BERLIN (AP) — Europe can achieve herd immunity against the coronavirus within the next four months, the head of German pharmaceutical company BioNTech, which developed the first widely approved COVID-19 vaccine with U.S. partner Pfizer, said Wednesday.

While the exact threshold required to reach that critical level of immunization remains a matter of debate, experts say a level above 70% would significantly disrupt transmission of the coronavirus within a population.

“Europe will reach herd immunity in July, latest by August,” Ugur Sahin, BioNTech's chief executive, told reporters.

His company's vaccine makes up a large share of the doses administered in Europe and North America, where it is more commonly known as the Pfizer shot.

Sahin said data from people who have received the vaccine show that the immune response gets weaker over time, and a third shot will likely be required.

Studies show the efficacy of the BioNTech/Pfizer vaccine declines from 95% declines to about 91% after six months, he said.

“Accordingly, we need a third shot to get the vaccine protection back up to almost 100% again” Sahin said. He suggested this should be administered 9-12 months after the first shot.

“And then I expect it will probably be necessary to get another booster every year or perhaps every 18 months again,” he said.