Working staff wear PPE at a neighborhood placed under lockdown, after a resident tested positive for COVID-19 in Shanghai on Tuesday Photo: VCG

The latest local coronavirus case reported at Shanghai Pudong International Airport on Tuesday was infected by the imported Delta variant after gene sequencing as the patient, an airport foreign cargo terminal staff member, was exposed to a COVID-19 contaminated environment, Wu Jinglei, director of Shanghai Health Commission said at a press conference held in Shanghai on Wednesday.

The Delta variant detected in the Shanghai case has no relation with the genome of latest domestic COVID-19 cases in Central China's Zhengzhou and East China's Nanjing, but it has high similarity with the imported Delta variant strain, according to Shanghai authorities.

As of 2 pm on Wednesday, a total of 67 close contacts of the latest COVID-19 patient have been put into quarantine and their two rounds of nucleic acid tests came back negative, Wu said.

Another 377 close contacts all took two nucleic acid tests and their results have come back negative so far.

So far 68,517 personnel have tested negative for nucleic acid tests, and 585 related environment samples all came back negative, Wu said.  

Shanghai escalated a residential compound in Pudong New Area to medium-risk after the city reported one new local coronavirus case on Tuesday, about six months since the city saw its last local infection. 

The patient hadn't left Shanghai 14 days before Monday, and his regular nucleic acid tests on July 21 and 28 both came back negative. He had no contact with imported cold-chain products, either. However, he performed high-risk activities such as unbuttoning protective clothing in a COVID-19 contaminated environment between July 22 and 23, according to Shanghai authorities.

The public worldwide has realized "the Delta variant strain spreads the virus much faster, with a higher viral load," Zhang Wenhong, China's leading infectious disease specialist said at the press conference.

The Delta variant strain has become the main virus around the world, so it's not surprising that the new wave in Nanjing, Zhengzhou, and the Shanghai case were all caused by the Delta strain despite having difference sources, Zhang noted.

However, a large scale of clinical research has proved that those countries with better vaccination performance will also perform well in combating the virus, according to Zhang.

Although there have been some COVID-19 infections reported in people who had already been vaccinated both at home and abroad, "the critical symptoms and death rate caused by the Delta strain have decreased dramatically," Zhang said, noting that "it's quite clear that vaccines are effective against the Delta variant strain." 

It has been recognized by global scientists, government officials and organizations that vaccines are one of the effective ways to prevent the spread of the pandemic.

As the protection is not 100 percent effective, "the only way is that we have to expand the scale of vaccination," Zhang said. Once the current vaccines become ineffective against the virus, vaccines corresponding to variants will be developed as well, Zhang noted.

With a resident population of over 24.87 million, Shanghai has administrated 38.2 million COVID-19 vaccine doses, involving 20.56 million people, including 18.80 million people who have fully completed the vaccine process as of Tuesday, Shanghai authorities said on Wednesday.