 Antibody
triggered by Sinopharm COVID booster wanes after six months - study
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[February 22, 2022]
BEIJING (Reuters) - Antibodies triggered by
a third dose of Sinopharm's COVID-19 shot given to those who completed
its primary two-dose regimen dropped sharply after six months, and a
fourth shot did not significantly boost them against Omicron, a Chinese
study showed.
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 The study, published on Monday before peer-preview, said repeated
immunisation using inactivated vaccines such as the Sinopharm shot
as a fourth booster may not be ideal to further increase antibody
response against Omicron.
Certain protein-based vaccines or mRNA vaccines based on the genetic
information of variants of concern could be a good alternative for
further boost instead, according to the paper.
It remained unclear how the antibody readings may affect the three
or four-dose vaccine's effectiveness in lowering risk of
Omicron-caused COVID disease or death.
The study showed that neutralising 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.
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 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 study said a fourth dose, given 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.
The study, conducted by researchers at a
hospital affiliated with Sun Yat-sen University,
did not include readings among older people or
minors. It did not study the fourth dose's
impact on cellular immune response, which is a
different part of the human immune system than
the antibody-based response.
(Reporting by Roxanne Liu and Ryan Woo; Editing
by Miyoung Kim and Ed Osmond)
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