A third dose of the Pfizer-BioNTech COVID-19 vaccine provided four times the protection against infection as two doses in people ages 60 and older, according to a new study by the Israeli Health Ministry.

The researchers also found that the booster shots improved protection against serious illness and hospitalization by five to six times. 

The numbers were for those who had received their third shot at least 10 days before. The data were presented at a meeting of a ministry panel of vaccination experts last week and published on the health ministry’s website Sunday.

The findings essentially confirm a separate study released last week by Israel's Maccabi health care provider, which found that the vaccine was found to be 86% effective in preventing infection after three shots in people 60 and over. 

Israel’s early vaccination efforts were a worldwide success story, but the country has recently pointed to data showing waning vaccine protection amid another coronavirus surge. Israel’s seven-day average for new infections as of Sunday was around 7,300 — a seven-month high.

Pfizer, too, has said its vaccine’s efficacy drops over time. 

On July 30, Israel began offering booster shots to people 60 and older who were at least five months removed from their second doses. The country lowered the eligibility age to 40 on Thursday. Prime Minister Naftali Bennett, 49, received his third Pfizer shot Friday.

Earlier this month, the U.S. began administering third shots of the Pfizer and Moderna vaccines to immunocompromised people. And President Joe Biden last week announced plans to offer booster shots starting in September to Americans who have received their second shots at least eight months earlier, pending approval from the Food and Drug Administration and the Centers for Disease Control and Prevention.

CDC Director Dr. Rochelle Walensky said last week that the agency has been closely monitoring Israel because it faced a surge related to the delta variant and vaccinated most of its residents earlier than the U.S. had. Sixty-five percent of Israelis have been fully vaccinated. 

“We are concerned that the current strong protection against severe infection, hospitalization and death could decrease in the months ahead, especially among those who are at higher risk or who were vaccinated earlier during the phases of our vaccination rollout,” Walensky said.

Tedros Adhanom Ghebreyesus, director-general for the World Health Organization, called Monday for a two-month moratorium on administering booster shots, saying they would contribute to vaccine inequality among rich and poorer nations. The U.S. said it is committed to protecting its residents and also helping vaccination efforts in other countries.

On Monday, the FDA granted full approval to the Pfizer vaccine, but that does not apply to booster shots. The agency will decide that matter separately.