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, early 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.

The study follows encouraging announcements this month from US drugmakers Pfizer and Moderna, as well as Russia’s Sputnik V, that their experimental vaccines were more than 90 percent effective based on interim data from large, late-stage trials.

CoronaVac and four other experimental vaccines developed in China are currently undergoing late-stage trials to determine their effectiveness in preventing COVID-19.

The Sinovac findings, published in a peer-reviewed paper in the medical journal The Lancet Infectious Diseases, came from results in Phase I and Phase II clinical trials in China involving more than 700 participants.

“Our findings show that CoronaVac is capable of inducing a quick antibody response within four weeks of immunisation by giving two doses of the vaccine at a 14-day interval,” said Zhu Fengcai of the Jiangsu Provincial Center for Disease Control and Prevention in Nanjing and one of the authors of the paper.