There are genuinely people who cannot get them due to compromised immune systems, egg allergies on the ones that can only be grown in eggs, and some people have sensitivities to them (had a coworker who had gotten sick after a vaccination in the past but not all vaccinations, then had the flu shot and got very very sick, developed Guillain-Barre syndrome, got walking pneumonia, severe kidney swelling, etc. I had a flu shot from the same batch/provider/etc. 15 minutes earlier and zero wrong with me or anyone else at work, but she was in and out of the hospital for months.) Those who can and do get the vaccines help provide a herd immunity for those who can't get them. There is currently an issue where there are people immigrating w/o standard vaccination scheduled vaccines (MMR, Dtap, and the like) and there are now resurgences in areas of high concentrations of those unvaccinated populations. Herd immunity doesn't work unless ~90% of the 'herd'/population has the vaccine/immunity.
https://www.google.ca/amp/amp.timeinc.net/time/5175704/andrew-wakefield-vaccine-autism
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https://www.google.ca/amp/s/www.vox.com/platform/amp/2018/2/27/17057990/andrew-wakefield-vaccines-autism-study
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There's a dozen other websites that talk about it, if you dislike these sources