A fourth shot of the COVID-19 Sinopharm vaccine will not provide any additional protection against the disease, according to a study from the Sun Yat-sen University in Guangzhou.
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Sinopharm is one of the drugs most widely used in some South American countries. This research only corroborates what Argentine health authorities have been recognizing as a fact: booster doses of other brands of vaccine are given to those who took two shots of Sinopharm.
In addition to that, Sinopharm's protection wanes six months after three doses and a fourth will not provide any additional shield against the Omicron strain, according to the study.
The Chinese researchers suggested that the use of inactivated virus vaccines like Sinopharm's was “feasible but not ideal” and suggested recombinant spike protein or mRNA vaccines based on the variants of concern would be good alternatives for a booster.
The Chinese scientists concluded that antibodies triggered by a third dose of Sinopharm's Covid-19 shot dropped sharply after six months, and a fourth shot did not significantly boost them against Omicron.
The study, which is yet to be peer-reviewed and did not include readings among older people or minors, showed that neutralizing antibody level dropped by 53% against Omicron around 26 weeks after the third dose of Sinopharm's BBIBP-CorV, versus levels seen two weeks after the third dose, researchers said. The booster shot was given to 38 healthcare workers in China who had completed the two-dose regimen of the vaccine five months earlier.
The fourth dose, administered six months after the third, did not significantly lift the neutralizing antibody level against Omicron, although it still recalled the level to around the peak after a third dose, it was reported. ■
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