I meant that in a future where you never have to fight viruses your immune system will be weakened.

From my layman's reading (start from https://en.m.wikipedia.org/wiki/Shingles#Epidemiology), I think the chickenpox vaccine is potentially somewhat the inverse of vendor lock-in: that giving the vaccine to children decreases the possibility of shingles complications later for them, while studies potentially show an increase in the prevalence of complications among unvaccinated older folks, thus making it relatively worse to not vaccinate for it, as you get older, and as others opt into it. Since there's also multiple shingles vaccines now, this sounds to me more like a typical network effect from vaccination?

To make up an unrelated tech example of that, my impression was this would be like picking a Blackberry phone, while all your friends have Windows phones. You weren't forced to pick a Blackberry by vendor lock-in, but you may miss out on being in some social circles. Changing that group dynamic would require everyone to switch, not just on a case-by-case basis. But in this example though, the Window's phones (aka vaccination) have strictly more features than the Blackberry (aka kills you less often), so if you can afford to (aka you have an average immune system), it would be more logical to get a new phone yourself and join the network, than to ask all of your friends to get new phones.