Information about incubation period of measles:
" The incubation period from exposure to onset of measles symptoms ranges from 7 to 14 days (average, 10-12 days). Patients are contagious from 1-2 days before the onset of symptoms. Healthy children are also contagious during the period from 3-5 days before the appearance of the rash to 4 days after the onset of rash. On the other hand, immunocompromised individuals can be contagious during the duration of the illness."
https://www.medscape.com/answers/966220-87114/what-is-the-incubation-period-for-measles
Vaccinate AFTER exposure? Hmmmm?