Washington, Mar 10 (IANS): US researchers are conducting a clinical trial designed to help understand rare but potentially serious systemic allergic reactions to Covid-19 mRNA vaccines, the National Institutes of Health (NIH) announced.

The single-site trial will enroll up to 100 people aged 16 to 69 years who had an allergic reaction to a first dose of Covid-19 mRNA vaccine, reports Xinhua news agency.

Study participants will receive a second dose of vaccine as inpatients under carefully controlled conditions at the NIH's Clinical Center in Bethesda, Maryland.

At admission and during the inpatient stay, participants will have breathing tests and frequent blood draws, which will be used by medical staff to discern details of any allergic or other responses to the vaccine.

The enrollees will also complete mental health questionnaires prior to, at the time of, and in the months following vaccination, according to the NIH.

"People who experienced an allergic reaction after receiving a COVID-19 mRNA vaccine may be hesitant to complete their vaccine regimen," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

"This study will help us determine if individuals who experienced moderate systemic allergic reactions can safely receive a second dose of a Covid-19 mRNA vaccine," he added.