Chinese mRNA Covid-19 shot beat Sinovac as booster but caused more fevers

An employee at a Shenyang facility producing a Covid-19 vaccine currently undergoing clinical tests, on April 19, 2022. PHOTO: AFP

BEIJING (BLOOMBERG) - China's home grown mRNA vaccine stimulated the production of more protective antibodies than an inactivated shot when given as a booster, though it appeared to cause more side effects, according to study released Tuesday (May 31).

The mRNA vaccine, co-developed by Walvax Biotechnology Co, Suzhou Abogen Biosciences Co and the Chinese military, generated antibodies against the Delta variant at levels that were 6.5 times higher than those induced by the inactivated vaccine from Sinovac Biotech Ltd, research posted on the medRxiv website found.

The immunisations were given as a third shot to 300 previously vaccinated people in the trial, which has yet to be peer-reviewed.

People infected with Omicron generate significantly lower levels of antibodies in general because of a mutation that allows it to partially evade the protection offered by existing shots.

Still, in the study, antibody counts in people given the Chinese mRNA vaccine were 4.4 times higher than those seen with the Sinovac shot.

The development of a local vaccine using state-of-the-art mRNA technology is considered one of the elements China needs to exit its punishing Covid Zero strategy, marked by a zero-tolerance approach to the virus that has caused widespread social and economic stress.

While such shots from Pfizer Inc -BioNTech SE and Moderna Inc are widely available in most of the world, they haven't yet been cleared in China.

The mRNA vaccine, now called AWcorna, caused more side effects than the inactivated shot, with one-third of those getting it developing fever and one-fourth experiencing headaches.

Of those inoculated with the inactivated vaccine, only 4 per cent developed fever and 7 per cent reported headache.

Everyone in the study had been previously vaccinated with two doses of an inactivated vaccine from either Sinovac or state-owned Sinopharm.

The findings add to a growing body of evidence that using vaccines that work differently, rather than giving a third dose of the same inactivated vaccine, lead to superior protection against both the original Sars-CoV-2 strain and subsequent variants.

More than 90 per cent of China's 1.4 billion people have been fully vaccinated with inactivated shots either from Sinovac or Sinopharm. More than half have received boosters, though most used the same vaccine.

Only a fraction have been given shots using a different viral vector from CanSino Biologics Inc or a recombinant protein vaccine from Chongqing Zhifei Biological Products Co.

Both of those were found to stimulate a stronger immune response against Omicron when used as a booster in earlier studies, compared to those given a third dose of an inactivated vaccine.

AWcorna, previously known as ARCoV, is the most advanced mRNA vaccine candidate from China. Researchers still haven't reported the results of a key study that enrolled tens of thousands of people from numerous sites outside of the country.

An earlier phase I study found it led to more side effects such as fever than similar mRNA shots from western rivals.

Beijing hasn't approved BioNTech's shot, even though domestic drugmaker Shanghai Fosun Pharmaceutical Group Co secured the right to develop and market it in China early in the pandemic.

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