Employees of Shanghai Pudong International Airport take nucleic acid tests on August 20, 2021. Photo: CFP

Five new local COVID-19 infections reported at Shanghai airport's international cargo flight zone on Friday and Saturday suggest the necessity of antibody detection among frontline workers, expert noted in response to public concerns over increasing cases of vaccinated people who are getting infected. 

Shanghai reported three new local COVID-19 infections on Saturday following screening nucleic acid testing on close contacts of the two cases reported in the city on Friday. 

All the five cases reported over the past two days work at Shanghai Pudong International Airport with their work related to international cargo flights. 

The five patients are men aged between 44 and 45, including an Ethiopian mechanical engineer and four Chinese airport staffers working on international cargo flights at the Pudong airport. It is noteworthy that all of them have completed their two doses of vaccine inoculations. 

A Beijing-based immunologist told the Global Times on Sunday that these cases suggest the potential risks international flights pose on the domestic epidemic control. 

The immunologist noted that a post-vaccination policy should be considered including antibody detection among the frontline workers as all the infected individuals already received two doses of vaccines. Although the rate of inoculation among frontline workers is already very high, people's reaction toward the vaccines differs, he noted. 

According to Shanghai Municipal Health Commission, all the five cases have been transferred to the Shanghai Public Health Clinical Center for quarantine and treatment. 

Three residential compounds and a hotel in Pudong New Area where the five infected individuals live were locked down and elevated to medium-risk areas apart from a compound in Songjiang district, where an infected nurse lives. The source of the infection hasn't been established yet. 

Since the end of 2020, the international cargo flight zone of Pudong airport has reported sporadic COVID-19 cases for four times with 3 patients confirmed as of Saturday. All these infections are international cargo related workers and their relatives or couriers working at the cargo zone. 

The first case of this round of outbreak at the airport confirmed on August 2 was discharged from hospital on Friday. 

Affected by the epidemic, the entire cargo zone of the Pudong airport has been closed since Friday morning and all the cargo flights have been suspended. 

Wang Xiaojie, deputy director of Shanghai Municipal Transportation Commission, assured the public during a press briefing on Saturday that the Pudong airport has stuck to the contagion control protocol which strictly separates passenger and cargo flights as well as international and domestic flights. All the personnel, items and environment are under closed-loop management. Passenger flights are operating normally. 

International cargo or passenger flights have become the major sources of local infections in the recent outbreaks of domestic resurgences. 

Cleaners work on a COVID-19-polluted Russian passenger flight got infected and started a chain of events leading to the outbreak at the Nanjing Lukou International Airport in East China's Jiangsu Province which eventually spread to other provinces. 

Other international cargo flights-related local infections included the cases reported from the airports in Haikou in South China's Hainan Province and in Xiamen, East China's Fujian Province.