CanSino Biologics Inc's (CanSinoBIO) Covid-19 vaccine showed 74.8 per cent efficacy in preventing symptomatic cases and a 100pc success rate in stopping severe disease among Pakistanis in an interim analysis, Special Assistant to the Prime Minister (SAPM) on Health Dr Faisal Sultan said on Monday.

In the global trials, the efficacy of the vaccine at preventing symptomatic cases was 65.7pc and 90.98pc at preventing severe disease, he shared on Twitter.

The positive data moves the vaccine, jointly developed by a research institute affiliated with the Chinese military, a step closer to becoming China's third successful shot for the disease.

Although Covid-19 vaccines from Chinese developers have shown lower protection rates than some Western ones, and no detailed study results are publicly available yet, they have already been approved in several developing countries battling a surge in coronavirus infections.

The CanSinoBIO vaccine is being tested in Pakistan, Mexico, Russia, Argentina and Chile, according to clinical trial registration data, and the company has supply deals with some of those countries, including Mexico.

SAPM Sultan had said that Pakistan could receive “in the range of tens of millions” of the vaccine under an agreement with the Chinese firm. On another occasion he said the country is entitled to receive 20 million doses of CanSino's vaccine, "provided the results are positive and the vaccine proves to be effective".

In the Pakistani subset, efficacy at preventing symptomatic cases is 74.8% & 100% at preventing severe disease.

The IDMC didn't report any serious safety concerns. Data incld 30,000 participants & 101 virologically confmd COVID cases

Well done Pak team for conducting this trial

— Faisal Sultan (@fslsltn) February 8, 2021

Hassan Abbas, head of the CanSinoBIO trial at AJ Pharma in Pakistan, said it has already applied to the government for permission to import the vaccine.

“The initial set of vaccines will come in vials already filled, but we hope in the future to get them in the form of concentrates from CanSino, and do the filling here in Pakistan,” he told Reuters.

The efficacy of the shot is based on analysis of 30,000 participants and 101 confirmed cases of Covid-19, SAPM Sultan said on Twitter, quoting data from an independent data monitoring committee.

It was not immediately clear whether the study also looked into the vaccine's efficacy against new and highly transmissible variants first found in South Africa, Britain and Brazil.

No serious safety concerns have been raised in the study, Sultan said.

CanSinoBIO was not immediately available for comment.

Single-dose regimen

While the vaccine's protection rate trails the more than 90pc efficacy of shots developed by Pfizer Inc and its partner BioNTech SE and Moderna Inc, its single-dose regimen and normal refrigerator storage requirement could make it a favourable option for many countries.

CanSinoBIO's vaccine — which was approved for use in the Chinese military last year and has since been given to at least 40,000-50,000 people — uses a modified common cold virus known as adenovirus type-5 (Ad5) to carry genetic material from the coronavirus protein into the body.

However, researchers in an early and mid-stage trial report expressed concern the vaccine may not work in those previously exposed to Ad5, as the pre-existing antibody against the common cold virus could weaken the vaccine-triggered immune response.

CanSinoBIO is also testing a two-dose regimen of the vaccine in China including on participants aged between six and 17 and older than 55.

Shots from Chinese companies Sinovac and state-backed Sinopharm have shown efficacy of between 50pc and 91pc.

The three firms have applied to join the global vaccine sharing scheme Covax for approval and China plans to provide 10m doses to the initiative, which is backed by the World Health Organisation and GAVI vaccine alliance.