Preliminary Trial Data Shows Fourth mRNA Vaccine Dose Fails to Prevent Omicron Infections
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Sheba Medical Center
Sheba Medical Center is not only the leading medical center in the Middle East but has also been ranked among the “World’s Top 10 Best Hospitals” by Newsweek for three consecutive years.In terms of scale, Sheba is the largest and most comprehensive medical center in Israel and even the entire Middle East, with 150 departments and clinics covering nearly all medical specialties. Among these, obstetrics, gynecology, pediatrics, neonatology, and rehabilitation enjoy high international reputations.Sheba’s research capabilities are equally impressive. As one of Israel’s most important research centers, its scientific achievements include TIL immunotherapy for metastatic melanoma, the targeted drug Olaparib for pancreatic cancer treatment, the Phase III clinical trial of the world’s first “gene breakthrough therapy” for hemophilia, and telemedicine projects for coronavirus.
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Tech Daily Tel Aviv, January 18th, by reporter Dingkun Hu — On the evening of January 17th local time, multiple Israeli media outlets, including The Jerusalem Post, reported that preliminary results from the world’s first clinical trial of a fourth dose of the COVID-19 vaccine conducted at Sheba Medical Center showed that receiving a fourth dose of Pfizer's mRNA vaccine could not effectively prevent infection with the Omicron variant.
Chief clinical trial investigator Professor Gili Regev-Yochay said that existing vaccines are very effective against previous strains but less so against the Omicron variant. The fourth dose can increase antibodies, slightly more than the third dose, but many people were still infected with the Omicron variant after receiving the fourth dose. Compared with the control group, the number of infections was slightly lower but did not significantly decrease.
As for the specific number of infections, antibody levels after vaccination, and the preventive effect of the fourth vaccine dose on severe cases, Regev said that these are still under study and cannot be provided temporarily. What has been announced now are preliminary research results.
Despite the poor trial results, Regev still believes that providing a fourth vaccine dose for high-risk populations such as the elderly may still be the right choice. The fourth dose could offer some benefits, but these benefits are not sufficient to support a plan to offer it to everyone.
Sheba Medical Center launched the aforementioned trial on December 27th of last year, administering a fourth dose of the Pfizer vaccine to 150 medical staff who had received their third vaccine dose more than four months prior and whose serum antibody levels were below 700. Subsequently, the center conducted a similar trial, administering a fourth dose of the Moderna vaccine to another group of 150 medical workers. Reggev revealed that the antibody levels after receiving either of the two vaccines were similar.
In early January, Reghev said that one week after the fourth dose, antibody levels increased fivefold. The result was similar to that after the third dose and far below the expected level of the trial. A week later, she said again that although antibody levels had risen further, they did not seem sufficient to counteract the transmissibility of the Omicron variant.
Currently, Israel is offering the fourth dose of the COVID-19 vaccine to people over 60, those with weakened immune systems, and medical personnel, with nearly 540,000 people across the country having received it. However, Israel remains caught in a peak of infections brought on by Omicron, with an average of over 40,000 new confirmed cases per day reported last week.