Doses of the COVID-19 vaccine at Walter Reed National Military Medical Center, Bethesda, Md. DoD photo by Lisa Ferdinando.

Israeli researchers report that an additional dose of Pfizer (NYSE:PFE) and BioNTech’s (NISDQ:BNTX) COVID-19 vaccine leads to notable improvements in immunity in people 60 and older.

The protection against infection increased fourfold 10 days after administration of the third dose, according to scientists at the Gertner Institute (Ramat Gan, Israel) and KI Institute (Kfar Malal, Israel). In addition, patients who received a third dose had four to six times greater protection against severe illness and hospitalization.

In people over 60, a third dose was 86% effective in protecting against infection.

The country began distributing booster doses for people over 60 on July 30. In addition, Israel has recently made booster doses available to people 30 and older who had received the third dose at least five months prior.

The 7-day average COVID-19 case count in Israel recently exceeded 8,700 daily infections, marking a new record for one of the most vaccinated countries in the world.

Researchers in Israel have previously concluded that vaccination tends to offer diminishing protection over time. In July, researchers concluded that the Pfizer-BioNTech vaccine provided 40.5% protection against symptomatic COVID-19 but 88% protection against hospitalization.

The spread of the Delta variant likely contributed to the attenuated protection.

Pfizer CEO Albert Bourla has consistently predicted that COVID-19 boosters would be required.