With some health care workers still refusing to be immunized, medical centers around the country are requiring shots as cases climb once again.

About three million adults in the U.S. have been diagnosed with A-fib, a heart-rhythm abnormality that’s on the rise. Here’s how to recognize the signs and treat it.

The growing consensus that at least some Americans will need a booster is partly tied to research suggesting that Pfizer’s vaccine is less effective after about six months.

With only about half of Americans vaccinated, Dr. Anthony Fauci and other current and former health officials vigorously pressed the case on Sunday that inoculations were the best way to stem a tide of new Covid cases.

There are almost as many reasons for vaccine hesitancy and refusal as there are unvaccinated Americans. But this problem, not the variant, lies at the root of rising infection rates.

Frequent screening of healthy, vaccinated people will pick up even the mildest infections. How much testing is too much?

If funded, a government program costing several billion dollars could develop “prototype” vaccines to protect against 20 families of viruses.

The U.S. vaccine rollout has plateaued and the course of the coronavirus pandemic in this country may depend on how many people are ultimately swayed to get vaccinated.

The measure prohibits health professionals from revealing your medical records, but it is perfectly legal to ask whether someone has been vaccinated.

Researchers and regulators say Joseph Mercola, an osteopathic physician, creates and profits from misleading claims about Covid-19 vaccines.

Staffing shortages have long plagued the home care industry. But the pandemic has intensified the problem.

The new numbers still show overwhelmingly strong protection against severe disease but diminished effectiveness against infection.

The vaccines are effective at preventing serious illness and death, but they are not a golden shield against the coronavirus.

For the first time, the C.D.C. identified several cases of Candida auris that were resistant to all drugs, in two health facilities in Texas and a long-term care center in Washington, D.C.

He explored how viruses multiply. An accomplished administrator, he also turned the Howard Hughes Medical Institute into a global biomedical powerhouse.

To get out of conservatorship, the pop star will likely have to undergo a psychiatric evaluation, an uneasy melding of legal standards and mental health criteria.

Plus, orphaned grizzlies, baby deer in the shower, hoot-owl restrictions and more in the Friday edition of the Science Times newsletter.

DeepMind has given 3-D structure to 350,000 proteins, including every one made by humans, promising a boon for medicine and drug design.

The renewed sense of urgency was aimed at millions of people who have not yet been vaccinated and therefore are most likely to be infected.

With daily reports of breakthrough infections and the rise of the Delta variant, vaccinated people may need to take a few more precautions. Here’s what you need to know.