Questions raised ahead of Australia’s rollout of Oxford-AstraZeneca vaccine

The rapid development and rollout of COVID-19 vaccine promises much in terms of liberating the world from the pandemic and restoring normality to travel, trade and everyday life.

However, not all vaccines are equal and much is still not known regarding their effectiveness when rolled out to the broader public compared with clinical trials.

This week concerns were raised in Australia over the capability of the British-developed Oxford-AstraZeneca vaccine, upon which the country has staked its hopes to the tune of 53.8 million doses, most of which will be manufactured locally.

Last year leading medical journal, The Lancet, reported the efficacy for the Oxford-AstraZeneca COVID-19 vaccine was 62.1 percent with two standard doses of the vaccine.

On Wednesday, several media outlets reported that the Australian and New Zealand Society for Immunology (ASI) was calling for a pause to the government’s rollout of the vaccine, over concerns that it may lack the effectiveness to offer herd immunity.

Australian Chief Health Officer Paul Kelly swiftly defended the decision to deliver the vaccine to Australians, fearing the potential for an undermining of public confidence regarding safety.

“People should be confident about safety, being our first priority,” Kelly said. “By using this vaccine, we’ll be able to protect a large proportion of the population in Australia.”

ASI later clarified that it was not calling for a pause to the rollout and that comments given by one of its members were from an immunology perspective rather than being directed at policy.

“The intention was to highlight that the Oxford-AstraZeneca vaccine has a beneficial role to play in what is a multi-pronged approach to combating the impact of the COVID-19 pandemic,” ASI said in a statement.

“The current position is that ASI does not advocate a pause on the rollout of the Oxford-AstraZeneca Vaccine.”

Crucially, the AstraZeneca vaccine is just one of the four the Australian government has entered into agreements to secure.

Plans were also in place to vaccinate high-priority groups such as frontline health workers with the Pfizer-BioNTech vaccine as early as February, pending approval by Australia’s regulator, the Therapeutic Goods Administration (TGA).

The Pfizer vaccine is believed to be around 90 percent effective in stopping symptomatic disease, with some experts suggesting Australia should wait until more doses become available rather than proceeding with the AstraZeneca.

Epidemiologist and Chair of Biostatistics at the University of South Australia Prof. Adrian Esterman pointed out that with Australia’s relatively low case rates there was less urgency in delivering a vaccine to the broader population.

“In other countries where the epidemic is rampant, an efficacy of 60 percent would still be very helpful in dampening down transmission and providing relief to the hospital services.

“However, Australia is luckily not in that position, and there is a strong argument for vaccinating as soon as possible the at-risk population with two doses of the Pfizer-BioNtech vaccine, and holding off for the rest of the population until more doses of it are available.”

Esterman added that the actual effectiveness of the AstraZeneca was not yet known and that it might have much higher efficacy than reported in the interim results.

Part of the issue involved with determining the effectiveness of vaccines is that results may vary from those of smaller clinical groups compared to the broader population. Clinical groups are hand selected and generally do not involve people with wildly varying circumstances and health conditions as within the community at large.

“Basically, the efficacy achieved for one cohort of individuals cannot be extrapolated to under-evaluated ages or other populations and so further bridging trials are required,” Senior lecturer at the Australian Catholic University Faculty of Health Sciences, Dr. Roger Lord said.

Lord pointed out that while the AstraZeneca vaccine may yield a lower effectiveness rate, it also does not require ultra-low temperature freezers for storage and is cheaper than the Pfizer and Moderna vaccines, on top of showing no serious adverse events or deaths with use.

“Vaccine efficacy is important but so is community acceptance, logistics of delivery, length of protection, safety and economic feasibility,” Lord said.

Expert consensus supported the Australian government going ahead with delivering the AstraZeneca vaccine to the public while remaining flexible to updates regarding vaccine effectiveness and availability.

For the time being Australia will continue with the manufacturing and planned roll out of the AstraZeneca vaccine, largely because that is what is available and practical at the time.

“The choice is not whether one is better than the other, it’s which one is available to give the maximum rollout of vaccine … to protect lives this year,” Kelly said.