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I'm so glad that I've received two Astra inoculations. The role of killer T-cells is downplayed in favour of antibodies but long term are more effective.
Last week, AstraZeneca’s chief executive officer said the company’s COVID vaccine may provide longer-lasting protection than mRNA vaccines like Pfizer’s, especially in older people.
CEO Pascal Soriot said this might explain the United Kingdom’s more stable hospitalisation rate compared to the escalating COVID situation in continental Europe.
The UK used the AstraZeneca vaccine a lot more widely than other European countries, many of which restricted its use to older age groups or abandoned using it altogether after reports of very rare blood clots.
The theory behind this is the AstraZeneca vaccine may provide more durable “T cell protection”. T cells are a crucial part of our immune system, and differ from antibodies.
There’s not enough evidence yet to support the CEO’s claim. But we do know a lot more about adenovirus vector vaccines, such as AstraZeneca’s, as they’ve been around for decades, while mRNA vaccines are relatively newer.
Theoretically, it is possible adenovirus vector vaccines do give more durable protection against COVID via T cells.
Let me explain.
What is AstraZeneca’s vaccine again?
AstraZeneca’s COVID vaccine is an adenovirus vector vaccine.
This means it uses an adenovirus – a common type of virus that affects humans and many other animals. The adenovirus is genetically modified so it doesn’t replicate.
It’s used as a way to deliver the vaccine’s information into our cells.
In this case, the information packaged in the adenovirus tells our body how to make the coronavirus spike protein. This teaches our immune system how to deal with the coronavirus if we’re exposed.
Adenovirus vectors have been used in medicine for a few decades in other vaccines and also cancer therapy. They’re very good at stimulating both antibody production and T cell responses.
What are T cells?
Antibodies bind tightly to a specific target, locking onto invading viruses and preventing them from entering our cells.
But the immune system is more than just antibodies.
T cells are also really important for our immune response, and have different roles. One type, known as “killer T cells”, attack and destroy virus-infected cells.
Another type, known as “helper T cells”, interpret the nature of the infection and help the immune system respond appropriately. This includes activating killer T cells to destroy virus-infected cells, and also helping B cells make antibodies
Antibodies wane over time, which can lead to more breakthrough infections in fully vaccinated people.
When viruses are not stopped by antibodies, we rely on killer T cells to eradicate the virus. And T cells almost certainly help prevent severe outcomes if you get COVID.
It’s a lot harder for a virus to escape a T cell-based immune response. So a vaccine that generates strong T cell immunity should help retain effectiveness over time against variants including Delta and Omicron.
https://theconversation.com/does-ast...a-shots-172609
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