Pfizer says it is developing a Covid booster shot to combat the highly transmissible Delta variant

Pfizer and BioNTech announced Thursday that they are developing a Covid-19 booster vaccine that will target the Delta variant amid concerns about the highly communicable strain that is already the predominant form of the disease in the United States.

The companies said that while they believe a third shot of their current two-dose vaccine has the potential to maintain the “highest level of protection” against all currently known variants, including Delta, they are “vigilant” and are developing an updated version of the Vaccine.

“According to real data from the Israeli Ministry of Health, the vaccine’s effectiveness in preventing infections and symptomatic diseases has declined six months after vaccination, although its effectiveness in preventing serious diseases remains high,” a written statement said Companies.

“These results are consistent with an ongoing analysis of the companies’ Phase 3 study,” they said. “This is why we have said, and continue to believe, that, given the totality of the data we have, it is likely that a third dose may be required within 6 to 12 months of full vaccination.”

Clinical trials could begin as early as August, subject to regulatory approvals, the companies said.

The announcement comes on the same day the Olympic Games organizers said they would be banning all viewers from the Games this year after Japan declared a state of emergency designed to stem a wave of new Covid-19 infections that are partly due to the Delta variant is due.

Delta is estimated by the World Health Organization to be about 55% more transmissible than Alpha, the variant first found in the UK that once dominated the US, didn’t do as well at protecting against mild illnesses and the spread of the disease to others, scientists say.

On Monday, Israeli officials reported a decrease in the effectiveness of the Pfizer BioNTech vaccine in preventing infections and symptomatic diseases, but said it remained highly effective in preventing serious diseases.

In the US, health officials are urging all eligible Americans to get vaccinated as soon as possible, especially before the fall season when Delta is expected to lead to a further surge in new coronavirus cases, especially in places with the lowest vaccination rates.

There are about 1,000 counties in the U.S. with a Covid vaccination rate of less than 30%, most of which are located in the Southeast and Midwest, said CDC Director Dr. Rochelle Walensky recently. In these areas, the authority already sees increasing infection rates due to the further spread of the delta variant.

Pfizer and BioNtech executives have repeatedly said that people will likely need a booster vaccination or a third dose within 12 months of full vaccination, as they expect vaccine-induced immunity to wear off over time. They also said that people are likely to have to take extra shots every year.

Pfizer and BioNTech are developing booster vaccines and are expected to apply for US approval for a third dose of their vaccine shortly.

Editor’s Note: This story has been updated to reflect a later statement from Pfizer.