This will test the safety, tolerability and efficacy of the vaccine candidate, the two companies announced on Tuesday. The trial will include up to 1,420 test subjects, who will be divided into three groups.

The first group comprises a good 600 participants who have already received two vaccine doses of the previous vaccine between 90 and 180 days before the start of the study and are now to receive one or two doses of the Omikron vaccine. The second, almost equally large group consists of boosted people who receive another dose of the conventional vaccine or one dose of the Omikron vaccine. The third group, with a good 200 volunteers, is made up of unvaccinated people who have not yet contracted Covid-19 and who will then receive three doses of the Omikron vaccine.

"The study is part of our scientific approach to develop a variant-based vaccine that provides protection from Omikron similar to what we have observed with previous variants, while lasting longer," explained BioNTech CEO Ugur Sahin. Vaccines still offer a high level of protection against severe courses of Omikron, he added.

The Mainz-based pharmaceutical company and its US partner had announced about a fortnight ago that they had already started production of a Corona vaccine adapted to the Omikron variant for later commercial use. BioNTech had said that the two companies would be "ready to supply the market by March, subject to regulatory approvals". Pfizer expressed the expectation of having pre-produced about 50 million to 100 million doses of the new vaccine by the end of March or early April.

The European Medicines Agency (EMA) has not yet stated whether it considers a vaccine adapted to Omikron with a different composition than the vaccine currently used to be necessary.

For the current year, BioNTech and Pfizer expect to produce up to four billion doses of vaccine worldwide. "The expected production volume will not change if the vaccine needs to be adjusted," the companies further stated on Tuesday.

The coronavirus vaccines currently in use from various manufacturers were originally developed against the so-called wild type of Sars-CoV-2, which was first discovered in China in late 2019. While the agents used since the turn of 2020/2021 also showed their effectiveness against circulating mutants such as alpha or delta, the situation is different with Omikron - especially when it comes to protection against infection.

The variant was reported from South Africa in November. According to the Robert Koch Institute (RKI), it has an unusually high number of mutations in the so-called spike protein, a building block of the virus. Some of the mutations are relevant, for example, with regard to transmissibility and the ability to circumvent an already existing protection through vaccination or surviving infection. At the same time, experts assume that the variant causes milder disease courses on average than the previously dominant variant delta.

The President of the German Medical Association, Klaus Reinhardt, recently explained that even a booster vaccination does not reliably protect against a Corona infection. "Very likely, however, one will be spared a severe course of disease with hospitalisation, or even intensive medical treatment," he said.

Original text: dpa. Translation: Mareike Graepel