A handover ceremony is held for the second batch of COVID-19 vaccines donated by the Chinese government at Noor Khan Air Base near Islamabad, capital of Pakistan, March 17, 2021.(Photo: Xinhua)

Pakistani President and officials defended China's Sinopharm vaccine amid some doubt over the vaccine's efficacy after Prime Minister Imran Khan, who received a shot on Thursday, tested positive for COVID-19 two days later. 

Chinese experts backed Pakistani officials, saying Khan must have contracted the virus before vaccination, and that vaccines cannot be effective in such a short time after inoculation.

Khan's office confirmed the prime minister tested positive for COVID-19 on Saturday and has since self-isolated, two days after his first jab with the Sinopharm vaccine. Khan's infection raised questions over Chinese vaccines' effectiveness, which Pakistan health authorities and officials rebutted by listing the facts of Khan's infection. 

"Prime Minister Imran Khan was not fully vaccinated when he contracted the virus. He only got the first dose and merely two days ago which is too soon for ANY vaccine to become effective," the country's Ministry of National Health Services, Regulations and Coordination wrote in a statement on Saturday, shrugging off the rumors. It added that anti-bodies develop two-three weeks after the second dose of two-dose COVID-19 vaccines.

Arif Alvi, president of Pakistan, also voiced confidence in Chinese vaccines.  

"COVID-19 vaccination is a must. It is given in two doses [and] takes a few weeks to become effective. In most cases it is 100% effective [and] in remaining, severity of infection is greatly reduced which increases survival rate," the president wrote on Twitter on Sunday. 

"Beware of those who create doubt, as they know not," Alvi warned his people regarding vaccine stigmatization. 

Alvi and his wife received Sinopharm vaccine shots on March 15. 

Asad Umar, chairman of the country's National Command and Operation Center (NCOC), said that Khan, 68, was vaccinated on Thursday evening and felt some signs of the disease on the next day, so "obviously he was infected before being vaccinated" because COVID-19 symptoms take a few days to manifest, the Xinhua News Agency reported.  

Chinese vaccine experts backed Umar's assertion. "It is safe to say that the PM's infection predated the vaccination and was a completely independent event," Tao Lina, a Shanghai-based vaccine expert told the Global Times on Sunday.

"The vaccine that Khan received is an inactivated vaccine and is not effective against an already infected organism," Tao said. "As of now, all of the listed COVID-19 vaccines lack sufficient clinical data to prove they can produce a blockade in those already infected."

Even assuming he was infected after the vaccination, it does not indicate that the vaccine was not effective enough, Tao said. 

"The vaccine could not have possibly developed a protective effect on the prime minister in two days, as current clinical data shows the vaccine takes a week or longer to become effective, depending on the individual recipient." Tao added that mass vaccination should continue to be promoted. 

Pakistan has seen a sharp rise in COVID-19 cases in the past few weeks. According to figures released by the Ministry of National Health Services on Sunday, the country registered 3,667 COVID-19 infections in the past 24 hours, bringing the total to 626,802. 

Currently, Sinopharm is the only vaccine available in the country. Pakistan received another 500,000 doses of Sinopharm vaccine on Wednesday, after the first batch of half a million sent from China arrived on February 1.