A Shanghai hospital conducts COVID-19 nucleic acid testing on its medical personnel on January 21, 2021 (photo: Yang Hui/GT)

Yongding hospital in Suzhou, East China's Jiangsu Province was closed from Sunday after the novel coronavirus was found on a door knob at the hospital on the same day, the local authority announced Monday. 

So far, 51 close contacts, including medical staff, workers and patients, have been tested and all returned negative nucleic acid test results. Their relatives and friends who live with them, 121 people in total, also tested negative for COVID-19.

What's more, 1,599 samples collected from all hospital staff, including medical staff, workers, and patients at the hospital, and their accompanying family members, returned negative nucleic acid test results. 21 environment samples from items like imported medical consumables, equipment and uniforms also tested negative.

The hospital, located in Wujiang district of Suzhou, is one of the city's designated places for administering COVID-19 vaccines, according to an announcement by Suzhou government on January 10. 

A Beijing-based immunologist, who requested anonymity, told the Global Times that it should first be investigated whether the positive sample was due to exposure to the COVID-19 vaccine. If the sample was contaminated by the vaccine, it would test positive to the novel coronavirus, he explained.

The expert noted that if the positive test was due to exposure from the COVID-19 vaccine, it would not be infectious; however, if it was from an infected patient or cold-chain product, there would be a risk of infection.