Coronavirus: Odds of 50-50 are enough for a jab

Pharmaceutical giant AstraZeneca has revealed it is aiming to produce a vaccine with 50 per cent effectiveness.

Scott Morrison and Acting Chief Medical Officer Paul Kelly at Sydney’s AstraZeneca lab last month. Picture: Getty Images

Pharmaceutical giant AstraZeneca — which is manufacturing Oxford University’s Covishield candidate — has revealed it is aiming to produce a vaccine with 50 per cent effectiveness.

As AstraZeneca released its vaccine trial blueprint, the pharmaceutical company continued to face questions over vaccine safety and the timeliness of its disclosure that two trial participants in Britain were suspected of suffering adverse reactions.

The manufacturers of COVID-19 vaccines in development around the world have been under pressure to release their vaccine protocols — documents that are usually jealously guarded on confidentiality grounds. US biotech Moderna and global pharmaceutical company Pfizer both published their COVID-19 vaccine blueprints late last week.

AstraZeneca said in its published protocol for the Covishield vaccine that a vaccine with 50 per cent effectiveness would be considered to have met its endpoint goal. The company would determine that it had met that target once at least 150 people who received either a vaccine jab or a placebo shot had been confirmed to have coronavirus.

In total, 30,000 volunteers would be involved in the clinical trial.

The phase three Covishield vaccine trial has been resumed in Britain after being suspended following suspected adverse events, but regulators in the US have not yet allowed the trial to resume.

The AstraZeneca protocol also lays out the trigger points for analysis to take place which would potentially result in emergency doses of the vaccine being made widely available, subject to regulatory approval. The protocol envisages a safety board analysis after 75 confirmed coronavirus cases had been observed in those who received a vaccine or placebo. If a 50 per cent effectiveness rate was achieved among those 75 cases, the company proposes it may apply to regulators for approval for emergency dosing.

The Morrison government has signed a $1.7bn production and supply deal with pharmaceutical company CSL to manufacture two potential COVID-19 vaccines — the Covishield vaccine and the University of Queensland’s candidate.

The deal would see CSL produce 80 million doses of the two vaccines, which includes 30 million doses of Covishield.

The deal is intended to cover two doses of vaccine for every Australian as well as some coverage across the Pacific and Southeast Asia.

However, the Oxford University vaccine is far from a sure bet. Phase three trials in the UK were halted this month after a female participant in the study developed neurological symptoms including changed sensation and limb weakness. The case was the second instance of reported neurological symptoms among trial participants.

A safety review found the illnesses were “considered unlikely to be associated with the vaccine or there was insufficient evidence to say for certain that the illnesses were or were not related to the vaccine”.