BEIJING, Feb 6 ― China's Sinovac Biotech yesterday said late-stage trial data of its Covid-19 vaccine from Brazil and Turkey showed it prevented hospitalization and death in Covid-19 patients, but had a much lower efficacy rate in blocking infections.

The 12,396-person trial found the CoronaVac vaccine was 100 per cent effective in preventing Covid-19 sufferers from being hospitalised or dying and 83.7 per cent effective in avoiding cases that required any medical treatment, but only 50.65 per cent effective at keeping people from getting infected, according to a statement.

The trials evaluated the efficacy of the two-shot vaccine candidate 14 days after inoculation of participants, including healthcare workers who treat Covid-19 patients.

In Turkey, the vaccine was tested in two stages among health care workers and the general population, and found to have a 91.25 per cent efficacy rate in preventing Covid-19 based on an analysis of 29 cases, the company said.

In early January this year, Brazilian researchers reported interim results from the CoronaVac vaccine trial showing it was 50.4 per cent effective at preventing symptomatic infections.

Efficacy rates of other vaccines have varied widely by country, an emerging pattern reflecting the impact of new variants.

Among coronavirus variants currently most concerning for scientists and public health experts are British, South African and Brazilian ones, which appear to spread more swiftly than others.

In comparison, the two currently authorized Covid-19 vaccines from Pfizer Inc and partner BioNTech SE and Moderna Inc proved to be about 95 per cent effective in preventing illness in their pivotal late-state trials. Those studies were done in the United States before broad reports of variants.

Brazil's national immunisation programme currently relies on CoronaVac and the vaccine developed by Oxford University and AstraZeneca Plc. Both have been approved for emergency use. ― Reuters