Separate studies by two of Israel's largest health funds suggest that a fourth dose of the vaccine significantly reduces the risk of dying from the Covid-19 virus compared to the protection offered by three doses of immunization.
Israeli media report that these results are particularly relevant at a time when the omicron BA.2 substrain is causing an increase in the number of infected throughout Israel and in many other countries.
The Clalit fund study included 563.465 people aged 60 to 100 who received three doses of the vaccine.
They were divided into two groups, those who received the fourth dose, 58 percent of them, and those who did not.
The researchers compared the death rate in the two groups from January 10, the Sunday after the fourth dose was approved, and February 20.
The results showed that the fourth dose reduces the risk of dying from coronavirus among the elderly population by 78 percent.
The study, conducted in collaboration with Ben-Gurion University's Faculty of Health Sciences, has not yet been peer-reviewed and is currently being prepared for publication in a medical journal.
Doctor Doron Necer from Klalit explained the significance of the results due to the prevailing opinion that the omicron variant causes a mild disease, and that an additional vaccine is not needed.
"The results of the study show that the fourth dose is significantly associated with reduced mortality from the corona virus, including omicron," said Dr. Necer.
The Maccabi Foundation study examined the effectiveness of the vaccine for nine weeks from January to March among 100.000 members of the foundation aged 60 and older vaccinated with three doses.
A fourth dose was shown to be 73 percent more effective in preventing severe disease than three doses.
However, less than one percent of study participants who were vaccinated with at least three doses had serious symptoms of Covid-19.
The results also showed effectiveness against the coronavirus infection.
Three weeks after receiving the fourth dose, the risk of infection was reduced by 64 percent compared to those who received only three doses, but ten weeks after the vaccine the risk dropped to 29 percent, meaning that the additional protection wears off faster than after the third dose.
The researchers said new studies over a longer period are needed to determine the duration of protection offered by the fourth dose.
It was approved on January 2 for those over 60 and health workers at the beginning of the micron wave in Israel.
Nevertheless, despite the spread of the infection, 750.000 people agreed to the fourth dose, while 6,7 million of them received one dose, 6,1 million two and 4,4 million three doses out of a total of 9,4 million residents of Israel.
Israeli Prime Minister Naftali Bennett and Health Minister Nican Horowitz offered health facilities a bonus of $31 for each person over 60 who receives the fourth dose.
Bonus video:
