Fourth mRNA COVID-19 Not as Effective Against Omicron, says Study

A fourth dose of an mRNA seems not to be as effective against the Omicron variant of COVID-19 as it is against earlier variants, according to an Israeli study. The study was conducted by investigators with Sheba Medical Center in Israel. Gili Regev-Yochay, a lead researcher in the experiment, said that “we see an increase in antibodies, higher than after the third dose. However, 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,” according to the Times of Israel.1 Regev-Yochay added: “The bottom line is that the vaccine is excellent against the Alpha and Delta, for Omicron it’s not good enough.”

She also noted that the study found no significant difference in breakthrough infections between Pfizer/BioNTech and Moderna recipients.

Regev-Yochay said that the findings are preliminary and as of this writing, the study has not yet been released. The Times of Israel reported that “hours after releasing the results, Sheba published a statement calling for ‘continuing the vaccination drive for risk groups at this time, even though the vaccine doesn’t provide optimal protection against getting infected with the variant.’”

Over 500,000 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.

This article originally appeared in Contagion®.