RUTHFULLY YOURS

Is a vaccine the only way to return to normal after ­COVID-19? New research into the virus suggests not — that the infection rate may drop to tiny levels before then.

Since the spring, scientists have known the virus’s infection fatality rate — how many people it kills compared to the number it infects — is under 1 percent, perhaps as low as 0.2 percent. That lower figure translates into one death for every 500 people infected.

We have also known that deaths are seriously skewed by age. The media says older people are at “more” risk from the novel coronavirus than younger people. That’s true, but it understates the reality. Most people do not realize that the risks to people over 80 are hundreds or thousands of times higher than those younger people face.

The fatality rate for children, meanwhile, is very small. In July, Dr. Robert Redfield, director of the Centers for Disease Control and Prevention, said it’s about one in a million infected.

Of course, most of the media simply ignored Redfield’s comment — maybe because it would have made parents less afraid to send their kids to school.

But the fatality rate is only half the puzzle when scientists try to figure out what the final death toll from the coronavirus might be. And even with a small rate, the numbers are staggering. If the entire nation was infected, it would mean potentially 500,000 or more Americans dead.

But if the virus runs out of steam more quickly and the epidemic fades before everyone is infected, the number of deaths will be lower.

Epidemiologists call the level where the epidemic ends the “herd immunity” threshold. Herd immunity does not mean that the virus has completely disappeared, only that it can no longer infect a critical mass of people and become an epidemic again.

Figuring out when a virus has reached herd immunity is very tricky, even trickier than estimating the death rate. It depends heavily on the virus’s reproduction number, or R — how many people one infected person infects in turn.

The higher the R, the more quickly a virus will spread, and the more people must be infected before the epidemic breaks. Coronavirus seemed at first to be highly contagious, and most scientists initially believed that 60 percent to 80 percent of people might need to be infected before herd immunity was reached.

But the R for the coronavirus seems to vary wildly at different times and places. Also, some people may have some pre-existing immunity because of their exposure to other coronaviruses.

A growing number of scientists believe the threshold for herd immunity may be much lower. Some predict it might be 40 percent. Others say it could be as low as 20 percent — meaning that the epidemic will burn out after only 1 in 5 people is infected with and recovers from the virus.

And real-world evidence — from Sweden, from Sunbelt states like Arizona, and now from the Brazilian city of Manaus — provides very encouraging evidence that the immunity threshold may be well below 50 percent. Sweden, Arizona and Manaus don’t have much in common, but in all of them, the epidemic burned out relatively quickly, without hard lockdowns, and after a relatively low number of people were infected based on antibody tests.

If we can actually reach herd immunity after 40 percent or less of the population is infected, far fewer people will die than the early forecasts, even without lockdowns. And if the best-case estimates of 20 percent or less are correct, we may be closer to the end than the beginning of the coronavirus epidemic. It’s still too early to be certain — but maybe for the first time since March, we have real reason to hope.

Alex Berenson, a former New York Times reporter, is the author of “Unreported Truths About COVID-19 and Lockdowns: Parts 1 and 2,” both available on Amazon.