Sinovac Biotech’s experimental Covid-19 vaccine CoronaVac triggered a quick immune response but the level of antibodies produced was lower than in people who had recovered from the disease, preliminary trial results showed on Wednesday.

While the early to mid-stage trials were not designed to assess the efficacy of CoronaVac, researchers said it could provide sufficient protection, based on their experience with other vaccines and data from preclinical studies with macaques.