Singapore — In a Jul 27 Facebook post, Madam Ho Ching explained the effectiveness of the Pfizer Covid-19 vaccine in comparison to the vaccine manufactured by Sinovac, specifically in terms of antibodies both produce.
An antibody is a protective protein produced by one’s immune system in response to the presence of a foreign substance.
Using data from a recent study, she wrote, “This is why I suggested that 2 shots of Sinovac may be equivalent to 1 shot of Pfizer.”
The data was taken from a study of neutralising antibody tests on healthcare workers in Hong Kong entitled “Comparative immunogenicity of mRNA and inactivated vaccines against Covid-19,” which was published on Jul 15 in the British medical journal, The Lancet.
Mdm Ho, the chief executive officer of Temasek Holdings and wife of Prime Minister Lee Hsien Loong, listed the four tests in the study as the PRNT50 and PRNT90 tests, the RBD ELISA test and the sVNT, a neutralising test.
She wrote that after getting the first Pfizer jab, the results on those tested were “highly variable,” but the second Pfizer shot resulted in much higher antibodies across the board.
However, for doses of Sinovac, getting just one dose showed results that were “practically not effective,” she wrote, but after the second shot, antibody “levels also shot up, but with a wide range that goes from 30% to about 90%.
The average or median is clustered at the 60% mark.”
Mdm Ho added in this context, “This is why I suggested that 2 shots of Sinovac may be equivalent to 1 shot of Pfizer.”
She also wrote that the PRNT50 test has been used by health authorities such as the Food and Drug Administration in the United States to evaluate whether a person who recovered from Covid has enough antibodies to donate blood for the treatment of severe Covid patients.
“Typically, a titer of 160 or better is preferred, with a minimum of 80. This means most Sinovac 2 shot vaccinees do not have enough NAbs to treat a Covid patient,” she wrote, having explained earlier that the second Sinovac jab “yields titer levels between 10 to 40, with a geometric mean around 30.”
Mdm Ho then advised those in Singapore who choose to get Sinovac shots to make sure to get both tabs, and then to “try to do a neutralising antibody or NAb test to figure if you need a 3rd shot or even a 4th shot to give you better protection.”
/TISG
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