Five fully vaccinated workers tested positive for COVID-19 at Shanghai International Airport in China on Saturday, according to the municipal government.
It came as China’s top epidemiologist, Zhong Nanshan, stated that vaccine effectiveness against the variant diminishes six months after the first dose.
On Friday, the city’s Pudong International Airport recorded two cases, one involving a Chinese national and the other an Ethiopian national, both in their 40s. Authorities quickly sealed off the two neighborhoods.
Local authorities then conducted overnight testing in an attempt to halt the new outbreak, and three more cases were discovered on Saturday. According to online postings, some residents were awakened at 3 a.m. to perform nucleic acid testing.
The five are cargo workers at the city’s airport, and their case follows that of a nurse from a nearby hospital who tested positive on Wednesday despite being fully vaccinated.
All of these cases came from vaccination priority groups.
Since late July, the highly transmissible Delta variant has been detected in more than a dozen Chinese cities.
Because of the spread of the latest strain of the CCP (Chinese Communist Party) virus, the busiest Chinese airport by freight volume has suspended all cargo traffic since Friday afternoon, including international freight and cargo loading and unloading.
By Saturday morning, Shanghai had tested tens of thousands of its residents, including the five airport workers’ close and secondary contacts.
China’s top epidemiologist, Zhong Nanshan, said on Friday that the effectiveness of vaccines against the variants, including those made in China, such as Sinovac, had declined after half a year.
He denied that the first shots had failed, but suggested that a third dose would be required to boost immunity.
Zhong claimed in early August that Chinese vaccines provide 100 percent protection against deaths and intensive care admissions.
Countries that vaccinated more than half of their populations, largely with China-made vaccines, did not see the hoped-for reduction in new infections. Chile, which relies on Chinese vaccines, announced on August 5 that it would provide booster shots to recipients of the Sinovac vaccine.
According to local studies, the vaccine is less effective than Pfizer and AstraZeneca and has a lower efficiency in preventing symptomatic illness months after inoculation.
China has not confirmed whether foreign vaccines will be administered as booster shots to its fully vaccinated population.
According to the National Health Commission, the national total of new confirmed cases on Saturday was 32. China also reported 19 new asymptomatic CCP virus cases that were not confirmed infections.