Just learned about this today. I could have put it on the science board, but I think it's relevant here. SSPE is a -mostly- fatal mutation of measles that can happen in people that don't have the vaccine. It's informally classified as a "zebra". Extremely rare in the age of vaccines. But with the present attacks on vaccinations, and the subsequent rise in the occurrence of measles, we can expect to see this become more prevalent. The measles virus lays dormant, usually in the brain, and 10-15 years later it becomes SSPE. Extremely difficult to treat, and "universally" fatal when it reaches stage two.

Google it. Some scary excrement. Just from measles. From the description of symptoms, it's a nasty way to die.

Get your kids the MMR, and make sure you're fully boostered.