Pfizer vaccine makes 10 times more antibodies than Sinovac, Univ. of Hong Kong study shows
The Pfizer coronavirus vaccine could be almost 10 times more effective at combating COVID-19 infection compared to China’s Sinovac vaccine, according to a study published last week in the Lancet by researchers from the University of Hong Kong.
The scientists enrolled 1,442 vaccinated healthcare workers from various medical facilities across their country. The report details the results of 93 participants for whom the team now has complete data on antibody concentrations, before getting the jab and after the first and second doses.
Sixty-three participants received the Pfizer vaccine and the other 30 the Sinovac, the report said. Participants ranged in age from 26 to 65.
In healthcare workers who received the Pfizer vaccine, antibody concentrations “rose substantially after the first dose and then rose again after the second dose of vaccination,” the researchers wrote. In contrast, healthcare workers who were jabbed with Sinovac “had low concentrations… after the first dose, rising to moderate concentrations after the second dose.”
Israelis have been almost exclusively vaccinated with the Pfizer vaccine. So far, according to the most recent Health Ministry report, some 5.7 million Israelis have had at least one shot.
The Pfizer vaccine is a novel mRNA vaccine. The Sinovac shot is an inactivated virus vaccine.
The team used two tests to evaluate antibody levels. One is known as ELISA, which detects antibodies that bind to the receptor binding domain of the spike protein. The other is the sVNT test, which measures antibodies that neutralize viruses generated from vaccination.
Finally, the Hong Kong team examined a subset of 12 participants from each cohort , Pfizer and Sinovac, using a PRNT serological test that measures virus-specific neutralizing antibody titers.
Those who were administered the Pfizer vaccine had nearly 10 times the amount of antibodies (269) compared to those who received Sinovac (27), a difference that the report’s authors said, “could translate into substantial differences in vaccine effectiveness.”
The data is only preliminary, and the authors said it did not include information on other potential correlates of protection, such as T cells. In addition, it did not take variants into account.
One of the report’s authors, epidemiologist Prof. Ben Cowling, said that the study should not deter people from getting inoculated with Sinovac.
“Don’t let the perfect be the enemy of the good,” he said in an interview with AFP. “It is clearly better to go and get vaccinated with an inactivated vaccine than to wait and not get vaccinated. Many, many lives have been saved by the inactivated vaccine.”