Pfizer and BioNTech has announced that they are developing a Covid-19 booster shot intended to target the highly transmissible delta variant. The majority of the Covid cases in the US are from this particular variant.

The companies believe that a third shot of their current two-dose vaccine has the potential to preserve the “highest levels” of protection against all currently known variants, including delta.

This comes after Israeli officials reported a decrease in effectiveness of the Pfizer-BioNTech vaccine in preventing infections and symptomatic illness, although it remained effective in preventing serious illness.

“As seen in real world data released from the Israel Ministry of Health, vaccine efficacy in preventing both infection and symptomatic disease has declined six months post-vaccination, although efficacy in preventing serious illnesses remains high,” the companies said in a written statement.

“These findings are consistent with an ongoing analysis from the Companies’ Phase 3 study,” they said. “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.”

Clinical studies would begin as early as August, although it is subjected to regulatory approvals.

The World Health Organization has estimated the delta variant to be about 55 per cent more transmissible than alpha, the variant first found in the United Kingdom. Scientists said that while evidence has shown that the vaccine is highly effective against delta in preventing severe disease and death, it does not do so well in preventing the spread of the disease.

Executives from Pfizer and BioNTech have continually stated that people will need a booster shot within 12 months of getting fully vaccinated as the vaccine-induced immunity are expected to wear off over time.