The AstraZeneca vaccine has saved millions of lives – it should not be demonized

Last week, the pharmaceutical company AstraZeneca announced that its coronavirus vaccine was being discontinued and would therefore no longer be produced or supplied. This was accompanied by scary news headlines about its ability to cause “rare blood clots” – but these are unnecessarily scary headlines. Essentially the situation is this: there is no new “smoking gun”; the AZ vaccine was one of the first and cheapest vaccines; it has saved millions of lives worldwide; and better vaccines are now available, adapted to new variants.

The AZ vaccine was one of the first to be approved in late 2020, cheaper than Pfizer and, most importantly, easier to distribute and administer with fewer resources because it did not require super-low temperatures for storage. AstraZeneca also offered a guarantee of 300 million doses of the vaccine on a non-profit basis to make it more accessible to low- and middle-income countries.

In most countries, it was first rolled out to older adults, as they were the population most at risk. When it was introduced to younger adults, a very rare, serious side effect was noted: It could cause fatal blood clots in the first few weeks after the first dose.

Vaccine-induced immune thrombocytopenia and thrombosis (VITT) was a new, rare condition that affected approximately one in 50,000 AZ vaccine recipients under age 50, and one in 100,000 among those age 50 and older. Crucially, this was quickly noticed and studied. Established vaccine monitoring protocols did their job. It should also be emphasized that no long-term effects of the vaccine have been reported (monitoring of side effects continues long after the initial vaccine rollout) and that the rare cases of VITT all occurred shortly after vaccination.

Many countries subsequently (mid-2021) restricted the AZ vaccine to older populations, as long as their populations had access to other vaccines, such as the Pfizer mRNA vaccine. The AZ vaccine remained much safer than contracting Covid, if only when you consider the risk of blood clots. For example, a Covid infection was 190 times more likely to cause a blood clot in the vein and about nine times more likely to have a low platelet count.

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Because the AZ vaccine was affordable and relatively easy to roll out on a large scale, it was widely used in that first crucial vaccine year of 2021, especially in lower-income countries. Its effectiveness has been extensively studied and it reduced serious infections by 90 percent. Imperial College estimated that all Covid vaccines had saved around 20 million lives by the end of 2021. A further study by vaccine type estimated that the AZ vaccine in particular had saved more than six million lives by the end of 2021.

In terms of updating the vaccine for new variants, the way the AZ vaccine is made means this takes longer and is harder to do than mRNA vaccines like Pfizer and Moderna. Specifically, the AZ vaccine is an example of a viral vector-based vaccine. We have different ways in which we make vaccines, and this is one that has already been used for diseases like Ebola. These vaccines use a modified virus, which we call the vector, to deliver the genetic code for, in this case, the coronavirus spike protein, into our cells. The viral vector is usually a harmless virus that we have probably not been exposed to before, such as a monkey adenovirus (a mild cold virus).

The vector is weakened so that it cannot multiply in our cells and cause disease. The viral vector will infect our cells and instruct them to make large amounts of antigens, which then trigger an immune response. In effect, the vaccine causes what usually happens naturally with a viral infection. This has a huge advantage because these types of vaccines are incredibly good at stimulating our immune cells (particularly our T and B cells). The T cells can target virally infected cells for destruction and the B cells can make antibodies, and both cell types will also generate memory cells.

Although this is an established technology for making vaccines, its production is complex and this is one of the reasons that this technology is not well suited to being adapted to an ever-evolving virus. Another reason is that previous exposure to the viral vector may reduce its effectiveness if used multiple times; there is a chance that your immune response will recognize and destroy the vector before it has a chance to deliver its vaccine package, making the AZ vaccine less suitable for regular boosters.

In the context of Covid-19, where we have had a constantly changing range of variants and sub-variants, there was always a finite lifespan for this vaccine. As of 2023, organizations such as the World Health Organization (WHO) no longer recommend targeting the original coronavirus spike protein for vaccine production. The current recommendations concern a further shift to the JN.1 variants.

All this means that three years later, better vaccines exist that are cheaper, (even) safer and faster to update than the AZ vaccine. It is simply no longer needed and has been retired. There is nothing shameful about this situation and most importantly, it does not detract from the vital role the country played in saving millions of lives around the world in 2021.

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