Sinovac says its COVID-19 vaccine is more effective with longer dosing interval



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BEIJING (Reuters) – Chinese Sinovac Biotech said on Monday that a clinical trial in Brazil showed its COVID-19 vaccine to be nearly 20 percentage points more effective in a small subgroup of patients who received their two more doses spaced.

The protection rate for 1,394 participants who received doses of CoronaVac or placebo three weeks apart was almost 70%, a spokesperson for Sinovac said.

Brazilian researchers announced last week that the vaccine’s overall efficacy was 50.4% based on the results of more than 9,000 volunteers, most of whom received doses 14 days apart, as reported in the test protocol.

The spokesperson said that a small number of attendees received their second photo late for various reasons, without giving further details.

The dosing interval for COVID-19 vaccines has become a hot topic of debate among scientists, regulators and governments.

British regulators have said that a COVID-19 vaccine from AstraZeneca and the University of Oxford is more effective when there is a gap between doses longer than initially expected.

Britain has also moved to allow a longer gap between doses of a COVID-19 vaccine from Pfizer and BioNTech, even though the companies say they only have efficacy data for a shorter period between injections.

The Sinovac spokesperson warned that the robustness of the subgroup’s data was weaker than the 50% result, which is based on the combined data of those receiving doses two or three weeks apart.

While Sinovac researchers had said early-stage trials showed that a four-week interval induces a stronger antibody response than two weeks, this is the first time the company has published efficacy data of a Phase III trial with dosing regimens different from its testing protocol.

Sinovac has yet to release the global results of its phase III trials, but its COVID-19 vaccine has been approved for emergency use in several countries, including Brazil, Indonesia and Turkey.

(Reporting by Roxanne Liu and Ryan Woo. Editing by Mark Potter)

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