Based on evidence of increased risk of reinfection six months after inoculation and the emergence of the extremely contagious Delta variant, Pfizer Inc plans to petition US regulators to approve a booster dosage of its COVID-19 vaccine within the next month, the drugmaker’s chief scientist said on Thursday.
The company has received initial data from an early human study showing that a third dose of its existing coronavirus vaccine is safe and can raise neutralizing antibody levels by 5 to 10 fold compared with the original vaccine, Pfizer research head Mikael Dolsten said in an interview.
The US Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) emphasised, however, in a joint statement that Americans who have been completely vaccinated do not require a booster COVID-19 shot at this time.
Some scientists have also questioned the need for booster shots.
Mikael Dolsten, Pfizer’s chief scientific officer, said the vaccine’s recently reported drop in effectiveness in Israel was primarily attributable to infections in persons who were immunised in January or February.
In June, the country’s health ministry reported that vaccine effectiveness in preventing infection and symptomatic disease had dropped to 64%.
“The Pfizer vaccine is highly active against the Delta variant,” Dolsten said in an interview. But after six months, he said “there likely is the risk of reinfection as antibodies, as predicted, wane”.
