By Michael Erman

NEW YORK (Reuters) – Pfizer BioNTech SE and Inc (NYSE) announced Tuesday that they have begun a clinical study to evaluate a modified version of their vaccine, specifically targeted at the COVID-19 Omicron variant. This variant has been unable to receive some protection from the two-dose original vaccine.

Companies plan to evaluate the Omicron-based vaccine’s immune response in three shots for unvaccinated patients and booster shots for those who have already had two doses.

The current vaccine is also being tested for a fourth time against an Omicron vaccine. It will only be used in cases where the Omicron vaccine was administered to patients who had received their third dose from Pfizer/BioNTech three to six weeks earlier.

Companies plan to examine the safety and tolerance of shots among the 1,400 participants in the trial.

Kathrin Jansen from Pfizer, head of vaccine development and research, stated that current data and actual-world data shows boosters provide excellent protection against Omicron severe disease and hospitalization. However, she also said, “We recognize the need for being prepared in case this protection wanes over the time and to potentially address Omicron or new variants in future.”

Pfizer indicated that only two doses (of the original vaccine) may be enough to prevent infection by the Omicron-related variant. Protection against death and hospitalization may also be decreasing.

However, the U.S. Centers for Disease Control and Prevention states that a third dose mRNA vaccination like the Pfizer/BioNTech has given 90% protection against COVID-19-related hospitalizations.

Some countries have already started offering additional booster doses, but a recent study https://www.reuters.com/world/middle-east/israeli-study-shows-4th-shot-covid-19-vaccine-not-able-block-omicron-2022-01-17 from Israel showed that while a fourth dose of an mRNA vaccine boosted antibodies, the level was not high enough to prevent infection by the Omicron variant.