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 on people aged under 60 years.
The latest study reported in The Lancet Infectious Diseases journal 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.
"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," said study author Xiaoming Yang from the Beijing Institute of Biological Products Company Limited in China.
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," Yang added.
The BBIBP-CorV vaccine used in the study reported here is based on a sample of the virus that was isolated from a patient in China. Stocks of the virus were grown in the lab using cell lines and then inactivated using a chemical called beta-proprionolactone. BBIBP-CorV includes the killed virus mixed with another component, aluminium hydroxide, which is called an adjuvant because it is known to boost immune responses. The first phase of the study was designed to find the optimal safe dose for BBIBP-CorV.
It involved 96 healthy volunteers aged between 18 and 59 years and a second group of 96 participants aged between 60 years and 80 years. Within each group, the vaccine was tested at three different dose levels, with two vaccinations administered on day zero and 28. A fourth group within each age group (24 participants in each age group) were given two doses of a placebo vaccine. In total, in phase 1 of the study, 144 participants received the vaccine and 48 received the placebo.
The second phase of the study was designed to identify the optimal timing schedule for vaccination. Participants were asked to report any adverse events for the first seven days after each vaccination and these were verified by the research team.
"No serious adverse events were reported within 28 days of the final vaccination. There were no instances of clinically significant changes in organ functions detected in laboratory tests in any of the groups," the authors wrote.
Source Ians