Science

On the heels of last month’s news of stunning results from Pfizer’s and Moderna’s experimental Covid-19 vaccines, Senator Rand Paul tweeted a provocative comparison.

The new vaccines were 90 percent and 94.5 percent effective, Mr. Paul, Republican of Kentucky, said. But “naturally acquired” Covid-19 was even better, at 99.9982 percent effective, he claimed.

Mr. Paul is one of many people who, weary of lockdowns and economic losses, have extolled the benefits of contracting the coronavirus. The senator was diagnosed with the disease this year and has argued that surviving a bout of Covid-19 confers greater protection than getting vaccinated.

FULLERTON, Calif. — The post-Thanksgiving rush for coronavirus testing is on: Pharmacies in the Southern California suburbs are advising customers lucky enough to score appointments that it could be four days before they receive results. In Chelsea, Mass., a line of people who hoped for testing, pelted by rain and wind, strung along an entire block early this week. In Atlanta, people have idled in cars, sometimes for hours, to get swabbed at drive-throughs.

Testing has long been one of the keys to controlling the spread of a virus that with the onset of winter is entering its most dangerous phase. Yet even as cases per capita have rocketed, securing a test has become enough of an ordeal that many people have been dissuaded from even trying.

SEOUL, South Korea — The deaths were mounting, and so were the public’s fears.

South Korea had vastly expanded its flu vaccine program to cover millions more people, to prevent a one-two punch to its health system as the coronavirus spread globally. But as the injections got underway, reports of deaths started popping up.

South Korean scientists quickly determined that the deaths were unrelated to the flu shots. But they worried that if they didn’t stop the panic, the public might shun the vaccines altogether.

So health officials doubled down — and, in the process, gave the world a game plan for when coronavirus vaccines become widely available.