A rare but serious clotting disorder linked to certain COVID-19 vaccines and natural adenovirus infections has puzzled scientists for years.

SAN FRANCISCO (KGO) -- Preliminary data out of South Africa is giving the world insight into how strong omicron really is. The South African Medical Research Council just reported this variant may ...

Have you ever wondered why you have to get a flu shot every year, but some vaccines are one-and-done? It all has to do with how and how fast viruses evolve - and that depends on mutation rates.

(CNN) — The United States may be heading into its second severe flu season in a row, driven by a mutated strain called subclade K that’s behind early surges in the United Kingdom, Canada and Japan.