China's Sinovac Covid-19 vaccine and the formula by AstraZeneca have both been found to boost antibody responses in almost all vaccine recipients.
This was the outcome of a study into a vaccination programme run by the Center of Excellence in Clinical Virology of the Faculty of Medicine at Chulalongkorn University.
Up to 97.26% of the people receiving the AstraZeneca vaccine were found to have developed immune responses in tests conducted four weeks after their first shot, said Prof Sirirerk Songwilai, permanent secretary of Higher Education Science Research and Innovation Ministry.
No test results after the second injection were included in the study as they had yet to be carried out at the time, he said.
As for the Sinovac vaccine's efficacy, he said, the study found 99.49% of the recipients had developed antibody responses four weeks after their second injection even though only 65.9% had developed immune responses three weeks after the first shot.
Antibodies against Sars‐CoV‐2, the new coronavirus that causes Covid-19, were measured using Roche Elecsys Electrochemiluminescence Immunoassay (ECLIA) -- a qualitative detection of total antibodies developed against Sars-CoV-2 in human plasma or serum specimens.
Blood samples were drawn from both the control and experiment groups for antibody response testing before the vaccine injection and again four weeks after the first shot injection in the case of the AstraZeneca vaccine, he said.
The same pre-vaccination antibody test applied to the Sinovac vaccination group, while more antibody tests would be carried out again three weeks after the first shot and once again four weeks after the second shot, he said.
Natural antibody responses to coronavirus were also examined in a group of 263 Covid-19 infected patients to compare with immune responses induced by the vaccinated groups, he said.
Of the 263 infected patients, only 243 (92.4%) developed antibodies against the coronavirus, according to Prof Sirirerk.
When analysed by gender, all 42 female recipients and 29 out of all 31 male vaccine recipients (93.5%) in the AstraZeneca group developed immune responses four weeks after the first shot.
However, when analysed by age, all 44 vaccine recipients aged between 18 and 59 years in the same AstraZeneca group developed antibody responses.
In the Sinovac vaccine group, 124 out of all 188 vaccine recipients (65.9%) developed antibody responses three weeks after the first shot.
The programme had concluded that both the AstraZeneca and Sinovac vaccines were highly effective in boosting immune responses against the new coronavirus, he said.
Prof Sirirerk stressed the high efficacy at boosting antibodies against Sars‐CoV‐2 of the Sinovac Covid-19 vaccine was only proved after both jabs had been administered to the test subject, despite its apparent low efficacy after the first round of injections.