Study of the aggressive Covid-19 strain in Brazil suggests limits of the Chinese vaccine

Researchers from Brazil, the United Kingdom and the United States found that the plasma of eight people vaccinated five months ago with CoronaVac “failed to neutralize efficiently” the new Amazonian strain, called P.1. The study did not show whether CoronaVac can still prevent people from getting sick with the variant, one of the main goals of vaccination campaigns.

Although the sample size of the study is small and requires more testing, the fact that all eight samples produced the same result is a “notable phenomenon”, suggesting that CoronaVac is less able to prevent P.1 infections than the versions of the virus previously found in Brazil, said William de Souza, from the University of São Paulo in Ribeirão Prêto, one of the study’s authors.

Sinovac, the Chinese company that produces CoronaVac, did not respond to requests for comment. In an interview with state broadcaster CGTN that Sinovac launched this week, Chief Executive Yin Weidong said that, if necessary, it would take less time to develop a vaccine for the variants than from scratch.

“It’s like there’s a thief we’ve already caught,” he said. “Even if it is mutating, we can fully use current research and production capacity to effectively develop a vaccine for the new variant.”

Weidong said in the interview that Sinovac found that a person’s antibodies dropped half a year after vaccination with CoronaVac, adding that the company was still researching how long the protection would last and would release that data soon. He said the company is also evaluating the effectiveness of offering additional booster doses.

As the P.1 strain spread rapidly across Brazil and more than 20 other countries, concerns about how the existing Covid-19 vaccines will work against the variant and many others emerging in the largest country in Latin America have increased.

CoronaVac, which is expected to be implemented in much of Latin America and other developing countries in Africa and Asia, is Brazil’s best hope of overcoming the pandemic in the short term, public health experts said.

The disease has already killed more than 260,000 people in Brazil. While other countries around the world have left the worst of the pandemic behind, public health experts say Brazil is facing its darkest days, with its daily death toll expected to surpass that of the US and reach a new peak in the coming weeks. .

“This is going to be the biggest humanitarian tragedy in the history of Brazil,” warned Edinho Silva, the mayor of Araraquara, a city hard hit in the state of São Paulo, this week. A recent study showed that over 90% of Covid-19 patients in crowded hospitals in Araraquara tested positive for the P.1 strain.

The variant, which first appeared in the Amazonian city of Manaus at the end of last year, is 1.4 to 2.2 times more contagious than the versions of the virus previously found in Brazil and 25% to 61% more capable of reinfecting people, according to a recent study.

Its effects are already being felt across the country. Hospitals in most states have either run out of ICU beds or are operating at almost full capacity, while the scarcity of oxygen has recently led many patients to die from suffocation in the Amazon. Prosecutors investigated reports that intubated patients in the region were tied to their beds for lack of sedatives.

Public health experts said that Brazil now faces a race against time to vaccinate its population before other potentially aggressive new variants of Covid-19 emerge. The researchers estimate that there are already hundreds of strains of the disease circulating in the country, although P.1 is widely considered the most worrying.

After President Jair Bolsonaro spent months minimizing the pandemic and closing a vaccine supply deal with Pfizer Inc. last year, the country has relied heavily on CoronaVac since the start of its immunization campaign in January. The Chinese vaccine, developed in partnership with the state of São Paulo, accounts for more than 70% of the Covid-19 vaccines administered in Brazil.

Despite having an efficacy rate of around 50%, one of the lowest rates for any existing Covid-19 vaccine, CoronaVac has prevented 100% of moderate and severe cases of the disease, advanced clinical trials have shown in Brazil.

The P.1 study published on March 1, which also included researchers from the University of Oxford and the University of Washington School of Medicine, provides the first indications of how CoronaVac can respond to P.1.

However, infectious disease experts, including the study authors, have warned that further, broader studies would need to be carried out to show how well CoronaVac works against new variants and whether it can still prevent people from getting sick due to P.1.

The study itself was not designed to test CoronaVac specifically, but to test how antibodies created by vaccination or previous infections from other versions of Covid-19 respond when confronted with the new strain P.1.

“It is an exploratory study, a yellow light flashing, but not red,” said Carlos Fortaleza, an epidemiologist at Universidade Estadual Paulista, who did not participate in the study. “Preliminary results must be released very carefully,” he said.

Some scientists have expressed concern that such studies might dissuade people from getting vaccinated with CoronaVac, which has been heavily criticized by the president himself.

Bolsonaro, a fierce critic of China, told his supporters at the end of last year that CoronaVac could cause them to die or become disabled, without providing any evidence. Instead, he advocated the anti-malarial drug hydroxychloroquine and, more recently, the use of an experimental nasal spray to treat patients with Covid-19.

Public health experts largely blamed Bolsonaro’s government for the rising death toll in the country. Although many state governors have imposed restrictions on keeping Brazilians at home, the president encouraged people to break these rules and protested the masks.

“Stop complaining and complaining,” Bolsonaro, a brash former Army captain, said this week in what some experts said was also an attempt to divert media attention from a growing corruption scandal involving his son. “How long are you going to keep crying because of this?”

—Chao Deng in Taipei contributed to this article.

Write to Samantha Pearson at [email protected] and Luciana Magalhaes at [email protected]