Covid-19 patients who are 80 or older are hundreds of times more likely to die than those under 40.

That’s partly because they are more likely to have underlying conditions — like diabetes and lung disease — that seem to make the body more vulnerable to Covid-19.

But some scientists suggest another likely, if underappreciated, driver of this increased risk: the aging immune system.

The changes that ripple through our network of immune cells as the decades pass are complex, resulting in an overreaction here, a delayed response there and over all, a strangely altered landscape of immunity.

Scientists who study the aging immune system say that understanding it may lead not only to a clearer sense of how age is connected to disease vulnerability, but to better strategies for vaccines and treatments for Covid-19.

The first famines of the coronavirus era could soon hit four chronically food-deprived conflict areas — Yemen, South Sudan, northeast Nigeria and the Democratic Republic of Congo — the top humanitarian official of the United Nations has warned.

As hope builds over possible frequent at-home testing, experts call the idea a long shot.

Over the past few weeks, a Harvard scientist has made headlines for a bold idea to curb the spread of the coronavirus: rolling out antigen tests, a decades-old underdog in testing technology, to tens of millions of Americans for near-daily, at-home use.

WASHINGTON — Chinese intelligence hackers were intent on stealing coronavirus vaccine data, so they looked for what they believed would be an easy target. Instead of simply going after pharmaceutical companies, they conducted digital reconnaissance on the University of North Carolina and other schools doing cutting-edge research.