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A health care worker receives the Johnson & Johnson Covid-19 vaccine in Cape Town, South Africa, on February 17. The vaccine has been approved by South African Health Products Authority and is expected to only be given to health care workers. Photo: EPA-EFE

Coronavirus: Sinovac claims good results against British and South African strains challenging vaccine makers

  • Vaccine makers prepare to develop improved booster shots to stay on top of emerging variants
  • Sinovac CEO says inactivated vaccines offer a broad spectrum of protection but the company did not show data backing its claim
The emergence of a more contagious strain of the coronavirus first discovered in South Africa has kept vaccine developers around the world on their toes for fear it might impair protection offered by their products.

The developers are testing how the variant, known as B.1.351, is affecting the immunisation power induced by their vaccines and preparing to update their booster shot.

On Wednesday, Sinovac’s partner in Brazil said its Covid-19 vaccine worked well against the coronavirus variants first found in Britain and South Africa but did not provide further details.

“We have tested this vaccine in China against the English and the South African variants, with good results,” Dimas Covas, head of the Butantan Institute which tested and makes Sinovac’s vaccine in Brazil, told Reuters.

Covas did not elaborate on how well the vaccine, called CoronaVac, worked on the variants or show data to support such a conclusion.

Last month, Yin Weidong, Sinovac Biotech CEO, told state news agency Xinhua he believed inactivated vaccines that stopped the coronavirus from replicating had a broader spectrum of protection against different mutations of the coronavirus. CoronaVac uses inactivated vaccine technology.

Although the coronavirus was expected to mutate, researchers have been concerned about how some mutations will affect vaccines.

One mutation, known as E484K and found in different variants first detected in South Africa (B.1.351), Brazil (B.1.1.28) and recently in some patients carrying the UK B1.1.7 variant, is particularly worrying after researchers found it could greatly reduce the potency of some vaccines.

Early clinical trial data showed vaccines from Novavax and Johnson & Johnson had much less efficacy in trial participants in South Africa, where the B.1.351 variant was widespread, compared with countries where the variant was less common. South Africa stopped its Oxford-AstraZeneca vaccine programme after preliminary data showed it failed to protect against mild and moderate forms of Covid-19 caused by the B.1.351 strain.

Why more contagious Covid-19 variants are emerging

Vaccine developers around the world are testing how their products respond to the emerging variants and some have prepared for possible updates of their vaccines.

Earlier this month, Chinese researchers tested how two vaccines responded to the B.1.351 variant and found both products “largely preserved neutralising titres with slightly reduction” in a small-scale lab study. One inactivated vaccine was developed by a subsidiary of China National Pharmaceutical Group and is already approved for general use with conditions in China. The other is a protein subunit vaccine developed by the Chinese Academy of Sciences and is in phase 3 human trials.

Researchers used 12 serum samples from people vaccinated with either of the two products to neutralise real virus strain, isolated on January 6 from a South African airline pilot, and found the neutralising antibodies declined 1.6-fold, suggesting the B.1.351 variant did not escape the immunity induced by the two vaccines, according to a paper was published on preprint server platform bioRxiv.org. The paper was not peer reviewed.

On Wednesday, a laboratory study by scientists from Pfizer-BioNTech and the University of Texas Medical Branch and published in the New England Journal of Medicine showed blood drawn from vaccinated people was two-thirds weaker when neutralising an engineered virus with the same mutations in the spike protein as in the B.1.351 variant.

Canada researchers urge delay in administering Pfizer jab’s second dose

However, it is not clear whether or how the two-thirds reduction would affect real-world protection by the vaccine. In human trials, one dose of Pfizer-BioNTech already offered protection before the development of high neutralising titres. The lab study only looked at one aspect of immune response, the neutralising antibodies, whereas vaccines could generate other types of antibodies and cells too.

Pfizer and BioNTech said they were talking to regulators to develop and seek authorisation for an updated version of the vaccine or booster dose once a strain that significantly reduced the vaccine’s protection was identified.

Separately, researchers from another mRNA vaccine developer, Moderna and the National Institutes of Health, said in a paper published in the same journal that they observed a decrease in titres of neutralising antibodies against the B.1.351 variant in a pseudovirus-based model and protection against the variant “remains to be determined”.

Moderna is preparing for a clinical trial of a booster dose to combat the new variants.

This article appeared in the South China Morning Post print edition as: Drug firms scramble to tackle new strains of virus
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