too many antibodies against previous strains can interfere with vaccinations against other variants. flu.

However, he said he rejects the idea that this could happen for Covid, at least at this time.

The world’s population has not accumulated enough basal antibodies against SARS-CoV-2 “to block any further boosts, which the flu does for some people,” he said. He also noted that influenza vaccines are “poorly immunogenic vaccines”, nothing to do with mRNA vaccines.

Ellen Foxman, an immunologist at Yale University, said that although the booster with the original vaccine made future vaccines less effective, it is not “wise” to wait for a variant-specific vaccine to get a hit. inch. The bottom line, she said, is that there is a potentially fatal virus still spreading across the country and current vaccines have been shown to protect against it.

Will the existing shot be as good as it was against the original virus? “Maybe or maybe not, but it will probably at least provide some protection against it,” she said.

“If we knew we needed an updated booster and knew it was coming out next week, maybe you should wait,” she said. “But the truth is, this coronavirus is circulating now and it’s mostly the delta variant.”

Dr Peter Hotez agreed, adding that the 30- to 40-fold increase in virus-bound antibodies generated by the booster shots might be enough against the new strain.

“Either way, you can’t wait for your recall as the delta is still the dominant variant and I think will be for the foreseeable future,” said Hotez, co-director of the Center for Vaccine Development at Texas Children’s Hospital. . and Dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston.

He added that a variant-specific vaccine may not be needed and that omicron-specific boosters developed by drug makers may not work.

“A slam dunk is not guaranteed,” Hotez said. “Waiting for a specific omicron recall is a very high risk strategy. “

John Moore, professor of microbiology and immunology at Weill Cornell Medical College, said there were still unknowns about the uses of vaccines, and therefore the “best strategy for stimulation” will emerge over time.

“Everyone wants instant answers, but getting the right answers is more important. It takes time,” he said.

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