China’s CoronaVac gives 83.5% protection against Covid — Lancet study cites interim data

Further data is needed on the interim phase 3 trial of CoronaVac as analysis included a short follow-up period and involved a relatively young and low-risk population.

A man carrying a child, both wearing protective masks and raincoats, walk inside the Hankou railway station in Wuhan, China | Representational image | Bloomberg

New Delhi: CoronaVac, the Covid vaccine developed by the Chinese pharma company, Sinovac Biotech, has been found to offer 83.5 per cent protection against symptomatic Covid-19 infection and 100 per cent protection against hospitalisation, according to a study published in The Lancet journal.

The interim data from a phase 3 trial of CoronaVac indicates that the vaccine induces a robust antibody response.

During the trials that involved more than 10,000 participants in Turkey, no severe adverse events or deaths were reported. Most reactions were mild — such as fatigue and pain at the injection site — and they occurred within seven days of an injection.

CoronaVac has been approved for emergency use in 22 countries including Thailand, Brazil, Uruguay, Ukraine and Albania, and has been in phase 3 trials since mid-2020 in Brazil, Indonesia, Chile and Turkey. In this trial, participants were given two 3 mg doses of CoronaVac 14 days apart.

“One of the advantages of CoronaVac is that it does not need to be frozen, making it easier to transport and distribute. This could be particularly important for global distribution, as some countries may struggle to store large amounts of vaccine at very low temperatures,” states Professor Murat Akova, Hacettepe University Medical School, Turkey, the lead author of The Lancet study.

As many as 10,029 participants who either got the vaccine or a placebo between 14 September 2020 and 5 January 2021 were included for the efficacy analysis.

In total, 150 Covid-19 cases were confirmed by a PCR test after an average follow-up of 43 days. Fourteen days after the second dose, nine out of 6,559 subjects who got the vaccine were diagnosed with Covid-19. Among the 3,470 who received the placebo, 32 people got Covid.

90% who received vaccine developed antibodies

Analysis of immune responses induced by the vaccine involved a sample of 1,413 participants — 981 from the vaccine group and 432 from the placebo group.

CoronaVac induced an antibody response among 90 per cent of those who received the vaccine. The antibody response decreased with increasing age in men and women, the team said.

The team, however, acknowledged that the study had a number of limitations. The analysis included a short follow-up period and involved a relatively young and low-risk population.

The team said that further data is needed on the duration of protection, and safety and efficacy of the vaccine in elderly people, adolescents and young children, and those with chronic diseases.

The team has already reported CoronaVac as safe for use in healthy children and adolescents.

(Edited by Paramita Ghosh)