Buzz
We are on pace for a record-breaking measles season. Go USA!
Although the disease was largely wiped out in the U.S. by 2000, small outbreaks triggered by travelers have resulted in a few cases each year. With this year's case count surpassing 600, you might be wondering: can I rely on my childhood measles vaccine? Did I even receive it?
Children should receive a measles vaccine shot (usually as part of the MMR, which covers measles, mumps, and rubella) shortly after turning one. Some children’s immune systems might not fully respond at that age, meaning the vaccine may not be effective, which is why a booster shot is recommended when they begin kindergarten.
Why Your Previous Vaccine Might Not Be Sufficient
The measles vaccine became available in 1963, and initially, there were two types of vaccines. The version with live, weakened measles virus is still in use today, while another version with killed virus was introduced around the same time but discontinued in 1967 due to its lower effectiveness.
If you received the less effective vaccine, the current recommendation is to get a second dose using the live vaccine. (You might have already received this booster as a child.)
In 1989, the CDC began advising that even those who received the regular vaccine should get a second dose. This is because the first dose isn't effective for everyone. One dose is 93% effective, and with both doses, effectiveness increases to 97%.
How to Determine If You Need a New Dose
As mentioned previously, you can always check your vaccination history (if you can locate it), and when unsure, consult your doctor for guidance. In most cases, they will suggest what the CDC recommends: ensuring you’ve received at least one dose of the live vaccine, and in some instances, they may recommend two. Here's the CDC's breakdown:
You don’t need a vaccine if...
You’ve had measles in the past
You were born before 1957 (back then, everybody caught measles)
You’ve had a lab test confirming immunity to measles
If you're certain you've had one dose of the measles/MMR vaccine on schedule, it’s enough if...
You’re a preschool-aged child (because you’ll get the second dose when you start school)
You’re an adult with a low risk of measles exposure
You should get a second dose if:
You’re of school age
You’re an adult who travels, works in healthcare, attends college, or is otherwise at high risk of exposure to measles
If you're unsure of your vaccination status, go ahead and get the shot. The CDC states that there is 'no harm in receiving another dose of the MMR, even if you are already immune to measles.'
The above guidance applies to most people, but there are some exceptions. If you are pregnant, or if you or a family member have a compromised immune system due to an immune disorder or chemotherapy, the vaccine may pose risks that outweigh its benefits. (The CDC’s full list of contraindications is here.) However, don’t make assumptions—consult with your doctor to determine what’s best for you.
