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Pfizer and BioNTech announced on Thursday that they are developing a version of a targeted coronavirus vaccine. Delta, a highly contagious variant that has spread to nearly 100 countries. The companies expect to begin clinical trials of the vaccine in August.
Pfizer and BioNTech also reported promising results from studies of people who received the treatment. third dose of original vaccine. A booster given six months after the second dose of vaccine increases the potency of antibodies against the original virus and the Beta variant five to ten times, the companies said.
The companies said in a news release that vaccine efficacy may decline six months after vaccination, and additional doses may be needed to fend off virus variants.
The data were not published and not reviewed by the referees. The vaccine manufacturers said they expect to submit their findings to the Food and Drug Administration in the coming weeks. booster shots.
But the companies’ claims contradict other research, and several experts have disputed the claim that boosters will be needed.
An infectious disease specialist at Bellevue Hospital Center in New York City, Dr. “Given the variants currently in circulation, there are really no indications for a third booster or a third dose of mRNA vaccine,” said Céline Gounder. “In fact, many of us question whether you would need boosters.”
Federal agencies also received a dubious note Thursday night. In general, fully vaccinated Americans do not need a booster shot at this time, the FDA and the Centers for Disease Control and Prevention said in a joint statement.
“We’re ready for booster doses if and when science shows it’s needed,” the agencies said.
The Delta variant, first identified in India, is believed to be around 60 percent more contagious than Alpha, the version of the virus that swept through the UK and much of Europe earlier this year, and perhaps twice as contagious as the original coronavirus.
The delta variant is currently causing outbreaks among unvaccinated populations in countries such as Malaysia, Portugal, Indonesia and Australia. Delta is also now the dominant variant in the United States, the CDC reported this week.
Until recently, infections in the United States were at their lowest levels since the start of the pandemic. Hospitalizations and deaths from the virus continued to decline, but new infections may be on the rise.
It is not yet clear to what extent the variant is responsible; A slowing vaccination movement and rapid reopenings also play a role.
Citing data from Israel, Pfizer and BioNTech suggested that “the effectiveness of their vaccine in preventing both infection and symptomatic disease declines six months after vaccination.” Noting the rise of Delta and other variants, the companies said that “a third dose may be needed within 6 to 12 months after full vaccination.”
Health authorities in Israel estimate that full vaccination with Pfizer-BioNTech provides only 64 percent efficacy against the Delta variant. (Efficacy against the original virus is more than 90 percent.)
But Israel’s predictions conflicted with a number of other studies finding that the vaccine is highly effective in preventing infection against all variants. A recent study showed, for example, that mRNA vaccines like Pfizer trigger a persistent immune reaction in the body. protect from corona virus for years.
“Pfizer seems opportunistic by hanging an announcement behind very early and undigested data from Israel,” said John Moore, a virologist at Weill Cornell Medicine in New York. “When it’s time to use boosters here, it’s not theirs to decide.”
The companies have described their plans to develop a new vaccine against Delta as a kind of backup effort should the boosters of the original vaccine fail. The new vaccine will target the entire spike protein instead of a portion, and the first batch has already been produced.
The delta variant poses challenges for the immune system. French researchers reported Thursday in the journal Nature that the Delta variant may partially inhibit the body’s immune response due to changes in the spike protein on its surface, making it harder for antibodies to attack.
The team analyzed blood samples from 59 people after they received the first and second doses of the vaccines. Blood samples from only 10 percent of people vaccinated with a dose of AstraZeneca or Pfizer-BioNTech vaccines were able to neutralize Delta and Beta variants in laboratory experiments.
“A single dose of Pfizer or AstraZeneca was either weak or not effective at all against the Beta and Delta variants,” the researchers said. Data from Israel and the UK broadly support this finding, but these studies also suggest that one dose of vaccine is still sufficient to prevent hospitalization or death from the virus.
But a second dose increased the effectiveness to 95 percent.. There was no significant difference in antibody levels elicited by the two vaccines.
Dr. “If you get two doses of mRNA vaccine, you’re very well protected against severe illness, hospitalization, and death with any variant,” said Gounder.
The researchers also looked at blood samples from 103 people infected with the coronavirus. Delta The study found that it was much less sensitive to samples from unvaccinated people in this group than Alpha.
One dose of the vaccine significantly increased sensitivity, suggesting that people recovering from Covid-19 still need to be vaccinated to fend off some variants.
Taken together, the results show that two doses of the vaccine are strongly protective against all variants, as is one dose for people who have recovered from Covid-19 and are naturally immune.
Some experts have also questioned the debate about boosters for Americans, when much of the world has yet to take even a single dose.
“It’s impossible to ignore the global situation,” said Natalie Dean, a biostatistician at Emory University in Atlanta. “It’s hard for me to imagine getting a third dose when there are still frontline workers treating unvaccinated COVID patients.”
Dr. Gounder noted that each unvaccinated person presents additional opportunities for the virus to evolve into dangerous variants.
“If we’re worried about variants,” he said, “our best protection is to get the rest of the world vaccinated, not hoarding more doses to give people here in the US a third dose of mRNA vaccine.”
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