The level of antibodies against coronavirus triggered by the Chinese vaccine CoronaVac by Sinovac Biotech declines in most people six months after the second dose, but the third one increases it dramatically.
This is stated in the results of a study of blood samples belonging to 150 healthy people aged 18 to 59, divided into groups. The study was conducted by the Chinese scientists, Reuters reports.
In particular, the level of antibodies tends to decline below the key threshold (geometric mean titer around 8.0). In addition, it turned out that the longer the interval between doses, the more stable the antibodies are. For instance, among participants who received two doses with a difference of two and four weeks, only 16.9 and 35.2%, respectively, still had antibody levels above the threshold after six months.
As for the third dose, after the participants in one group had been given the third dose (over 500 people) about six months after the second, it turned out that their antibody level after 28 days increased approximately 3-5 times—up to 140.
Context. Earlier we reported that the formulators of vaccines against coronavirus Johnson&Johnson, Moderna, AstraZeneca, and Pfizer-BioNTech had announced about the effectiveness of their drugs against the delta strain.