Also, what's the overlap here between people who believe a) the unborn have a "right to life" (or forced birth as some others call it, where the parent has no choice but to take the pregnancy to term and give birth), and b) those who think the parents have every right to decide not to vaccinate their children? If you believe (a), shouldn't you believe (not b)? And if you believe (b), shouldn't you believe (not a)?

Indeed. A lot of antivaxxers mockingly say "my body, my choice" but they are highlighting their own hypocrisy, not anyone else's. One critical difference between the cases is that pregnancy is not contagious.

Agree. Also I don't think any adults were forcibly vaccinated again their will, they just lost out on certain societal privileges.

It seems like even that's not good enough. I have a few skeptics in my family and have had family members die from covid.

For a lot of people these aren't rational beliefs, they're beliefs based on appeals to emotion. They will only rationally re-evaluate those beliefs if you change the kind of media they consume.

For example:

Parents of Texas child who died of measles stand by decision to not vaccinate

https://abc13.com/post/texas-measles-death-parents-child-die...

Another thing that seemed to work is the unvaccinated getting sick themselves.

2/3 of the unvaccinated COVID patients who were admitted to hospital regretted their decision, declared they would promote the vaccine post-discharge, and declared they would get it post-discharge.

https://pmc.ncbi.nlm.nih.gov/articles/PMC8950102/