Coronavirus: Nanjing cluster jumps to highest daily infections in China in months
- The Nanjing cluster – now at 106 cases – is the second most serious outbreak in China since February, with most cases Delta variant infections
- Molecular virologist suggests vulnerable and exposed populations be given a third booster dose of vaccine to save lives
The Jiangsu cluster is the second most serious outbreak in China since February, following 170 cases recorded in Guangdong in June.
“The number of cases reported has climbed recently,” deputy director general of the Nanjing Centre for Disease Control and Prevention Ding Jie said on Tuesday. “Early cases transmitted among aircraft cabin cleaners quickly and spread further through social activities and work environment contamination.
“We tracked down a large number of close contacts and have been testing them. New cases are constantly being discovered.”
“The Delta strain is more transmissible, more adapted to humans and faster to replicate. Patients have a higher viral load, take longer to treat and recover and are more prone to severe illness,” Ding said.
The city had launched a second round of mass testing while some high-risk areas had started their third, she added.
“We race against time with the virus, with measures to trace the source of the outbreak and contacts of patients, and manage close contacts and key groups. All measures have to be faster and stricter,” she said.
In addition to Jiangsu province, cases related to the cluster have been found in Guangdong, Liaoning, Anhui and Sichuan.
On Monday, Dalian in the northeastern province of Liaoning uncovered three asymptotic patients during Covid-19 testing required for air passengers who had been to Nanjing airport. Health authorities said the infected travellers were in transit at the airport for two hours on July 17.
The Delta variant has swept across more than 120 countries. It has been found to be more transmissible than previous variants and those infected need to have a higher level of antibodies to overcome it compared to the Alpha variant, according to the World Health Organization.
The variant was also quicker to reach a detectable level once a person was infected – all adding up to a much more transmissible strain, they said.
Jin Dong-yan, a molecular virologist at the University of Hong Kong, said there were no signs of superspreading of the virus in China yet, but people of higher risk – such as physicians and airport workers – should be given a third booster dose of vaccine.
The study, which has not been peer reviewed, showed that antibodies triggered by the Chinese vaccine declined below a key threshold from around six months after a second dose for most recipients, but a third shot had a strong booster effect.
“A third dose of CoronaVac administered six or more months after a second dose effectively recalled a specific immune response to Sars-CoV-2, resulting in a remarkable increase in antibody levels,” the researchers in China said.