Two doses of Sinovac and a booster dose of Pfizer vaccines generate the highest level of immune response against the Delta and Omicron variants, measured at 1,143 Geometric Mean Titer (GMT) and 531 GMT respectively, according to initial findings from Siriraj Clinical Research Centre.
The centre conducted studies on the use of Pfizer, both full and half doses, and AstraZeneca as a booster jab for people already inoculated with two doses of Sinovac or AstraZeneca vaccines, assess the immune response to the Delta and Omicron variants.
The findings include:
- Two Sinovac doses and half a dose of Pfizer booster generate an immune response measured at 1,002 GMT against Delta and 507 GMT against the Omicron variant.
- Two Sinovac doses and one full dose of Pfizer booster generate an immune response measured at 1,143 GMT against Delta and 531 GMT against the Omicron variant.
- Two AstraZeneca doses and half a dose of Pfizer generate a 674 GMT immune response against Delta and a 232 GMT immune response against Omicron.
- Two AstraZeneca doses and one full dose of Pfizer vaccine produce a 917 GMT immune response against Delta and a 521 GMT immune response against Omicron.
- Three AstraZeneca vaccine doses generate a 121 GMT immune response against Delta and 22 GMT against Omicron.
The Siriraj Clinical Research Centre is recommending that people who were inoculated with two doses of the Sinovac vaccine receive a Pfizer booster dose, which will produce the highest level of immunity against the Delta and Omicron variants.
Likewise, those already inoculated with two AstraZeneca doses should receive Pfizer as a booster for a higher level of immunity, according to the centre.
