FRANKFURT, Jan 28 (Reuters) - The head of Germany's vaccines regulator said he supported the decision by BioNTech Pfizer to conduct pivotal tests on their adapted vaccine to target the COVID-19 Omicron variant in the United States.

"The companies have to carry out the clinical trials in a relevant setting. This is where the United States are quite suitable," Klaus Cichutek, president of the Paul Ehrlich Institute, told Reuters TV.

Pfizer and Germany-based BioNTech said on Tuesday they started a clinical trial in the United States to test the new version of their vaccine as Omicron eludes some of the protection provided by the original two-dose vaccine regimen.

"Omicron is dominant also in the U.S. so that I'm sure the results will also be a very good basis for a possible approval in Europe," he added.

The Paul Ehrlich Institute is contributing to the regulatory review to be done by the EU's European Medicines Agency, or EMA, as part of the involvement of national bodies in EMA's work.

The established version of the vaccine, when given three times, has been shown to offer good protection against COVID-19, especially against severe forms, but the global surge in Omicron cases is also driven by breakthrough infections in the vaccinated. (Reporting by Ludwig Burger, Editing by Louise Heavens)