Pfizer, BioNTech Announce Development of Vaccine Targeting COVID-19 Delta Variant


The companies say COVID-19 booster shots may be necessary, although the FDA and CDC have disagreed.

In an effort to combat the COVID-19 Delta variant, Pfizer and BioNtech have announced the development of a booster vaccine and expect to launch clinical trials in August, according to a press release.1

Despite encouraging findings about the efficacy of currently available vaccines,2 the companies are developing a booster shot specifically designed for the Delta variant, according to reporting by The New York Times. The Delta variant is believed to be approximately 60% more contagious than the UK variant, which emerged earlier in 2021. It could be twice as transmissible as the original COVID-19 virus.1

The Delta variant is also the dominant strain in the United States, according to recent estimates from the CDC. Although hospitalizations and deaths have declined over the past few months, new cases may be rising.3 Experts do not know, however, whether this increase is because of the variant, as it could also be attributable to slowing vaccination rates and increased reopenings.1

According to a recent update from the companies, clinical trials have found that immune sera taken shortly after the second dose of the currently available Pfizer/BioNTech vaccine have shown strong neutralization against the Delta variant, although they did not give specific results. The companies expect a third dose to boost these antibodies even higher and are conducting preclinical and clinical tests to confirm this hypothesis.2

“While Pfizer and BioNTech believe a third dose of BNT162b2 has the potential to preserve the highest levels of protective efficacy against all currently tested variants including Delta, the companies are remaining vigilant and are developing an updated version of the Pfizer-BioNTech COVID-19 vaccine that targets the full spike protein of the Delta variant,” the companies said in the press release.2

The press release added that vaccine efficacy in preventing both infection and symptomatic disease has declined after 6 months, based on real world data from Israel. Although the vaccine’s efficacy in preventing serious disease remains high, the investigators said the emergence of highly transmissible new variants may necessitate a third shot.2

“That is why we have said, and we continue to believe that it is likely, based on the totality of the data we have to date, that a third dose may be needed within 6 to 12 months after full vaccination,” the companies said in the press release.2

Some researchers still question the need for booster shots, however. Independent study findings have suggested that immunity could remain strong for years after vaccination with 2 shots, according to the New York Times,1 and federal health officials with the FDA and CDC have said boosters are unnecessary at this point, according to a joint statement from both agencies.4

“Americans who have been fully vaccinated do not need a booster shot at this time,” the agencies said in a press release.4

They added that health care professionals should continue to urge patients to get fully vaccinated. In order to be fully protected from severe disease and death, the agencies said patients must receive both doses of either the Moderna or Pfizer-BioNTech vaccine, or the single-dose vaccine from Johnson & Johnson.4

“Virtually all COVID-19 hospitalizations and deaths are among those who are unvaccinated,” the agencies said in the release. “We encourage Americans who have not yet been vaccinated to get vaccinated as soon as possible to protect themselves and their community.”4


1. Mandavilli A. Pfizer and BioNTech will test a vaccine against the Delta Variant. New York Times. July 9, 2021. Accessed July 9, 2021.

2. Pfizer and BioNTech Provide Update on Booster Program in Light of the Delta-Variant. News release. BioNTech. July 8, 2021. Accessed July 9, 2021.

3. CDC. COVID Data Tracker. Updated July 6, 2021. Accessed July 9, 2021.

4. Joint CDC and FDA Statement on Vaccine Boosters. News release. CDC. July 8, 2021. Accessed July 9, 2021.

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