A German company working with US pharmaceutical giant Pfizer has begun human trials of a potential Covid-19 vaccine that could supply millions by the end of the year, according to the two firms.

Pfizer says it will begin testing the experimental vaccine in the United States as early as next week, and says a vaccine could be ready for emergency use in the fall, the Wall Street Journal reported on Tuesday.

Mainz-based BioNTech reported that the first cohort of participants had been given doses of the potential vaccine, BNT162, in a Phase 1/2 clinical study in Germany.

“Twelve study participants have been vaccinated with the vaccine candidate BNT162 in Germany since the start of the study on April 23, 2020,” the company said in a statement.

No information on the results is currently available. BioNTech said around 200 healthy volunteers aged 18 to 55 years old would be given doses ranging from 1µg (microgram) to 100µg to find the optimal dose for further studies.

“In addition, the safety and immunogenicity of the vaccine will be investigated,” added the biotech company.

Pfizer and BioNTech plan to initiate trials for BNT162 in the US on regulatory approval, expected shortly, the statement said.

The German Federal Institute for Vaccines and Biomedical Drugs approved the trial — the country’s first clinical trial for a vaccine against Covid 19 — on April 22.

“The two companies plan to jointly conduct clinical trials for the COVID-19 vaccine candidates initially in Europe and the U.S., across multiple research sites,” Pfizer announced in its first-quarter report, published online Tuesday.

“The companies estimate that there is potential to supply millions of vaccine doses by the end of 2020, subject to technical success of the development program and approval by regulatory authorities, and the potential to rapidly scale up the capacity to produce hundreds of millions of doses in 2021.”

Pfizer isn’t the only group with a potential Covid-19 vaccine in the works. Last week, scientists at Oxford University’s Jenner Institute in the United Kingdom began testing its vaccine on humans Thursday and, depending on the trial results, could be ready as early as September. Officials say that more than a half-dozen vaccine programs are in the clinical trial phase and more than 80 are in preliminary phases.