I have no records of vaccinations from my youth. I was born too late to have presumptive immunity to measles and mumps, but before it became standard for children to be vaccinated. Someone at my HMO said I should get a titer, but a doctor said that based on CDC guidance I should just get the MMR vaccination. There's no harm if you've had it, and also immunity decreases over time (which can be tested by a titer). I've got an appointment to get an MMR on Thursday. High-risk people should get two.