Pfizer-BioNTech reports that a third dose of its COVID-19 vaccine significantly enhances immune protection against SARS-CoV-2. The companies are seeking FDA authorization and have announced a new vaccine version tailored to the Delta variant.
Pfizer and BioNTech revealed Thursday they are developing a coronavirus vaccine specifically targeting the Delta variant, which now represents nearly 50% of infections in France. Unlike the current vaccine, which targets only part of the spike protein, this new version addresses the entire protein. Clinical trials are slated to begin in August.
The companies also shared promising, unpublished data showing that a booster dose given six months after the second injection increases antibody levels by five to ten times against all variants, including Delta.
These findings have not yet undergone peer review or publication in a scientific journal, but Pfizer and BioNTech plan to submit them to the FDA soon.
The U.S. Centers for Disease Control and Prevention (CDC) and FDA responded cautiously in a joint statement, noting that fully vaccinated Americans do not currently need boosters. "We are prepared to consider booster doses if and when science shows they are necessary," the agencies stated.
Citing Israeli data, Pfizer and BioNTech indicated that their vaccine's effectiveness in preventing infection and symptomatic disease declines after six months. Israeli officials estimated it offers 64% protection against Delta for fully vaccinated individuals.
However, other studies contradict this, affirming high effectiveness against infections from all variants. "Pfizer appears opportunistic, capitalizing on preliminary, unverified Israeli data," said John Moore, a virologist at Weill Cornell Medicine in New York.
Experts also raised concerns about prioritizing U.S. boosters while much of the world lacks access to initial doses. "We can't ignore the global context," noted Natalie Dean, biostatistician at Emory University in Atlanta. "It's difficult to justify third doses when frontline workers treating COVID patients remain unvaccinated."
