Regarding the July 29 front-page article “CDC mask guidance confuses, frustrates”:

The coronavirus has changed. When we hoped we had conquered the disease with vaccines, it mutated and has caused infections in much of the United States to skyrocket again. It is irrational for anyone to be confused or hostile because medical experts are reacting to the variations and changing their advice to wear masks.

 As Ralph Waldo Emerson said, “A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines.”  I add, “And adored by people who do not care about their own safety and the safety of others.”

Hollis Raphael Weisman,

Whether one shares Megan McArdle’s generally libertarian views, one has to admire her mindfulness and powers of prognostication. Case in point: Ms. McArdle wrote in her Feb. 3 Wednesday Opinion essay, “What if it never really ‘ends’?”: “What if the virus gets more contagious and even more lethal? . . . What if the virus keeps reinventing itself and evading our immune defenses, so much so that it’s not possible to reach herd immunity without continually updated vaccinations? What if the pandemic never really ‘ends’?”

So here we stand six months since Ms. McArdle — coincidentally or not — effectively framed the covid challenge facing us today. The six-month echo from early February is a timely reminder that the coronavirus — its lethality, transmissibility and variability — is as potent as ever and as demonstrably hard to contain.

Steve Horwitz, Odenton

In her July 28 Wednesday Opinion essay, “Vaccines are the best weapons we have,” Alabama Gov. Kay Ivey said that all those involved in Operation Warp Speed, which produced vaccines in record time, deserve our thanks, including former president Donald Trump.

Successful vaccines were also produced in Britain, Russia and China, so the speed with which they were made available is a tribute to the scientific progress in this field. Mr. Trump had shown little interest in scientific issues until it became clear that an early vaccine might bail him out from the incompetence and indifference he had shown in his approach to the coronavirus.

Our thanks should go to the vaccine developers and those involved in the delivery processes.

J.B. Cowie, Silver Spring