Citing Delta variant, Pfizer to continue booster shots and new vaccine

Pfizer and BioNTech announced Thursday that they are developing a version of the coronavirus vaccine that targets Delta, a highly contagious variant that has spread to nearly 100 countries. The companies plan to begin clinical trials of the vaccine in August.

Pfizer and BioNTech also reported promising results from studies in people who received a third dose of the original vaccine. A booster given six months after the second dose of the vaccine increases the potency of antibodies against the original virus and the beta variant by five to ten times, the companies said.

The vaccine’s effectiveness could decline six months after vaccination, the companies said in a press release, and booster doses may be needed to fend off variants of the virus.

The data has not been published or peer reviewed. Vaccine makers have said they plan to submit their findings to the Food and Drug Administration in the coming weeks, a step toward getting clearance for the booster injections.

But the companies’ claims contradict other research, and several experts have objected to the claim that boosters are needed.

“There is really no indication for a third booster or a third dose of an mRNA vaccine, given the variants we have in circulation right now,” said Dr. Céline Gounder, infectious disease specialist at Bellevue Hospital Center in New York. “In fact, a lot of us wonder if you’ll ever need boosters.”

Federal agencies also issued a questionable note Thursday night. Typically, Americans who have been fully immunized do not need a booster at this time, the FDA and the Centers for Disease Control and Prevention said in a joint statement.

“We are ready for booster doses if and when science shows they are needed,” the agencies said.

The Delta variant, first identified in India, is believed to be around 60% more contagious than Alpha, the version of the virus that ravaged Britain and much of Europe earlier this year, and possibly twice as contagious as the original coronavirus.

The Delta variant is now causing epidemics among unvaccinated populations in countries like 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 had peaked at their lowest levels since the start of the pandemic. Hospitalizations and deaths related to the virus continued to decline, but new infections could increase.

It is not yet clear to what extent the variant is responsible; a slowdown in the vaccination campaign and rapid reopening also play a role.

Citing data from Israel, Pfizer and BioNTech suggested that the effectiveness of their vaccine “in preventing both infections and symptomatic illnesses decreased six months after vaccination.” Noting the rise in power of Delta and other variants, the companies said “a third dose may be needed within 6 to 12 months of full vaccination.”

Health officials in Israel have estimated that full vaccination with Pfizer-BioNTech provides only 64% effectiveness against the Delta variant. (Efficacy against the original virus is greater than 90 percent.)

But Israel’s estimates have been contradicted by a number of other studies finding that the vaccine is very effective in preventing infection – against all variants. A recent study showed, for example, that mRNA vaccines like the one from Pfizer trigger a persistent immune response in the body that can protect against coronavirus for years.

“Pfizer seems opportunistic in hanging an ad on the back of very early, undigested data from Israel,” said John Moore, a virologist at Weill Cornell Medicine in New York. “When the time is right to use boosters here, the decision is not for them to make.”

The companies have described their plan to develop a new vaccine for Delta as a kind of back-up effort if the original vaccine boosters fail. The new vaccine will target all of the spike protein, as opposed to part, and the first batch has already been produced.

The Delta variant poses challenges to the immune system. In the journal Nature, French researchers on Thursday reported new evidence that the Delta variant may partially bypass the body’s immune response due to alterations in the spike protein on its surface which make it more difficult for antibodies to attack.

The team analyzed blood samples from 59 people after receiving the first and second doses of the vaccine. Blood samples from only 10% of people immunized with a dose of AstraZeneca or Pfizer-BioNTech vaccines were able to neutralize the Delta and Beta variants in laboratory experiments.

“A single dose of Pfizer or AstraZeneca was either little or not at all effective against the Beta and Delta variants,” the researchers concluded. Data from Israel and Britain largely support this conclusion, although these studies also suggested that one dose of the vaccine was still sufficient to prevent hospitalization or death from the virus.

But a second dose increased the effectiveness to 95 percent. There was no major difference in the antibody levels induced by the two vaccines.

“If you receive two doses of an mRNA vaccine, you are very well protected against serious illness, hospitalization and death compared to any of the variants,” said Dr Gounder.

The researchers also examined blood samples from 103 people infected with the coronavirus. Delta was much less sensitive than Alpha to samples from unvaccinated people in this group, according to the study.

One dose of vaccine significantly increased sensitivity, suggesting that people who have recovered from Covid-19 still need to be vaccinated to fend off certain variants.

Taken together, the results suggest that two doses of the vaccine are potently protective against all variants, as is one dose for people who have recovered from Covid-19 and have some natural immunity.

Some experts have also questioned discussions about recalls for Americans when much of the world has yet to receive 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 receiving a third dose when there are frontline workers treating Covid patients who still have not been vaccinated. “

Each unvaccinated person provides additional opportunities for the virus to mutate into dangerous variants, Dr. Gounder noted.

“If we are worried about the variants,” she said, “our best protection is to get the rest of the world vaccinated, not to rack up more doses to give third doses of mRNA vaccines to people here in the States. -United”