Antibody levels, generated by two jabs of Sinovac vaccine and a booster shot of AstraZeneca, is relatively lower than two Sinovac jabs and a booster of Pfizer vaccine, but the immunity generated after the Sinovac-Pfizer regimen drops faster, according to research jointly conducted by Thailand’s National Centre for Genetic Engineering and Biotechnology (Biotec) and Thammasat University.

Dr. Anan Jongkaewwattana, virologist and head of the Animal Health Innovation Research Division of Biotec, said on his Facebook page on Sunday that researchers conducted research on two groups of frontline medical personnel. One group received two Sinovac jabs and a third AstraZeneca jab and the other received third Pfizer jab, to assess the immune response after inoculation.

He disclosed that the results show that those inoculated with the third Pfizer jab have developed an antibody level of 3,500, compared to 1,500 in the other group.

He said, however, that 45 days after the vaccinations, the antibody levels of those receiving the AstraZeneca jab remain at 1,500 while, for the other group, the level of antibodies dropped from 3,500 to 2,800 one month after receiving the third jab.

Dr. Anan maintained that the 1,500 level of antibodies generated by the AstraZeneca booster jab is enough to cope with the Delta variant of COVID-19, particularly when compared to the baseline level before administration of the third dose.

While admitting that Pfizer generates a higher level of immune response, the antibody level drops faster, adding that further research is needed to determine how long it will take for the immunity to drop below the level generated by the AstraZeneca vaccine.