According to new Israeli research, the fourth shot of the COVID-19 vaccine has turned out to be very powerful in minimizing the symptoms of the disease.
However, it fails at providing stronger protection when it comes to catching COVID after people have completed a course of three doses.
The research found that three months after receiving the fourth shot, the Pfizer shot had 71% and the Moderna shot had 89% effectiveness in preventing major symptomatic disease.
20% of the people who had received three shots of the Moderna vaccine had substantial symptoms, while only 3% of the patients with four shots did.
Substantial symptoms were defined by researchers as those that required people to spend two or more days in bed.
23% of the people who had gotten three shots of the Pfizer vaccine had substantial symptoms, but only 9% of the patients who had gotten four shots did the same.
The research was peer-reviewed recently and published in Nature Communications. It involved a total of 776 healthcare workers who had been monitored early this year at the Sheba Medical Center, when the Omicron wave had been at its peak in Israel.
It should be noted that the results of the study could be different if it is carried out today because new vaccines have become available since then in order to fight newer variants of COVID-19.
The study also discovered that the fourth Pfizer shot only gave 3% protection to people against infection, as opposed to someone who has received three doses.
As for the Moderna vaccine, the protection stood at 25%. It should be noted that Pfizer is the primary supplier of vaccines in Israel.
The effectiveness of the vaccines referred in this study does not consider the overall level of protection that people with four doses have.
Instead, it measures the additional protection delivered by the fourth shot, as compared to the first three.
The calculation of the rates was done by comparing the rates of disease and infection between recipients of the three and four shots.
Almost 40% to 50% of the people who participated in the study were infected and there was only a small difference, depending on whether they had gotten three or four doses.
Head of Sheba Medical Center’s infectious diseases department, Prof. Gili Regev-Yochay said that their study had not shown that the fourth dose of the vaccine could protect against infection.
She was the lead researcher and said that almost half of the population had gotten infected with COVID-19, even though most had received three or four vaccine doses.
But, she said that the vaccine had been effective against symptomatic disease. They said that their study went beyond any other research conducted previously that had focused on the effectiveness of the fourth shot in preventing the disease.
According to experts, people may have been excited about the vaccines for blocking infection almost entirely, but the goal had always been to minimize serious disease due to which the new research was helpful.