Over the weekend I realized that my son Henry, born in June 2019, has lived more than half of his life in the pandemic era. He’s too young to be cognizant of it, of course, but my wife and I are acutely conscious of the experiences his older brother had already enjoyed by the time he was Henry’s age, things that are impractical or impossible in the moment.

He’s not alone in that, of course. Most Americans are experiencing some ongoing deprivations because of the pandemic. (Most of those for whom the pandemic is not imposing unusual restrictions are, ironically, probably contributing to the pandemic’s extent and duration.) Just about everyone in the United States is eagerly scanning the horizon for signs of normalcy — as we have been for months, occasionally spotting oases that too often turn out to be mirages.

So when will we return to some semblance of normal? It’s hard to say with certainty. The best tool we have to reach that point, though, is the broad deployment of the vaccines approved for emergency use by the government. But even the existence of those vaccines can’t completely answer the question.

For example, the rate at which the vaccines are deployed makes a massive difference. A pace of 2 million shots per day as opposed to 1 million seems like a subtle distinction but, obviously, means achieving immunity for recipients twice as fast.

What level of immunity is necessary is a question of its own. Do we need 70 percent of the country to have been immunized? Or, as infectious-disease expert Anthony S. Fauci has recently said, is the figure closer to 80 or 85 percent?

When doing this calculation, do you include the 26 million Americans who have already had coronavirus infections? What about young people? The vaccine trials included only those age 16 and over. Those younger have constituted about a 10th of the total infections. And what vaccine are we talking about? The Pfizer and Moderna iterations require two shots; the vaccine from Johnson & Johnson requires only one.

All of these factors affect how we can figure out when the country might hit the herd-immunity mark. If we assume that young people will be included among those needed to be vaccinated — a complicated question on its own — the calculator below will allow you to figure out when immunity might be achieved at various immunization rates.

Shots administered per day nationally:
1.5 million

Herd immunity achieved at:
80 percent

Doses required:

Vaccinate those already infected?

(All figures used in the interactive are current as of Feb. 1.)

Bear in mind that sliding the little bar to determine how quickly shots are administered is far easier than actually scaling up the infrastructure to do so. President Biden’s original target for daily vaccinations was 1 million; he recently increased it to 1.5 million. At that rate, we’re still months from resolution. But because administering the vaccine is more complicated and requires more tracking than vaccinations such as that for the seasonal flu, it’s necessarily trickier to scale up.

At this point, the more urgent concern is the efficacy of the vaccine against any variants of the virus that might emerge. Manufacturers have already noted that the vaccine works less well against a virus variant first identified in South Africa, though the vaccines are still broadly effective, particularly at protecting the recipient from severe illness or death after infection.

Well, that and the fact that a fifth of Americans said in a recent Kaiser Family Foundation poll that they won’t get the vaccine or would do so only if it was required. Happily, more Americans are now saying they’re eager to get a vaccine.

The faster we get people immunized, the better we protect against the emergence of new mutations that prove less able to be controlled by the vaccines. The faster we get shots in arms, as the phrasing has it, the faster we get back to normal.

Which would be nice for all of us, including my 1-year-old.