Doubts about the AstraZeneca vaccine: why some experts want it to stop

Although the WHO has already warned that herd immunity will not come in 2021, after the Pfizer / BioNTech and Moderna vaccine, there seems to be little missing even for AstraZeneca/Oxford, that should receive the green light on January 29 from the EMA.

The Anglo-Swedish vaccine, however, has sparked a series of doubts on the other side of the world, where a group of Australian scientists has called on the government to review its strategy immunization against Covid-19, concerned that the AstraZeneca vaccine is not effective enough to generate herd immunity.

Scientists have called for a pause on its large-scale spread as the country recorded a new Coronavirus outbreak on Wednesday, peaking in its most populous state of New South Wales. In Queensland, hundreds of guests at a quarantined hotel were forced to resume solitary confinement after cases related to the facility were recorded. English strain, considered highly viral, even among children.

How did Australia bend the contagion curve

However, Australia was more successful than many other countries in managing the pandemic, rising from a total of 25 million infections to around 28,600, with just 909 deaths.

Its success is largely attributable to closure of borders and al widespread compliance with the rules of social distancing, together with very strict testing and contact tracking programs. Just like China with its own “3 T system”.

However, several immunologists and the opposition Labor Party said Australia should seek additional supplies of Pfizer and Moderna vaccines, which studies show to be more effective. Some health experts also stand calling for a “pause” in the launch of the AstraZeneca vaccine next month. At the moment the proposal has been rejected by Canberra.

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“The government needs to be flexible in its launch decisions once we have a better understanding of the effectiveness of other vaccines,” said Adrian Esterman, president of Biostatistics and Epidemiology at the University of South Australia.

“The question is really whether it can provide herd immunity. We are playing a long game here. We don’t know how long it will take, ”said Professor Stephen Turner, president of the Australian and New Zealand Society for Immunology (ASI).

Australia’s vaccination strategy took a hit last month when a national vaccine candidate, developed by the University of Queensland and CSL, was abandoned after several trial participants returned false positives for HIV.

Plan B of Australia

The biggest Australian government order is with AstraZeneca. The Anglo-Swedish pharmaceutical company agreed to supply 53.8 million doses of his vaccine.

But Australia also ordered 10 million doses of the Pfizer vaccine because it had a contingency plan and agreed to agreements of AU $ 3.3 billion ($ 2.6 billion) with pharmaceutical companies for alternative vaccines.

Meanwhile, EMA, the European drug authority, has requested further information on issues related to the quality, safety and efficacy of the AstraZeneca vaccine.

Doubts about the AstraZeneca vaccine

I doubts of Australian scientists are mainly related to its effectiveness, on which uncertainties may still exist, and on the fact that it is different from rivals Pfizer and Moderna because it is not based on mRNA, but uses a different approach to induce the body’s immune response to the spike protein.

Specifically, it is a vaccine a viral vector which uses a modified version of the chimpanzee adenovirus, no longer able to replicate, as a vector to provide instructions for synthesizing the SARS-CoV-2 spike protein. Once produced, the protein can stimulate a specific immune response, both antibody and cellular. The technology is the same behind the first approved Ebola vaccine in late 2019, the only viral vector-based available to date.

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The peculiarity of this vaccine is also that it has demonstrated a ‘overall efficacy of 70.4% after two doses, but well of 90% for those who have taken half a dose at the first dose, and then a second full dose. Eventually, the effectiveness was declared at 95%, and 100% in the prevention of the most serious forms of Covid.

AstraZeneca CEO Pascal Soriot has clarified that the new data that will be published will show that the vaccine guarantees protection of 95% of patients, at the level of Pfizer and Moderna products, and is “100% effective” in preventing the most serious pathologies related to Coronavirus that would otherwise require hospitalization of the patient. “We believe we have found the winning formula to reach the effectiveness which, after 2 doses, is at the level of all the others. I cannot say more because we will publish the data ”.

Compared to the Pfizer vaccine, which requires a particular cold chain for storage and transport, the AstraZeneca-Oxford vaccine can be stored, transported and handled under normal refrigerated conditions (2-8 degrees centigrade) for at least 6 months and administered within existing health facilities. These elements will also affect the price of each individual dose.

Moderna and Pfizer’s vaccines, now widely administered in Britain, France, Israel and the US, have achieved over 90% efficacy. Probably high enough to force the virus out of circulation in the context of Australia, said Australian and New Zealand Society for Immunology President Stephen Turner.

The AstraZeneca vaccine “isn’t one I would distribute widely” because it has a lower efficacy rate than other options, Turner says.

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The Novavax vaccine

Commonwealth Chief Medical Officer Professor Kelly explained that the government was looking to get more doses from Pfizer because the company announced a deal to supply 12 million more doses to Malaysia and increase production to 2 billion. doses this year, with 600 million destined for the European Union and at least 200 million in the United States. The government is also in talks with a dozen companies to increase the supply of vaccines, but has not been able to get more doses from Pfizer or a first shipment from Moderna.

Asked if the pharmaceutical giant Johnson&Johnson unwilling to provide any of his vaccines to Australia, Kelly said “there were issues that we were unable to reach agreement on,” but said nothing more.

Australia currently does not use the so-called “mixed programs” on vaccines, but health authorities say there is evidence that this strategy can work. He may also decide to just inject the Novavax, Professor Kelly said, as Australia bought 51 million doses. But, at the moment, Novavax is stopped in clinical studies.


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