BEIJING (Reuters) – China’s Sinovac Biotech said on Monday that a clinical trial in Brazil showed that its COVID-19 vaccine was almost 20 percentage points more effective in a small subset of patients who received two more separate doses.
The protection rate for 1,394 participants who received doses of CoronaVac or placebo three weeks apart was almost 70%, said a Sinovac spokesman.
Brazilian researchers announced last week that the vaccine’s overall effectiveness was 50.4% based on the results of more than 9,000 volunteers, most of whom received doses 14 days apart, as described in the trial protocol.
The spokesman said that a small number of participants received their second chance late due to several reasons, without giving details.
The interval between doses of COVID-19 vaccines has become a topic of debate among scientists, regulators and governments.
UK regulators have said that a COVID-19 vaccine from AstraZeneca and the University of Oxford is more effective when there is a longer interval between doses than originally anticipated.
Britain also decided to allow a longer interval between doses of the COVID-19 vaccine by Pfizer and BioNTech, although companies say they only have efficacy data for a shorter period between vaccines.
The Sinovac spokesman warned that the robustness of the subgroup’s data was weaker than the 50% result, which is based on the combined data of those who received doses at two or three weeks intervals.
Although Sinovac researchers said that early-stage tests showed that a four-week interval induced a stronger antibody response than two weeks, this is the first time the company has released data on the effectiveness of a Phase III test. with dosage standards that differ from your test protocol.
Sinovac has not yet released global results from its Phase III tests, but its vaccine COVID-19 has been approved for emergency use in several countries, including Brazil, Indonesia and Turkey.
(Reporting by Roxanne Liu and Ryan Woo. Mark Potter edition)