Pfizer (PFE  ) and BioNTech (BNTX  ) announced this week the two companies have begun a clinical trial to test a new version of their COVID-19 vaccine designed to specifically target the Omicron variant. The trial will evaluate the safety, tolerability and efficacy of the vaccine candidate in more than 1,400 healthy adults ages 18-55 years old.

The companies plan to test the virus-neutralizing antibody response generated by the new vaccine candidate both as a three-dose regimen in unvaccinated trial participants and as a booster shot for those who have already been inoculated with two dose of the pair's original COVID vaccine. Moreover, the companies are testing a fourth dose of the current vaccine against a fourth dose of the new Omicron-specific vaccine in participants who have already received a third booster shot of the original vaccine three to six months earlier.

"While current research and real-world date show that boosters continue to provide a high level of protection against severe disease and hospitalization with Omicron, we recognize the need to be prepared in the event this protection wanes over time and to potentially help address Omicron and new variants in the future," said Dr. Kathrin Jansen, head of vaccine research & development at Pfizer, said in a press statement.

"Staying vigilant against the virus requires us to identify new approaches for people to maintain a high level of protection, and we believe developing an investigating variant-based vaccines, like this one, are essential in our efforts towards this goal," Jansen added.

Pfizer has said that a two-dose regimen of the pair's original COVID vaccine now longer offers the same amount of protection against infection for new variants, including Omicron and Delta, and that protection against hospitalization and death may wane overtime.

The companies have previously announced that they expect to produce four billion doses of the original COVID vaccine this year, and that this capacity is not expected to change if an adapted vaccine is required.