China’s CAS COVID-19 vaccine induces immune response in intermediate tests

BEIJING (Reuters) – A candidate vaccine against coronavirus developed by the Chinese Academy of Sciences (CAS) was found to be safe and triggered immune responses in initial and intermediate tests, the researchers said on Tuesday.

A final stage test of the ZF2001 vaccine, which CAS is developing with a Chongqing Zhifei Biological Products unit, began last month in China. It aims to recruit 29,000 people in China, Uzbekistan, Indonesia, Pakistan and Ecuador.

The candidate did not cause serious adverse events, with common mild side effects, including pain on injection, redness and swelling, researchers at the Chongqing Zhifei unit, CAS and other Chinese institutes said in an article published on Tuesday before the peer review.

The combined data from the Phase 1 and 2 trials involved 950 healthy Chinese participants aged 18-59. Low-dose and high-dose versions were tested, and the Phase 2 study also tested two doses versus three doses for the low and high dose versions.

The highest dose given through three injections at 30-day intervals did not induce an improved immune response compared to the lowest dose, the newspaper said. The Phase 3 trial will look at the lowest dose version given in three injections, he said.

Neutralizing antibodies against the virus were detected in at least 93% of participants who received three injections in different groups. The levels of antibodies triggered by the vaccine were higher than those seen in samples from patients recovered from the disease, the researchers said.

However, these antibody-based readings alone are not sufficient to predict how effective ZF2001 will be in protecting people from the virus, the researchers said, warning that it has not yet been possible to determine the duration of immune responses.

The vaccine also elicited moderate cell-based immune responses, a crucial part of the human immune system that functions differently from antibodies.

ZF2001 is a protein subunit vaccine, which uses a harmless part of the SARS-CoV-2 virus instead of the entire germ.

Four other Chinese vaccines from Sinopharm, Sinovac Biotech and CanSino Biologics have also entered Phase 3 clinical trials.

(Reporting by Roxanne Liu and Ryan Woo; Editing by Edwina Gibbs)