It's all 50/50 anyways. Well, more like 65/35 (according to the last statistics of hospitalised people, where I live in), but still, even when vaccinated (and boosted), you can still contract the disease and be contagious.

It's not like the smallpox vaccine that actually managed to completely eradicate the disease that killed 90% of the Aztecs - old and young, healthy and otherwise. Or polio, for that matter. Or measles... hmm...

Anyway, my personal bitterness aside, I would say as long as your partner's partner isn't going around licking seats and handrails of metros, avoids exposure to heavily packed masses of people, and knows to stay home when feeling under the weather, you're as safe as safe gets in our new reality.