How strong is your Covid immunity? A blood test could offer some insight

A newly developed blood test that measures a specific immune response in the body could help doctors gauge how much protection a person has against Covid-19, according to a new study.

The test, which focuses on the part of the immune system that confers long-term protection by prompting the body to "remember" the virus, could help make sense of the complex tangle of Covid immunity that now exists from person to person.

The test can, for instance, measure immunity regardless of whether someone has developed a level of protection from one...