Diseases, Conditions, Syndromes

S.Africa virus strain poses 're-infection risk': study

The coronavirus variant detected in South Africa poses a "significant re-infection risk" and raises concerns over vaccine effectiveness, according to preliminary research Wednesday, as separate studies suggested the British ...

Vaccination

Do I need a vaccine if I've already had COVID-19?

The Centers for Disease Control announced that in most cases, vaccinated adults in the U.S. could start going without masks, even indoors—a long-awaited benchmark to signal a return to a more normal life. But many people ...

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