China's Sinopharm COVID jab, which is approved in more than 50 countries, produces less protective antibodies against coronavirus in elderly people, a study revealed.

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The study, led by researchers from the Obuda University, and ELKH Research Centre for Natural Sciences, Budapest, Hungary, was posted pre-print on Medrxiv this week and is yet to be peer-reviewed. The team measured neutralising antibody titres after two doses of the Sinopharm COVID jab -- known as BBIBP-CorV -- in 450 people.

Gender and time since the second dose had little association with the antibody titres. The team detected antibody levels in about 90 per cent of individuals below the age of 50, but antibody production after BBIBP-CorV vaccination was strongly reduced with increasing age. "A large number of elderly subjects, reaching 25 per cent at 60 years, and up to 50 per cent at ages over 80, were found not to produce any protective antibody," said Tamas Ferenci from the Physiological Controls Research Centre at Obuda.

"The real-world effectiveness of the BBIBP-CorV vaccine should be carefully monitored. Elderly subjects are especially prone to produce no protective antibody after vaccination. This should be monitored, and proper measures should be undertaken to prevent a potential outbreak of COVID-19 in BBIBP-CorV vaccinated but eventually unprotected elderly individuals," added Balazs Sarkadi from the Institute of Enzymology at ELKH. While the BBIBP-CorV vaccine was found to be effective, the Phase-III trial included few women, almost no elderly persons and none with pre-existing medical conditions, the researchers said.

This is of crucial importance as the vaccine is approved in more than 50 countries, and hundreds of millions have already been vaccinated with many planned to be vaccinated in the near future with this vaccine, they noted. Meanwhile, the vaccine has been found highly efficient against the Delta variant which has become the dominant variant across the world, said researchers from Sri Jayewardenepura University in Sri Lanka. According to the study, 95 per cent of the individuals who received two doses of Sinopharm vaccine have developed antibodies similar to a naturally infected COVID-19 person, the Xinhua news agency reported.