Sinopharm’s Covid-19 vaccine was less effective in offering protection against the disease among the elderly, according to the results of a Hungarian study.
The study of 450 participants who had received two doses of the vaccine showed measurable antibody levels were present in about 90% of people under the age of 50, but the protection reduced as age increased.
The estimated probability of no antibody response was about 25% in people aged 60 and about 50% at the age of 80 years, according to the study, which was published on medRxiv earlier this week and has not been peer-reviewed.
Several elderly subjects were unable to produce any protective antibodies, suggesting that measures should be put in place to prevent an outbreak of Covid-19 among them, the study’s authors said.
But the authors warned that the reliable estimation of a direct relationship between the risk of the Covid-19 disease, hospitalization, or death and the antibody levels after vaccination is extremely difficult.
Sinopharm, formally known as China National Pharmaceutical Group, was not immediately available for comment.
The two-dose vaccine is one of the most widely used Covid-19 shots in China, and Sinopharm has agreed to provide up to 170 million doses of the shot to the global vaccine sharing scheme Covax through to the middle of 2022.
A recent study showed the vaccine elicited weaker antibody responses against the Delta variant, which was first found in India and is now the dominant variant worldwide.