Chinese Sinovac Vaccine Shows Reduced Efficacy Against SARS-CoV2 Variant Identified In Brazil – But AstraZeneca’s Holds Up Well – Early Data
Healthcare worker in Chile opens up the Chinese-developed “CoronaVac” COVID-19 vaccine.

The Chinese-developed “CoronaVac” vaccine against COVID-19 vaccine triggers a sixfold reduction in neutralizing antibody response against the P.1 variant first identified in Brazil, according to a pre-print study published last week, while the Oxford/AstraZeneca vaccine is likely effective against the variant of concern. 

These findings come as hospitals in northern Brazil are increasingly overwhelmed and overcrowded; the country is reporting record high death rates; and the P.1 variant is becoming dominant in most of the country. 

The CoronaVac vaccine, produced by the Chinese pharma firm, Sinovac Biotech, is Brazil’s principal vaccine, with 120 million doses purchased by the government. CoronaVac accounts for over 70% of COVID-19 vaccines now being administered in Brazil. 

Some 10.83 million doses of COVID-19 vaccines have been administered in Brazil, but the virus continues to rage out of control, nearing record highs in daily cases, with 80,508 new cases reported on Sunday. With 2.68 million people fully vaccinated – 1.28% of the population – it could be too soon to draw conclusions about the efficacy of the vaccines in preventing transmission and infection in Brazil.

The new COVID-19 cases reported in Brazil. The country is reaching record high daily cases, with a seven day average of 66,869 new cases in March.

The P.1 variant was discovered in Manaus City in Brazil in early January and has several mutations – E484K, K417T, and N510Y – that are also present in the B.1.325 variant, which is circulating around the United Kingdom and South Africa and has been linked to higher transmissibility. 

The small-scale study of the CoronaVac vaccine, produced by the Chinese firm Sinovac Biotech, was conducted by researchers in Brazil, the United Kingdom, and the United States, found that the plasma from eight individuals vaccinated with Sinovac’s vaccine “failed to efficiently neutralize” the P.1 SARS-CoV2 variant. 

“Our data suggests that the SARS-CoV2 lineage P.1 can escape from neutralization antibodies elicited during infection or immunisation with previous circulating viral variants,” said the authors of the study. 

The neutralizing capacity in the blood plasma was six times lower against the P.1 variant compared to earlier lineages. According to the authors, the partial immunity against new variants could suggest that reinfection of previously infected or vaccinated individuals could occur. 

AstraZeneca’s Vaccine is Effective Against P.1 Variant, Says Preliminary Data

In contrast to Sinovac’s CoronaVac vaccine, early results from a study conducted at the University of Oxford indicate that the Oxford/AstraZeneca COVID-19 vaccine is effective against the P.1 variant. The results of the AstraZeneca study, which have not yet been made public, were shared with Reuters. The data indicates that the vaccine would not need to be modified to target the variant. 

This encouraging news follows the earlier release of data from a South Africa study, suggesting that the AstraZeneca vaccine was unable to protect people against mild and moderate cases of the B.1.351 variant of the SARS-CoV2, first detected in South Africa and bearing similarities to the P.1 variant. The full study will likely be released in March.

Sinovac Vaccine To Be Rolled Out Across Several Countries in Latin America and Asia
A second batch of 6.5 million doses of the Sinovac vaccine arriving in Turkey in late January.

Along with Brazil, mass vaccination drives of CoronaVac have begun in China, Indonesia, and Turkey and the vaccine has also been approved for emergency use in Colombia and Mexico. 

The efficacy rate of the vaccine against SARS-CoV2 was only 50.3%, based on late stage clinical trial results from Brazil. However, its developers claim that the vaccine is still 83.7% effective for more serious cases requiring medical treatment, and 100% effective in preventing hospitalisation. 

Sinovac previously said that the firm is looking into developing a vaccine for the variants or offering booster shots to extend protection. Both of these options could be developed fairly quickly, the company says.

“It’s like there’s this thief whom we’ve already caught,” said Yin Weidong, Sinovac’s CEO, in an interview with the Chinese government-controlled TV channel, CGTN, last week. “Even if it’s mutating, we can totally use the current research and production capacity to effectively develop a vaccine for the new variant.”

Risk Posed By P.1 Variant Extends To Other COVID Vaccines

Meanwhile, the P.1 variant, which has spread to more than 20 countries, poses potential risks to several other COVID-19 vaccines as well as possibly being more fatal. 

According to a pre-print study conducted by researchers at the University of São Paulo, Imperial College London, and the University of Oxford, the P.1 variant is between 1.4 and 2.2 times more transmissible than previous SARS-CoV2 lineages. 

The researchers estimate that P.1 evades 25% to 61% of protective immunity provided by infection from a different strain of the virus. 

“There was also evidence of an increase in mortality risk but whether this is due to P.1 or the extensive healthcare collapse Manaus has experienced remains uncertain,” said Thomas Mellan, a research associate at Imperial College London and co-author of the study, in a press release

“Uncertainty in the ways SARS-CoV2 is changing and implications for vaccine design calls for much more sequencing and analysis of virus genomes globally,” said Ester Sabino, professor of infectious diseases at the University of São Paulo and co-author of the study.

Image Credits: Twitter – Chinese Embassy Manila, Pontificia Universidad Católica de Chile, New York Times, Twitter – TRT World Now.

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