Dec. 8, 2021 -- A raft of new studies, released overnight that looked at the ability of Omicron to evade currently available vaccines, suggest a substantial loss of protection against the highly mutated variant.
The new studies, from teams of researchers in Germany, South Africa, Sweden, and the drug company Pfizer, showed 25- to 40-fold drops in the ability of antibodies created by two doses of the Pfizer-BioNTech vaccine to neutralize the virus. They also found that some monoclonal antibody therapies are ineffective against Omicron.
But there seemed to be a bright spot in the studies, too. The virus didn’t completely escape the immunity from the vaccines, and giving a third, booster dose appeared to restore antibodies to a level that’s been associated with protection against variants in the past.
“One of the silver linings of this pandemic so far is that mRNA vaccines manufactured based on the ancestral SARS-CoV-2 continue to work in the laboratory and, importantly, in real life against variant strains,” says Hana El Sahly, MD, a professor of molecular virology and microbiology at Baylor College of Medicine in Houston.
“The strains so far vary by their degree of being neutralized by the antibodies from these vaccines, but they are being neutralized nonetheless,” she says.
El Sahly points out that the Beta variant was associated with a 10-fold drop in antibodies, but two doses of the vaccines still protected against it.
President Joe Biden hailed the study results as good news.
“That Pfizer lab report came back saying that the expectation is that the existing vaccines protect against Omicron. But if you get the booster, you're really in good shape. And so that's very encouraging,” he said in an afternoon news briefing.
But other scientists stressed that these studies are from lab tests and don’t necessarily reflect what will happen with Omicron in the real world. They cautioned about a worldwide push for boosters with so many countries still struggling to give first doses of vaccines.
Soumya Swaminathan, MD, the chief scientist for the World Health Organization, stressed in a news briefing that the results from the four studies varied widely, showing dips in neutralizing activity with Omicron that ranged from 5-fold to 40-fold.
The types of lab tests that were run were different, too, and involved small numbers of blood samples from patients.
She stressed that immunity depends not just on neutralizing antibodies, which act as a first line of defense when a virus invades, but also on B cells and T cells, and so far, tests show that these crucial components, which are important for preventing severe disease and death, had been less impacted than antibodies.
“So, I think it's premature to conclude that this reduction in neutralizing activity would result in a significant reduction in vaccine effectiveness,” she said.
Whether or not these first-generation vaccines will be enough to stop Omicron, though, remains to be seen. In a study led by Sandra Ciesek, MD, who directs the Institute of Medical Virology at the University of Frankfurt in Germany, the booster didn’t appear to hold up well over time.
Ciesek and her team exposed Omicron viruses to the antibodies of volunteers who had been vaccinated and then boosted with the Pfizer vaccine 3 months prior. She also compared the results to what happened to those same 3-month antibody levels against Delta variant viruses. She found only a 25% neutralization of Omicron, compared to a 95% neutralization with Delta. That represented about a 37-fold reduction in the ability of the antibodies to neutralize Omicron vs. Delta.
“The data confirm that developing a vaccine adapted for Omicron makes sense,” she tweeted as part of a long thread she posted on her results.
Both Pfizer and Moderna are retooling their vaccines to better match them to the changes in the Omicron variant. In a news release, Pfizer said it could start deliveries of that updated vaccine by March of 2022, pending FDA authorization.
“What the booster really does in neutralizing Omicron right now, they don't know, they have no idea,” says Peter Palese, PhD, chair of the Department of Microbiology at the Icahn School of Medicine at Mount Sinai in New York City.
He says he’s definitely concerned about a possible Omicron wave.
“There are four major sites on the spike protein targeted by antibodies from the vaccines, and all four sites have mutations,” Palese says. “All these important antigenic sites are changed.”
“If Omicron becomes the new Delta, and the old vaccines really aren’t good enough, then we have to make new Omicron vaccines. Then we have to revaccinate everybody twice,” he says, noting that the the costs could be staggering. “I am worried.”
On Wednesday, Tedros Adhanom Ghebreyesus, PhD, director-general of the World Health Organization, urged countries to move quickly.
“Don’t wait. Act now,” he said, even before all the science is in hand. “All of us, every government, every individual should use all the tools we have right now” to drive down transmission, increase testing and surveillance, and share scientific findings.
“We can prevent Omicron becoming a global crisis right now,” he said.