There's a lot of talk about vaccinations for children to protect them from highly contagious viruses and diseases, but what about adults?
According to the Center for Disease Control and Prevention, as of Monday, the number of measles cases this year is now at 626. That's the second highest in more than a decade.
Nearly two decades ago, the measles was declared eliminated in the U.S., but there has been an upsurge of cases, including adults who thought they were already protected.
It's likely some adults might not remember shots as children, or have lost their documentation.
Depending on where they were born, those adults might not have been given the vaccine at all.
If you were born before the 60's, you may have never been vaccinated because it was assumed you'd be exposed to the virus and would build immunity.
The group of adults that may be at risk are 'Generation X,' which are those born in the late 60's, 70's and 80's.
These adults may have been vaccinated, but never built immunity, mostly because of the way the vaccines were administered.
In 1989, the CDC began recommending two doses of the MMR vaccine, which covers the measles, mumps and rubella, making the vaccine consistently more effective.
If you're unsure of your immunity, health officials recommend contacting your doctor.
The CDC said it's safe to get another dose.
Two doses are about 97% effective at preventing measles; one dose is about 93%.