It was developed by CanSino Biologics, with Phase III trials conducted in Argentina,[3] Chile,[4] Mexico,[5] Pakistan,[6] Russia,[7] and Saudi Arabia[8] with 40,000 participants.

[12] A Phase I study published in The Lancet showed two doses of a nebulised version of Convidecia (inhaled through the mouth) resulted in neutralising antibody responses similar to the existing one-dose injection.

[9] While the efficacy rates were lower than the Pfizer–BioNTech and Moderna vaccines, its single-dose regimen and normal refrigerator storage requirement (2 to 8 °C) could make it a favorable option for many countries.

[16] In May, Pakistan began filling and finishing 3 million doses a month at the National Institute of Health, which would be branded as PakVac for domestic distribution.

[28] In early 2020, Chen Wei led a joint team of the Institute of Biotechnology, the Academy of Military Medical Sciences, and CanSino Biologics to develop AD5-nCOV.

According to the Chinese state media, the team registered an experimental COVID-19 vaccine for Phase I trial in China on 17 March 2020, to test its safety.

[30] The Phase II trial results were published in the peer-reviewed journal The Lancet in August 2020, and noted neutralizing antibody and T cell responses based on statistical analyses of data involving 508 eligible participants.

[31] In September, Zeng Guang, chief scientist of the Chinese Center for Disease Control and Prevention, said the amount of COVID-19 antibodies in subjects from the Phase I trials remained high six months after the first shot.

Zeng said the high levels of antibodies suggested the shots may provide immunity for an extended period of time, although Phase III results were still required.

[36] In August 2020, the National Research Council disclosed the vaccine had not been approved by Chinese customs to ship to Canada, after which the collaboration between CanSino and the Canadian Center for Vaccinology was abandoned.

[37] In September 2020, CanSino began a Phase I trial in China with 144 adults to determine safety and immunogenicity when inhaled through the mouth with nebulizer rather than intramuscular injection,[38] with results published in 2021.

[42] In August 2020, Saudi Arabia confirmed it would begin Phase III trials on 5,000 people for Ad5-nCoV in the cities of Riyadh, Dammam, and Mecca.

[46][4] In December 2020, Argentina's Fundación Huésped began Phase III trials in 11 health centers in the metropolitan area of Buenos Aires and Mar del Plata.

[18] On 15 June 2021, Malaysia’s National Pharmaceutical Regulatory Agency (NPRA) has issued conditional registration for emergency use of the vaccine.

The COVID-19 Immunisation Task Force has prioritised the single-dose vaccine for communities living in remote areas including the Orang Asli as well as the homeless and undocumented individuals.