From the date of the first vaccine, until 2 weeks after the second vaccine, the immune system goes through many changes enroute to gaining protection from serious illness. It is recommended to avoid immune system stress, exposure to any pathogens (e.g. visiting hospitals), physical exertion, etc. during the 2 week period immediately after the first vaccine. If one is infected with anything earlier than 2 weeks after the 2nd vaccine, it will be recorded as an unvaccinated infection.
Anyone (vaccinated, partially vaccinated or unvaccinated) who gets infected should immediately avail themselves of early treatment options, e.g. monoclonal antibodies (free and available in some states), upcoming antiviral tablets from Pfizer and Merck (in trials) or other therapeutics on the global market. Early treatment speeds recovery. Without early treatment, the graph of outcomes becomes complex.
Vaccine schedules can be designed to give the killed version first for some immunity followed by live vaccine to provide more robust immunity.
None of the COVID vaccines so far are live attenuated vaccines as far as I'm aware.
Why not just develop anther vaccine or two? Wasn't the point with the mRNA vaccines that they would easily be tweaked to target another spike?
https://en.wikipedia.org/wiki/Antibody-dependent_enhancement
https://www.nytimes.com/interactive/2021/08/10/us/covid-brea...
Minor live infections to build immunity is called variolation, it's a tactic that was used effectively historically against smallpox, but effectively got obsoleted by vaccination, which doesn't kill as many people.
Despite that, let's concede the vaccine does kill people: I'm not sure that's unethical though if more people end up dead because the population didn't quickly achieve immunity and stop the spread of the virus. There are a lot of ethical frameworks out there and in the US we are actually a majority rule so as a society we should generally be protecting the interests of the majority of people except in cases where it leads to sever oppression or breach of civil liberties. We are okay with the draft (forced risk of death) during times of war yet somehow when the enemy is unfamiliar in the form of a virus we aren't?
To confirm efficacy they gave the vaccine to half of a population likely to develop the disease naturally. Then they compared how many people for sick in each group. That's why testing took a year instead of 2 months, they have to wait for enrollees to get sick naturally.
If we ignore ethics, I guess we could get more nuanced efficacy information out of a small sacrificial population. But that is just not done. Not even during a pandemic.