May 8, 2024

expert reaction to AstraZeneca withdrawing its Covid-19 vaccine

Scientists react to AstraZeneca withdrawing its Covid-19 vaccine. 

Prof Adam Finn, Professor of Paediatrics, University of Bristol, said:

“Global demand for all COVID vaccines is now much lower and overall supply exceeds demand. This is in marked contrast to the early part of the pandemic when supply was limited and distribution very limited, especially in poorer countries.

“The AZ-Oxford vaccine which expresses the original Wuhan Spike protein, and has not been updated, is probably now much less effective than it was to begin with because the Spike protein on the SARS CoV2 variants now circulating has changed a good deal over time as the virus has evolved away from the immunity people have gained from vaccination and infection.

“Accordingly, there is probably no commercial case for continuing to manufacture and distribute the vaccine and I think this is likely to be the main reason the company have decided to discontinue making and selling it.

“Although there were cases of TTS caused by this vaccine and the ADV-vector COVID19 vaccine made by Johnson and Johnson (Janssen), including deaths, the main current issue related to that problem is that we need to understand more fully the mechanism by which it occurred in order to avoid any risk of something similar happening with other vaccines in the future.

“This vaccine saved very large numbers of lives in many countries around the world particularly in 2021 and 2022, both because it was developed and tested so rapidly and because AZ made it available at very low cost so that it could be used in many of the poorer countries in the world.”

Prof Peter Openshaw, Professor of Experimental Medicine, Imperial College London, said:

“The Oxford/AZ adenovirus-based vaccine was designed for rapid global deployment and was the lest expensive of all the vaccines that were available in the early stages of the pandemic, coming in at only $4-8 dollars a shot. This meant that it had a huge global reach, 100 million doses being commissioned by the UK Vaccine Taskforce in July 2020. This overshadowed the mRNA vaccines from BioNTech/Pfizer and Moderna vaccines (90 and 17 million doses respectively at that time). The mRNA vaccines cost between $20 and $30 per shot and needed a full cold chain, making them unavailable in resource-poor setting.

“An assessment published in The Economist in July 2022 based on data from Airfinity showed that both the Oxford/AZ and Pfizer-BioNTech vaccines had most likely prevented around 6 million premature deaths each. Airfinity also showed that the Oxford/AZ vaccine was by far the most often used vaccine outside the EU, UK and USA (presumably because of cost, ease of manufacture and stability during transport).

“The lives saved by these highly effective vaccines have to be balanced against the rare but potentially serious side effects, specifically vaccine-induced thrombocytopenia and thrombosis (VITT) that was reported in about one in 500,000 Oxford/AZ vaccine recipients. Such rare side effects are usually inapparent until late in vaccine rollout, but may lead to suspension or withdrawal of vaccines. There was a UK government-backed scheme that compensated those who were affected by adverse effects of vaccines.

“In the face of alternative vaccines that can be rapidly updated and do not have this unexplained and unexpected effect, the decision to cease issuing this type of vaccine is logical. However, the vast contribution that the Oxford/AZ vaccine made to global protection against COVID should not be forgotten.”

Prof Jonathan Ball, Deputy Director of Liverpool School of Tropical Medicine and Professor of Molecular Virology, Liverpool School of Tropical Medicine (LSTM), said:

“We seem to forget how desperate the global population were for an effective COVID-19 vaccine, and the AZ vaccine saved millions of lives. However, there were relatively early indications that the vaccine was associated with very rare, but very serious complications, and eventually other vaccines, particularly those capable of giving protection against newly emerging variants of concern have come to the fore. 

“With almost everything we do there is a harm-benefit assessment that we have to make, and at the peak of the pandemic the AZ vaccine brought far more benefit than harm – that would still be the case, but now more effective and safer avenues are available.”

Professor Lawrence S. Young, Virologist and Professor of Molecular Oncology, Warwick Medical School, University of Warwick, said:

“It’s important to get some perspective on this decision. The Oxford/AZ vaccine saved millions of lives. It was produced at a time when we knew little about the SARS-CoV-2 virus and were in desperate need of a vaccine to prevent severe disease. This vaccine was crucial to the global fight against COVID-19. 

“Updating this vaccine technology to cover new covid virus variants is difficult compared to mRNA vaccines which can be more rapidly modified. As the covid virus continues to mutate, the mRNA vaccine platform offers more flexibility. The decision to withdraw the AZ vaccine is probably mainly due to the cost and complexities of generating updated vaccines to new virus variants. The rare but serious thrombotic side effects of the vaccine must also have been a consideration.”

Dr Michael Head, Senior Research Fellow in Global Health, University of Southampton, said:

“It has been an excellent and vital vaccine, a key part of the pandemic response for most countries around the world. There would have been far more deaths, hospitalisations, illness and transmission, if we hadn’t had the AstraZeneca vaccine, alongside the other key vaccines such as Pfizer and Moderna.

“For example, during the humanitarian crises in India when the Delta variant emerged, India was the main producer of the AstraZeneca vaccine at that time (amid global shortages and very high covid burdens), it will have saved so many lives in India alone across 2021 and 2022.

“There are known adverse events, such as the blood clots, but these are rare, and the safety profile is overall very good. For comparison, the accepted rate of blood clots is much higher in medicines prescribed in areas of women’s health, such as the combined pill.

“The key reason for the withdrawal is likely to be that other covid vaccines, such as Pfizer and Moderna, are essentially better products. AstraZeneca is very good, but the mRNA products (and probably Novavax too) are better.

“They have higher effectiveness and the mRNA platforms are more easily adapted towards the latest covid variants. Thus, they form a key part of most countries’ longer-term strategies.

“With that, orders for the AstraZeneca vaccine are probably much lower now than they were in previous years, so it’s not worth a longer-term investment on the part of the manufacturers.

“Perhaps its time has passed. But, the Oxford AstraZeneca vaccine has played a key role in the pandemic response for most countries around the world.”

Declared interests

Prof Openshaw:

Relevant financial relationships:

– employed by Imperial College London;

– SAB member for Janssen, Moderna, Cephid, Seqirus, Pfizer, GSK and Sanofi, AstraZeneca (RSV, COVID and/or influenza vaccines.)

Relevant non-financial relationships:

– Collaborative Grant co-funded by MRC (UK) and GSK: EMINENT and INFLAMMAGE.

– Grants from Medical Research Council and NIHR.

Dr Head: No conflicts to declare