Four fully vaccinated Pennsylvanians caught measles as the state's outbreak topped 676 cases — a reminder that a 97% effective vaccine was never advertised as 100%.

Walking pneumonia isn't a seasonal illness like the flu. CDC data show it moves in multi-year waves driven by fading population immunity — and the latest one hasn't fully cleared.

For the first time in years, regulators rebuilt the flu vaccine from scratch, swapping the H1N1, H3N2, and B strains after a fast-mutating H3N2 variant cut protection in some patients to as little as 14%.

Four baby goats at a North Carolina petting zoo tested positive for rabies without ever looking sick. Here's why infected animals can seem completely healthy until it's too late.

Measles cases in the U.S. have already topped last year's total, and Pennsylvania just recorded the country's first deaths from the disease in 35 years. The reason it keeps returning comes down to one number: 95%.

A bottle of melatonin in an American drugstore can pack five to ten milligrams; the same supplement in France is capped under two. The regulatory gap has real consequences for how families use -- and mis-store -- a hormone most people assume is harmless.

The CDC has confirmed 48 West Nile cases by June 30, far above the usual 10, with Arizona hardest hit as officials urge simple precautions over the July 4 weekend.

The CDC has moved to its highest response level as the Congo-Uganda Ebola outbreak becomes the third largest on record. For US readers, the risk stays low.

For the first time, the American College of Obstetricians and Gynecologists released its own maternal immunization schedule on June 10, recommending four vaccines during pregnancy—including flu and COVID-19 shots that the CDC no longer endorses.