Israeli Study Finds Fourth COVID-19 Dose Insufficient Against Omicron

An Israeli study is the first to administer 4 COVID-19 shots, but the boosted antibodies may still not be enough to prevent Omicron breakthrough infections.

Sheba Medical Center in Israel recently launched the world’s first study of a fourth COVID-19 vaccine dose. Less than a month after the study launched, the investigators reported that the fourth booster offered insufficient protection against the Omicron variant.

Dr. Gili Regev-Yochay, director of the Infection Prevention and Control Unit at Sheba Medical Center and one of the study’s lead researchers, said, “The vaccine, which was very effective against the previous strains, is less effective against the Omicron strain… The bottom line is that the vaccine is excellent against the Alpha and Delta, for Omicron it’s not good enough.”

A fourth dose of the mRNA Pfizer-BioNTech or Moderna vaccines boosts antibody levels above the US-recommended third dose. However, the highly infectious Omicron strain may still be able to cause breakthrough infections in individuals who have received 4 vaccines.

“We see many infected with Omicron who received the fourth dose. Granted, a bit less than in the control group, but still a lot of infections,” Regev-Yochay said. She noted that the study found no significant difference in breakthrough infections between Pfizer-BioNTech and Moderna recipients.

Over 500000 Israelis have received 4 doses of mRNA COVID-19 vaccine. Currently, Israel’s Health Ministry has authorized a fourth shot to medical workers, the immunocompromised, and people 60 years and older. The Health Ministry estimates that over 6.3 million Israelis (2/3 of the population) have received at least 1 COVID-19 vaccine, and nearly 4.4 million have received 3 doses.

Israel’s cases remain high, which Prime Minister Naftali Bennett partially attributed to the country’s testing efforts; over 5% of the Israeli population is tested for COVID-19 each day.

Despite the preliminary evidence that a fourth dose will not offer sufficient protection against Omicron, Israel will continue to offer it to vulnerable populations, predicting that the variant’s contagions will wane in the coming weeks.

Additionally, “protection from serious morbidity, especially for the elderly population and at-risk population, is still afforded by this vaccine, and therefore I call on people to keep coming to get vaccinated,” Health Ministry director-general Nachman Ash said in a statement.