Even with two vaccines now in the Emergency Authorization, we are many months away from reaching herd immunity levels, and worse, it is not entirely clear that we actually can reach that point at all. McKinsey research on Covid19 vaccines currently either authorized or close to authorization is dire (see https://www.mckinsey.com/industries/healthcare-systems-and-services/our-insights/when-will-the-covid-19-pandemic-end).
In basic terms, accounting for current immunity levels (effectively - infections-induced immunity) and assumed vaccines 95% effectiveness rate, but varying the assumed durability of the immunity gained from the vaccines, the U.S. will require 58-85% rate of vaccinations to reach herd immunity frontier (minimum level of immunity). One of the drivers for such high threshold for vaccinations is that, currently, no vaccine available is indicated for children.
While 58% threshold is hard, but feasible, 85% threshold is impossible, given the U.S. population heterogeneity in terms of attitude to vaccinations. American data on anti-vaccination advocates varies, but some recent indicators suggest that 23-25 percent of Americans are not willing to undertake Covid19 vaccinations (https://www.bostonglobe.com/2020/05/07/opinion/23-percent-say-they-wont-get-covid-19-vaccine/), and over time, the trend to avoid vaccinations has been rising prior to Covid19 pandemic (https://www.usnews.com/news/healthiest-communities/articles/2020-01-14/survey-fewer-people-now-support-vaccinating-their-kids-than-in-2001). A recent online survey of more than 2,000 U.S. adults, conducted by The Harris Poll found that 45 percent of Americans say something has caused them to doubt vaccine safety (https://www.infectioncontroltoday.com/view/45-percent-surveyed-american-adults-doubt-vaccine-safety).
Good luck getting far on the herd immunity curve with this crowd.