PFIZER AND BIONTECH announced they would seek authorisation for a third dose of their Covid-19 vaccine to boost its efficacy as the Delta variant becomes more prevalent across the world.

With the pandemic once again regaining intensity, Japan banned fans from most Olympic events and placed Tokyo under a virus state of emergency throughout the Games.

The decision comes just two weeks before the opening ceremony.

Delta is the most infectious strain of the virus since the start of the global pandemic in early 2020.

Originally detected in India months ago, it has quickly spread and today is accelerating outbreaks even in countries with high vaccination rates.

This led the World Health Organisation to warn that the world was at a “perilous point” as the official global death toll passed four million.

Pfizer and BioNTech said they expect that a third dose will perform well against the Delta strain, and that they will be seeking authorisation in the United States, Europe and other regions in coming weeks.

Initial data from an ongoing trial showed a third shot pushed antibody levels five to 10 times higher against the original coronavirus strain and the Beta variant, first found in South Africa, compared to the first two doses alone, according to a statement.

The companies said they expected similar results for Delta but added they are also developing a Delta-specific vaccine against the strain.

US regulators said they were still studying the need for booster shots.

“Americans who have been fully vaccinated do not need a booster shot at this time,” the Food and Drug Administration and US Centers for Disease Control and Prevention said in a joint statement.

“We are prepared for booster doses if and when the science demonstrates that they are needed.”

The news came after Japan, where the strain currently accounts for around 30% of cases, banned spectators from Olympic venues in Tokyo, where most competitions will take place.

In Australia, the government said it would rush 300,000 vaccine doses to Sydney as the country’s largest city struggled to bring a Delta outbreak under control.

The WHO said more than four million people have died from Covid-19 but cautioned that the figure was likely an underestimate.

The UN body’s chief Tedros Adhanom Ghebreyesus warned rich countries against complacency and warned that the world was at a “perilous” point.