A Covid-19 booster vaccination with Pfizer/BioNTech for people over 60 years old considerably increases the protective effect, according to a study.
There were more than 10 times as many proven infections and almost 20 times as many severe illnesses among people with two jabs than among people who had received a third shot in Israel, Israeli researchers wrote in the New England Journal of Medicine.
In Israel, all vaccinated people now have the option to receive a booster shot no earlier than five months after the second dose.
The country is currently fighting a third coronavirus wave despite very high vaccination rates.
The Israeli researchers assume that the more contagious Delta variant and declining protection six months after the second vaccine dose cause the protection rate against an infection to drop to 50 per cent.
Carsten Watzl, secretary general of the German Society for Immunology, said it was already known that antibody levels are about 10 times higher after a third dose than after just two.
But the study now shows that this "translates into a very, very decent protective effect."
Watzl pointed out, however, that the possibility of side effects was not considered in the study.
So far, there are no reports from Israel that the third jab leads to more noticeable side effects than the second one.
Watzl also does not recommend the booster for younger people, but for all people over 80 years old and for people over 60 with previous illnesses.
In Germany, people in need of nursing, over 80-year-olds and people with immunodeficiency are sometimes already offered a third vaccination.