The growing measles outbreak that began at Disneyland has caused public health officials to urge people get vaccinated if they already haven't received the shots.
Here's a guide on whether you need to get vaccinated:
Q: When did people start getting vaccinated?
A: The measles vaccine was first introduced in the United States in 1963. Officials began recommending a second dose in 1989.
Q: Do I need a shot if I had the measles long ago?
A: No. "The people who had measles a long time ago, there's good evidence they're protected for life. The only exception to that is if they got it in the first year of life," said Dr. James Cherry, a UCLA research professor and primary editor of the Textbook of Pediatric Infectious Diseases. Virtually all people born before 1947 would have had the measles, Cherry said.
Q: What if I can't remember whether I had the measles?
A: You can get a blood test that will show if you are immune to measles. Or you can get the measles vaccine, known as MMR for measles, mumps and rubella.
Q: What's the regular schedule to get measles shots?
A: There are two. The first shot is recommended between 12 to 15 months of age, and the second between ages 4 and 6. California law requires two doses of measles shots for new kindergartners, but exemptions can be made for medical reasons or if a parent says that vaccines conflict with their personal beliefs. Infants as young as 6 months old can get the vaccine in an outbreak situation or before international travel.
Q: What if I got only one shot of the vaccine?
A: Cherry advises people who don't know if they had two shots of MMR to get the second shot.
Q: Why is it important to get two shots?
A: There's a 5% chance of vaccine failure in people who receive only one shot. The chance of failure falls to less than 1% for those who get two.
Q: If I can't remember, is it OK to get a third shot?
A: Yes, it's safe, Cherry said.
Q: Why do some people still get measles even though they received two shots?
A: In some people, the vaccine doesn't produce enough antibodies to fight off the measles virus. One reason is "waning immunity." In the 1960s and '70s, the systems of immunized people had to regularly fight off the measles virus. Practice makes perfect. But now, immune systems are out of practice and some people who got the shots in the 1960s, '70s and '80s may be more susceptible today.
Q: What is illness like if you have already been fully vaccinated?
A: In most people, it can be a weaker form of illness than in unvaccinated people, Cherry said.
Q: Have doctors or healthcare providers been overlooking measles?
A: Yes, there have been some cases, according to the California Department of Public Health. The first symptoms are similar to other illnesses, like fever, coughing, sneezing and red, watery eyes. People can have these symptoms for about four days before developing the telltale rash that begins on the head and spreads to the rest of the body. In fact, even after the rash appears, doctors might forget to consider measles.
Q: What's the latest in the measles outbreak in California?
A: There are now 80 cases in seven states and Mexico. All but 10 are California residents.