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A blood test being used to test for covid-19 antibodies

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To tackle the covid-19 pandemic, we need the most effective vaccines we can get. But even the best vaccines don’t work in everyone. How do you know if yours has worked?

All of the vaccines in use against the coronavirus can cause side effects, including a sore arm, fever, chills, headache and nausea, usually in the first two days after a jab.

These are more common after a second dose, and in people who have already been naturally infected with the coronavirus, according to data from …