COVID has killed about as many Americans as the 1918-19 flu

In many ways, the 191flu — which was wrongly named Spanish flu because it first received widespread news coverage in Spain — was worse.

Spread by the mobility of World War I, it killed young, healthy adults in vast numbers. No vaccine existed to slow it, and there were no antibiotics to treat secondary bacterial infections. And, of course, the world was much smaller.

Yet jet travel and mass migrations threaten to increase the toll of the current pandemic. Much of the world is unvaccinated. And the coronavirus has been full of surprises.

Markel said he is continually astounded by the magnitude of the disruption the pandemic has brought to the planet.

“I was gobsmacked by the size of the quarantines” the Chinese government undertook initially, Markel said, “and I’ve since been gob-gob-gob-smacked to the nth degree.” The lagging pace of U.S. vaccinations is the latest source of his astonishment.

Just under 64% of the U.S. population has received as least one dose of the vaccine, with state rates ranging from a high of approximately 77% in Vermont and Massachusetts to lows around 46% to 49% in Idaho, Wyoming, West Virginia and Mississippi.

Globally, about 43% of the population has received at least one dose, according to Our World in Data, with some African countries just beginning to give their first shots.

“We know that all pandemics come to an end,” said Dr. Jeremy Brown, director of emergency care research at the National Institutes of Health, who wrote a book on influenza. “They can do terrible things while they’re raging.”

COVID-19 could have been far less lethal in the U.S. if more people had gotten vaccinated faster, “and we still have an opportunity to turn it around," Brown said. “We often lose sight of how lucky we are to take these things for granted.”

The current vaccines work extremely well in preventing severe disease and death from the variants of the virus that have emerged so far.

It will be crucial for scientists to make sure the ever-mutating virus hasn’t changed enough to evade vaccines or to cause severe illness in unvaccinated children, Antia said.

If the virus changes significantly, a new vaccine using the technology behind the Pfizer and Moderna shots could be produced in 110 days, a Pfizer executive said Wednesday. The company is studying whether annual shots with the current vaccine will be required to keep immunity high.

One plus: The coronavirus mutates at a slower pace than flu viruses, making it a more stable target for vaccination, said Ann Marie Kimball, a retired University of Washington professor of epidemiology.

So, will the current pandemic unseat the 191flu pandemic as the worst in human history?

“You’d like to say no. We have a lot more infection control, a lot more ability to support people who are sick. We have modern medicine,” Kimball said. “But we have a lot more people and a lot more mobility. ... The fear is eventually a new strain gets around a particular vaccine target.”

To those unvaccinated individuals who are counting on infection rather than vaccination for immune protection, Kimball said, “The trouble is, you have to survive infection to acquire the immunity.” It's easier, she said, to go to the drugstore and get a shot.