(CNN) - A one-of-a-kind COVID-19 vaccine trial is taking place in the U.S., but researchers need volunteers.
Tuesday the National Institute of Allergy and Infectious Diseases announced it has started phase one of a trial testing whether it is safe to mix COVID-19 vaccines from different manufacturers.
Researchers are now looking for participants.
They say volunteers must be at least 18-years old and have already received the Pfizer, Moderna or Johnson & Johnson vaccine.
During the trial, they will receive doses from different vaccines to review the effects of mixing boosters.
The National Institute is hoping to gather 150 fully vaccinated volunteers in all.
They expect to receive the initial trial results in late summer.
You can volunteer at clinicaltrials.gov.