China-Pakistan bonhomie has suffered a serious setback after the Beijing failed to find volunteers for its Phase 3 clinical trial of a new Covid-19 vaccine.

Two months after China's closest ally approved the final phase of clinical trials for Ad5-nCoV, barely 500 candidates have signed up for testing. In exchange for offering test subjects, China was to supply the vaccine to Pakistan as priority.

Nikkei Asia cited Pakistan government-run research body National Institute of Health as saying, "Hospitals have been facing difficulties in recruiting volunteers for the trials because of the flood of misinformation, mainly on social media."

The Nikkei report also cited a survey conducted in October by Gallup Pakistan which showed that 55% of Pakistanis were unsure if the virus is real and that 46% considered it part of a conspiracy.

Regardless, Islamabad is trying to make amends with Beijing. 

On Tuesday, the government published front-page advertisements in newspapers urging people to volunteer for the trial.

Ad5-nCoV has been co-developed by CanSino Biologics, a Tianjin-based Chinese vaccine company, and Chinese military-backed research arm Academy of Military Medical Sciences.

The Ad5-nCoV vaccine candidate has been developed using a weakened version of adenovirus (a common cold-causing virus).

Trials have so far shown that a single dose of the Ad5-nCoV produced virus-specific antibodies and T cells in 14 days, making it a potential candidate for further investigation.

CanSino Biologics is slated to conclude phase III trials of its vaccine candidate in January 2022.