Many countries from China to Indonesia and Brazil rely heavily on Chinese vaccines to inoculate their populations against COVID-19, but there are growing concerns about whether they provide enough protection against the Delta variant of SARS-CoV-2, first identified in India.
Below are views from China’s health experts about the effectiveness of home-grown vaccines against the virus strain, which is becoming the globally dominant variant, and the preventive measures China is taking.
Do Chinese vaccines work against the strain?
Photo: EPA-EFE
China has not provided vaccine effectiveness results against the variant based on large-scale data in clinical trials or real-world use, nor offered detailed information from lab tests, but Chinese experts are urging people to get inoculated as soon as possible.
The lack of detailed data on the Chinese vaccines against the variant has hobbled any meaningful peer reviews by foreign experts.
Researchers found that Chinese vaccines are somewhat effective in reducing the risk of symptomatic and severe cases caused by the Delta variant, said Zhong Nanshan (鍾南山), an epidemiologist who helped shape China’s COVID-19 response.
Their findings are based on analysis of infections in Guangzho, China.
Zhong said the results are preliminary and the sample size is small.
Preliminary results based on blood samples from those vaccinated with its shot showed a three-fold reduction in neutralizing effect against the variant, Sinovac spokesman Liu Peicheng (劉培成) said.
He said a booster shot following the two dose-based regimen could quickly elicit a more durable antibody reaction against the strain, but he did not provide detailed data.
Antibodies triggered by two Chinese vaccines are less effective against the Delta variant than other strains, Feng Zijian (馮子健), former deputy director at the Chinese Center for Disease Control and Prevention, told state media last week.
Feng did not provide details, including the names of the vaccines.
The shots could still offer protection, as none of those vaccinated in Guangdong Province, where China’s first cases of the Delta variant were found, developed severe symptoms.
Jin Dong-Yan (金冬雁), a virologist at the University of Hong Kong, said Feng’s comment alone is not enough to back up the claim that Chinese vaccines are effective against severe cases, as more data are needed.
Indonesia, which has reported record daily cases recently due to a surge in the variant, saw hundreds of medical workers infected by the COVID-19, despite being vaccinated with Sinovac’s shot, officials said earlier this month.
However, it was not clear if the Indonesian medical workers were infected by the Delta variant.
How do they compare with other shots?
A study by Public Health England (PHE) last month found that the Pfizer-BioNTech vaccine was 88 percent effective against symptomatic disease from the Delta variant two weeks after the second dose.
That compared with 93 percent effectiveness against the Alpha variant, first identified in the UK.
Two doses of the AstraZeneca vaccine were 60 percent effective against symptomatic disease from the Delta variant, compared with 66 percent effectiveness against the Alpha variant, PHE said.
There is no substantial data showing how protective Johnson & Johnson’s single-dose COVID-19 vaccine is, and US infectious disease experts are weighing the need for booster shots using messenger ribonucleic acid vaccines.
How severe was the Guangdong outbreak?
Guangdong became China’s biggest cluster of Delta cases since reporting its first locally transmitted Delta variant infection last month.
The infections included 146 cases in Guangdong’s capital, Guangzhou, and several cases from Shenzhen and nearby Dongguan.
No new domestic transmissions of any variant have been reported in the province since Tuesday last week.
What did China do?
Guangdong, which has 126 million people, has fast-tracked its vaccination effort since the outbreak. It had administered just 39.15 million doses as of May 19, but the number shot up to 101.12 million by June 20.
Guangzhou, Shenzhen and Dongguan quickly sealed off neighborhoods where those who were infected and their contacts visited, and launched multiple rounds of mass testing, following the protocols observed during previous outbreaks.
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