Senior citizens who received a second booster of the Pfizer–BioNTech COVID-19 vaccination had a 78 percent lower mortality rate from the disease than those who got one only, a study from Israel showed on Sunday.

The country's largest healthcare provider, Clalit Health Services, said the 40-day study included more than half a million people aged between 60 and 100.

Some 58 percent of participants had received a second booster – or two shots in addition to the basic two-shot regimen. The remainder had received only one booster. Researchers recorded 92 deaths among the first group and 232 deaths among the second, smaller group.

A paramedic is conducting a COVID-19 vaccine booster shot at a medical center in the Bedouin town of Rahat in southern Negev, Israel, August 16, 2021. (Photo: CFP)

"The main conclusion is that the second booster is lifesaving," said Health Outcomes Researcher Ronen Arbel at Clalit and Sapir College.

The report was issued as a preprint and has not been peer-reviewed. The research excluded people who received Moderna's vaccine and those who had taken oral anti-COVID therapy.

Israeli health officials have put out a number of studies on vaccine efficacy throughout the pandemic that have impacted policymaking in other countries.