@H T C is mostly right. The U.S. was one of the earliest to begin COVID vaccinations, and our aggregate vaccination numbers don't look too bad compared to UK or even Israel (except they have boosted millions). However, if you drill into it, you'll see massive disparities in where vaccines have been given. Namely, immunization is highest in the Northeast and a handful of Western states. This is why U.S. hospitals are getting hit so hard in this 4th wave, because communities in many states have effectively low levels of immunity. The UK for example has held up better despite sustaining very high infection counts for
months now. It may sound well and good that 83% of U.S. seniors (age 65+) are fully vaccinated, but this figure masks the uneven distribution across the country.
Your point is correct in that employees at nursing homes have a low vaccination rate, and frankly COVID vaccination should have been mandated sooner rather than later. Unfortunately, the U.S. is also experiencing massive staffing shortages in various industries so there are knock-on effects to vaccine requirements.
To paraphrase what H T C is saying, it wouldn't matter that much if you vaccinated every single teenager in the U.S. They probably spread a lot of SARS-CoV-2, but they aren't developing severe COVID and inundating hospitals. I don't have the data in front of me, but we all know that most of the 1800 dying daily still trend older and unvaccinated. To be clear, I'm not saying we shouldn't vaccinate younger Americans. Just that age 0-17 are still a small portion of COVID hospitalizations, and an even smaller portion of deaths.