Turkey will start administering booster shots recommended for people vaccinated with two doses of Pfizer-BioNtech’s COVID-19 jab starting Thursday, Health Minister Fahrettin Koca announced Wednesday.

In the post shared on his official Twitter account, Koca said that certain risk groups would get “reminder shots” starting with people whose second dose of messenger RNA (mRNA) vaccines was administered six months ago. Priority will be given to citizens above the age of 60 and then to those with chronic diseases. Other high-risk groups will be given booster shots in the third stage.

Koca stressed that everyone above the age of 60 and pregnant should get fully vaccinated.

He also said that 67% of Turkish citizens have received one dose of the COVID-19 vaccine, with 57% having been fully vaccinated. “To achieve herd immunity this ratio needs to go over 70%,” Koca added.

Koca had previously announced that Turkey is considering administering the third shot and that 31 million vaccinated people were examined in a study that found three doses lowered the risk of infection compared to two doses and prevented hospitalizations and intensive care stays for the infected. The minister has also said that the preliminary results of the study showed that the efficacy of two doses of the Pfizer-BioNTech vaccine may decrease with time.