Fresh hope of a Covid-19 vaccine has emerged from a new trial showing an experimental Chinese jab is "safe and elicits an antibody response" to fight the virus.
The findings come from a small early-phase randomised clinical trial published in The Lancet Infectious Diseases journal.
A previous clinical trial reported similar results for a different vaccine that is also based on inactivated whole SARS-CoV-2 virus, but in that study the vaccine was only tested in people aged under 60 years.
The latest study included participants aged between 18 and 80 years, and found that antibody responses were induced in all recipients.
Participants aged 60 and over were slower to respond, taking 42 days before antibodies were detected in all recipients compared with 28 days for participants aged 18-59. Antibody levels were also lower in those aged 60-80 years compared with those aged 18-59.
The trial was not designed to assess efficacy of the vaccine, so it is not possible to say whether the antibody responses induced by the vaccine, called BBIBP-CorV, are sufficient to protect from SARS-CoV-2 infection.
Professor Xiaoming Yang, one of the authors of the study, from the Beijing Institute of Biological Products Company Limited, Beijing, China, said: "Protecting older people is a key aim of a successful Covid-19 vaccine as this age group is at greater risk of severe illness from the disease.
"However, vaccines are sometimes less effective in this group because the immune system weakens with age.
"It is therefore encouraging to see that BBIBP-CorV induces antibody responses in people aged 60 and older, and we believe this justifies further investigation."
There are currently 42 vaccines for Covid-19 in clinical trials. These vary in type and include DNA plasmid vaccines, inactivated virus vaccines, adenovirus-vectored vaccines, RNA vaccines, protein subunit vaccines and virus-like particle vaccines.
Some of these have already been shown to be safe and to elicit immune responses in early phase clinical trials. The BBIBP-CorV vaccine used in this study is based on a sample of the virus that was isolated from a patient in China.
The authors noted some limitations with the study, including the short duration of follow-up at just 42 days. They also highlighted that the study did not include children and adolescents aged under 18. Trials with these groups will be carried out when the full analysis of data from adult groups is completed, the researchers say. Experts stress more studies are needed.
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