The United States is in an enviable position relative to a year ago. Then, the extant spread of the coronavirus was still unknown, detected only sporadically thanks to limited testing. Within weeks, tens of thousands of Americans would die of covid-19, the disease caused by the virus. Within months, hundreds of thousands more would succumb.

Now, the picture is different. More people have been vaccinated against the virus than have contracted it, a remarkable achievement. Those vaccinations are enormously effective, with no indications that anyone has died of the disease after being vaccinated. The country has secured enough supply to vaccinate everyone in the country more than once.

Being in such an enviable position, though, means that other countries with less capacity to invest in vaccine regimens might envy where we are. There’s been an increased call for the United States to share its bounty internationally, including among those who point out that providing an escape route from a deadly disease offers a significant geopolitical upside.

Obviously U.S. leaders want to ensure Americans have access to the vaccine and that the country reaches herd immunity as soon as possible. A review of purchasing agreements compiled by the Duke University Global Health Innovation Center makes clear that the United States is in no danger of being undersupplied. Quite the opposite.

Consider the Pfizer-BioNTech vaccine alone. The United States has secured — though not yet received — 300 million doses, enough to vaccinate 150 million people. There are about 266 million Americans ages 16 or over who need to be vaccinated, meaning that with the entire Pfizer complement alone we would get more than half of the way there. Add in the 300 million doses of the Moderna vaccine (which again requires two doses) secured by the government and every American over 16 is covered and then some.

Particularly once you take out the 30 percent of Americans who say they won’t get the vaccine, according to a recent NPR-PBS NewsHour-Marist poll, you cover every eligible, willing American with all of the Pfizer doses and less than a quarter of the Moderna total.

If we eventually expand vaccinations to those younger than 16, which seems likely, we have enough doses to meet the task from a Johnson & Johnson stockpile. That vaccine requires only one inoculation and the United States has secured enough to cover 100 million of the 330 million-plus U.S. population. If we used the vaccines in the order they were approved for use and had all of them in hand, we could run through Pfizer, Moderna and less than a third of the Johnson & Johnson doses and cover every man, woman and child in the country.

But as of Monday, the United States also seemed poised to approve the Oxford University and AstraZeneca vaccine. The Biden administration has already agreed to ship 7 million doses of the vaccine to Mexico and Canada — eating only slightly into the total. On top of that there are agreements to acquire vaccines from Sanofi and Novavax.

To put it bluntly: The total number of vaccines secured by the United States is almost twice the number needed to vaccinate everyone, even after considering that most of the vaccines require two doses for full effectiveness.

Again, it’s understandable why the government would want to make sure that Americans were able to get a sufficient number of effective vaccines before pledging to share them with other countries. But that’s the other cloud hanging out there. The longer it takes to reach herd immunity globally, the more possible it is that a variant of the virus will emerge that renders the vaccines ineffective.

Hence the calls to be as generous as possible as soon as possible.