Antibodies from Sinovac’s COVID-19 vaccine fade after 6 months, study finds

pharmafile | July 27, 2021 | News story | Manufacturing and Production, Medical Communications, Research and Development, Sales and Marketing  

A Chinese laboratory study has found that antibodies from Sinovac Biotech’s COVID-19 vaccine drop below a key threshold around six months after a second dose for most recipients, with the company having already delivered over 1 billion doses of the jab.

Researchers reported the findings from a study of blood samples from healthy adults aged between 18-59 in a paper published on Sunday, which has not been peer reviewed.

Participants received two doses of the jab, two or four weeks apart, and only 16.9% and 35.2% respectively still had neutralising antibodies above what researchers regard as a detectable threshold level six months after the second shot.

These data were taken from two cohorts involving more than 50 participants each, with a third cohort being given a third boaster dose or placebo, to a total of 540 participants.

The study’s researchers have stated that people in some cohorts who received a third dose of the Sinovac shot about six months after the second showed around a 3-5 fold increase in antibody levels after a further 28 days, compared with the levels seen four weeks after the second shot.

The researcher stated in the paper that “In the short-to-medium term, ensuring more people complete the current two-dose schedule of CoronaVac should be the priority”, and also went on to say that the data does not reflect efficacy rates against new variants of concern.

Indonesia and Thailand have already agreed to give a third shot from Moderna and Pfizer respectively for some people who are fully vaccinated with the Sinovac vaccine, amid concerns over its effectiveness against the more transmissible Delta variant of the coronavirus.

Turkey had started offering a third dose from either Sinovac or Pfizer to some people who have got Sinovac shots.

Philippines’ Health Secretary Francisco Duque said on Tuesday there is no recommendation yet from the country’s vaccine expert panel on giving a booster shot but experts are discussing the possibility.

The study was conducted by researchers at disease control authorities in Jiangsu province, Sinovac, and other Chinese institutions.

Kat Jenkins

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