The Jerusalem Post

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.”

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