HomeLifestyleHealth & FitnessSinovac COVID-19 vaccine fades just SIX months after both doses

Sinovac COVID-19 vaccine fades just SIX months after both doses

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New research found that antibodies generated by Sinovac Biotech’s COVID-19 vaccine – formally known as CoronaVac – dropped below a critical level for the majority of patients around six months following the second dose. On the positive side, investigators discovered that a third dose had a significant booster effect.

The team of Chinese researchers published the results of a study including blood samples from healthy individuals aged 18-59 on Sunday, which has not been peer-reviewed.

Six months after receiving both Sinovac doses two or four weeks apart, only 16.9 percent and 35.2 percent of individuals, respectively, had neutralising antibodies beyond what researchers believe to be a detectable threshold level, the study said.

These statistics are based on data from two cohorts, each of which had more than 50 individuals, and a total of 540 people received third doses of either the vaccine or a placebo.

Researchers were unable to determine how the reduction in antibodies would affect the shot’s efficacy since scientists have yet to determine the precise antibody level required to prevent COVID-19.

The study, titled Immunogenicity and safety of a third dose, and immune persistence of CoronaVac vaccine in healthy adults aged 18-59 years, concluded:

“In the short-to-medium term, ensuring more people complete the current two-dose schedule of CoronaVac should be the priority.”

Indonesia and Thailand have both agreed to offer a third jab from Moderna and Pfizer respectively for some people who are fully vaccinated with the Sinovac vaccine in the face of concerns over how effective it will be against the Delta variant, which is considerably more infectious than the original strain.

Turkey had also begun giving a third dose of Sinovac or Pfizer to certain individuals who have had Sinovac injections.

Sinovac has distributed over one billion doses of the vaccine as of the end of last month, not just in China, but also in other major nations such as Brazil, Indonesia, and Chile.

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

Additionally, the research said that individuals in some cohorts who got a third Sinovac injection around six months after the second exhibited a three- to fivefold rise in antibody levels after an additional 28 days, compared to levels observed four weeks after the second shot.

The researchers stressed that the trial did not evaluate the antibodies’ efficacy against more transmissible variations and further research is needed to assess antibody duration after a third injection.

The investigation was performed by researchers from Jiangsu province’s disease control authority, Sinovac, and other Chinese organisations.

Separately, research released by Thailand’s Centre of Excellence in Clinical Virology at Chulalongkorn University’s Faculty of Medicine indicated that a combination of Sinovac and AstraZeneca – the vaccine produced in collaboration with Oxford University – may be ” highly effective”.

The study found two doses of Sinovac, which makes use of what is known as the inactivated virus method, can help “immunity rise to an average level of 100 units”.

In addition, if two doses of AstraZeneca, which makes use of a new technique known as the vector method, are administered, the immune system shoots up to 900 units, the study claims.

Dr Yong Poovorawan, the director of the centre, told the Phuket Times he was conducting “in-depth” research into its ability to block each variant of the virus.

Nevertheless, the World Health Organization (WHO) does not currently recommend the use of vaccine “cocktails” in this way.

Photo by Samsul Said/Bloomberg via Getty Images

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