U.S. begins clinical trial evaluating second COVID-19 booster shots in adults

A medical staff member prepares a dose of COVID-19 vaccine at a vaccine clinic in San Antonio, Texas, the United States, Jan. 9, 2022. (Photo by Nick Wagner/Xinhua)

"This trial will help us understand if we can use prototype and variant vaccines alone or together to shift immune responses to cover existing and emerging COVID-19 variants," said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases.

LOS ANGELES, March 31 (Xinhua) -- A Phase 2 clinical trial evaluating various additional COVID-19 booster shots has begun enrolling adult participants in the United States, the U.S. National Institutes of Health (NIH) announced on Thursday.

The trial, sponsored by the NIH, aims to understand if different vaccine regimens can broaden immune responses in adults who already have received a primary vaccination series and a first booster shot, according to the agency.

"We are looking beyond the Omicron variant to determine the best strategy to protect against future variants," said Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the NIH.

"This trial will help us understand if we can use prototype and variant vaccines alone or together to shift immune responses to cover existing and emerging COVID-19 variants," Fauci said.

Despite waning protection against infection and mild illness during the Omicron wave, COVID-19 vaccines available in the United States so far have maintained durable protection against severe COVID-19, said the NIH.

However, the NIAID is preparing for the possibility of future variants evading protection against currently available COVID-19 vaccines.