Pfizer and BioNTech are set to start clinical trials next month on a version of their Covid-19 vaccine targeting the Delta variant. They are currently in the process of producing material for a clinical trial, which they expect to begin in August, pending regulatory approvals.

Pfizer Inc is also planning to seek U.S. regulatory authorisation approval for a booster dose of its COVID-19 vaccine within the next month. The need for a booster dose is based on evidence of greater risk of reinfection six months after inoculation and the spread of the highly contagious Delta variant, the company said.

Pfizer's chief scientific officer, Mikael Dolsten, said the recently reported drop in efficacy rates of vaccines in Israel was mostly due to infections in people who had been vaccinated in January or February.

Efficacy of the BioNTech/Pfizer mRNA vaccine against Delta variant of coronavirus is lower than initially thought, a new study in Israel revealed

The study showed that between May 2 and June 5, the vaccine had a 94.3% efficacy rate. From June 6, five days after the government canceled coronavirus restrictions, until early July, the rate plunged to 64%. A similar decline was recorded in protection against coronavirus symptoms, the report added.

The study however established encouraging outcomes for those vaccinated as far as hospitalisation goes. From May 2 to June 5, the efficacy rate in preventing hospitalization was 98.2%, compared with 93% from June 6 to July 3. A similar decline in the rate was recorded for the vaccine’s efficiency in preventing serious illness among people vaccinated.

The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) said, however, in a joint statement that Americans who have been fully vaccinated do not need a booster COVID-19 shot at this time.