[News]How do we know Covid vaccines are safe?

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The Oxford-AstraZeneca vaccine has been linked to very rare cases of blood clots.

The chance of this happening to an individual is still extremely low, but as a precaution, younger age groups in the UK are being offered alternative vaccines.

What's happened?
Some recently immunised people have suffered unusual clots, including a type in the brain called cerebral sinus vein thrombosis (CSVT).

This is not proof that the vaccine is to blame. Covid infection itself can also make clots more likely and they can occur naturally too.

Experts stress the benefits of vaccination outweigh the risks for the vast majority of people, but is more finely balanced for younger adults.

As a precaution, regulators are continuing to monitor the situation and advise symptoms, such as unusual bruising or persistent headache after vaccination, should prompt a medical check.

 

How do we know a vaccine is safe?
Safety trials begin in the lab, with tests and research on cells and animals, before moving on to human studies.

The principle is to start small and only move to the next stage of testing if there are no outstanding safety concerns.

When will I get a coronavirus vaccine?
What role do trials have?
If the safety data from the labs is good, scientists can check the vaccine or treatment is effective.

That means tests on large numbers of volunteers - about 40,000 in the case of Pfizer-BioNTech, the first to be approved in the UK.

Half are given the vaccine and the other half a placebo jab. The researchers and participants are not told which group is which, until after the results, to avoid bias.

https://www.bbc.com/news/health-55056016