Bhubaneswar, July 2 -- New Delhi: Volunteers have begun participating in Brazil's first clinical trial of Oxford COVID-19 vaccine. The ChAdOx1 vaccine technology is based on an adenovirus, and it is considered very safe, even in people with a weak immune system.

The vaccine being used in the Brazilian trial, on 5,000 volunteers, is similar to the one used in the UK and South Africa. The ChAdOx1 vaccine technology is based on an adenovirus, another virus, which causes mild upper respiratory tract infections.

"We have removed some of the adenovirus genes so that when we use it as a vaccine, the adenovirus can't spread through the body. That makes it very safe, even in people with a weak immune system. But because it is still a live virus,...