The L.A. County Department of Public Health reports most of the people infected so far have not been vaccinated. But in one case, an infected person had only received one of the two required measles, mumps and rubella shots.
Here are some questions you've asked via social media, along with answers from experts:
What happens when someone with measles exposes others to the disease at a movie theater?
"A person in a movie theater who has measles is the classic case that you don't want to have happen," Chief Medical Officer at Verdugo Hills Hospital of USC Dr. Armand Dorian
But it's happened more than once. Doctors tell us the virus can survive in a room two hours after an infected person has left. So if you're in a theater for three hours, that's five hours of potential exposure.
"When people get in crowded areas, the potential for measles to spread is high," Dorian says.
That's why CDC officials are now urging people unsure of their immunity who live near areas of known exposure to get another dose of the measles vaccine. The concern is for those born between 1957 and 1989 who don't know their level of protection.
"There is a concern when there are outbreaks that adults that might assume they're protected are not," Dorian said.
Are people who are vaccinated still at risk from those who are unvaccinated?
"It is possible. In the case of measles, about three percent of fully vaccinated people may still get the disease," said Pediatrician Francisco Rivera, M.D. with the Huntington Plaza Pediatric Group said
When I was a kid, my doctor wouldn't vaccinate me because I was allergic to something in the vaccine. So how can I keep from getting the measles?
Rivera says egg allergies are no longer an issue.
"A lot of those egg proteins have been removed and are not considered an significant risk," Rivera said.
Doctors say the best way to prevent contagion is make sure as many people as possible are vaccinated.
How long does an MMR vaccine last? I had a booster in 1975. Will I need to get another dose?
Dr. Dorian said, "You do not need to get re-vaccinated. It's for your entire life. If you got both doses, you will have the immunity for your entire life."
I got the measles shot when I was younger. But now I have different autoimmune disorders. Do I need a shot?
"If your immune system is weak, we would recommend one of two options. One, get a booster shot, or two, check your titers and see how good your body is prepared to fight measles. "
A small subset of people can't get vaccinated. Dr. Dorian said these are the people who rely on us to protect them.
"If there's enough people who have been vaccinated, its starts protecting those even who are not vaccinated," he said. "Look at what's happening now. Put all of these pieces together. The measles vaccine does not cause illness, it prevents illness."
How contagious is it?
Dr. Rivera said it's "very contagious."
"If somebody is not immune, they have a 90% chance of getting the measles," Rivera said.
If you aren't immune, you can still get infected for up to two hours after that person left the room.
Why are children who are vaccinated against measles at risk from those who are not vaccinated?
"It is possible in the case of measles that about three percent of fully-vaccinated people may still get the disease," Rivera answered.
"I'm going to LAX in two weeks with a two month old...will she be safe?"
"If the mom had measles or immunity thru the vaccine, there's a very good chance that the baby is protected. There are a lot of circulating anti-bodies protecting the mom that will still be protecting the child," Rivera said.
And what if you're pregnant and you're not sure you've been vaccinated?
"Women who are currently pregnant or may become pregnant should not get the MMR for theoretical reasons," Rivera said, "It could be harmful to the new baby but it's not well established. "
Rivera warned, "if you think you have been exposed to the measles, don't go rushing into the doctor's office without calling first."
"If we need to see you in the office we will make arrangements to to have you come in through a separate entrance and isolate you as soon as possible," he said.
A blood test can determine your immunity. With new outbreaks happening every day, it's always better to safe than sorry.
If you were born in the mid-1960s and received one vaccination in the mid-1970s, does she need to be vaccinated again?
The CDC website says there's a small percentage of people who may have received the "killed" version of the vaccine from 1963 to 1968. If you're unsure if you fall into that group, talk to you doctor about testing your blood.
And when in doubt, Dr. Diane Tanaka with Children's Hospital Los Angeles said, "It's easier and quicker to just get a booster. There might be a cost with having a measles titer draw because it's a lab test."
"I was born in the early 1950s and had measles as a child. I'm around small children. Should I get vaccinated?"
The answer is - if you know you've had the measles, you are immune. However, if there happens to be an outbreak in a place that you've been to recently, you can still get quarantined.
Dr. Barbara Ferrer, Director of the L.A. County Dept. of Public Health said, "You would need to actually show us proof of immunity. If you came in contact with a person with measles, you would need to get a blood test."
How long does the MMR vaccine last in adults?
The CDC says if you've had two shots, then you are immune and there is no need for a booster.
Health officials say people infected with measles can be infectious for up to four days before you see any sign of a fever or rash.
"Unintentionally, you could be in a lot of public settings not knowing that you're infectious and in fact exposing a lot of people to this virus," Ferrer said.
Keep in mind, if you are not vaccinated, doctors say you have a 90 percent chance of getting the measles if you are exposed.
MORE: Measles outbreak in Southern California - Everything you need to know
MORE: How can you tell if you're protected against the measles?