Why Covid Vaccines For Young Adults?

Covid deaths in 2020 age 18-29: 1465
https://www.cdc.gov/nchs/nvss/vsrr/covid_weekly/index.htm

Fully vaccinated 18-29 as of May 4: 9.857M (18.39% i.e. of 56.6M total population 18-29)
https://usafacts.org/visualizations/covid-vaccine-tracker-states/

Covid deaths all ages among fully vaccinated as of Apr 26: 132
Total fully vaccinated as of Apr 26: 95M
https://www.cdc.gov/vaccines/covid-19/health-departments/breakthrough-cases.html

U.S. Covid deaths 18-29 all time are 2000 out of 557K, i.e. 0.35%. So assume the same ratio applies to the 132 breakthrough Covid deaths: 0.35% * 132 = 0.46, so round up to 1 breakthrough death among 18-29yo.

In 9 pandemic months of 2020, deaths of 18-29 per million per month were
1465 deaths / 56.6 18-29yo population / 9 months
= 2.8 deaths per million per month of unvaccinated 18-29yo in 2020.

Assume the 9.587M 18-29yo have been vaccinated linearly for the first 4 months of 2021.
9.587M * 4 months / 2 = 19.7M vaccinated person-months. That's 1 death / 19.7M
= 0.05 deaths per million per month of vaccinated 18-29yo in 2021.

This fits with the clinical trial data. 95% efficacy means that a vaccinated group suffers 1/20 the symptomatic Covid cases of an unvaccinated group. The above estimate suggests vaccinated 18-29yo are 1/50 as likely to die of Covid as unvaccinated 18-29yo.

We estimated above that 1 of the 132 breakthrough Covid deaths were 18-29yo (i.e. double the 0.46 deaths you would expect in that cohort if breakthrough Covid deaths have an age distribution similar to regular Covid deaths). Note that 55 vaccinated 18-29yo would have had to die of Covid in Jan-Apr 2021 to match the 2020 per-million-per-month Covid death rate of unvaccinated 18-29yo.

There are no data suggesting vaccinated 18-29yo are suffering excess non-Covid deaths compared to unvaccinated 18-29yo. If there were real data saying this, then vaccinations for this cohort would be stopped immediately. (The Johnson & Johnson vaccine was paused after 6.8M vaccinations because 6 women aged 18 to 48 developed blood clots, and one of them died.)

Of course, even 2.8 deaths per million per month is trivial. The primary rationale for vaccinating young adults is now de-emphasizing herd immunity, and emphasizing the suppression of variants (like the one now ravaging India):
https://www.nature.com/articles/d41586-021-00728-2

FAQ on Covid vaccines for people younger than 18:
https://www.webmd.com/vaccines/covid-19-vaccine/news/20210329/faq-what-to-know-about-covid-19-vaccines-for-kids