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TEN QUESTIONS & ANSWERS ON MEASLES PROTECTION  
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Katelyn Jetelina
March 14, 2025
Your Local Epdemiologist
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_ The main thing to know: MMR vaccines are highly effective and
provide long-lasting protection. Outbreaks occur mainly among
unvaccinated individuals. But here's more about boosters, young
children, infection-induced immunity and transmission. _

Explaining the effect of vaccination on measles death rates, by Nefi
(CC BY-NC-SA 2.0)

 

With measles cases rising across the country, I’ve been getting a
lot of questions (especially after that Hannity interview yesterday)!
Here are your top 10 answered.

TL;DR: MMR vaccines are highly effective and provide long-lasting
protection. Outbreaks occur mainly among unvaccinated individuals.

1. WHAT IS “UP-TO-DATE” ON THE MEASLES VACCINE? DO I NEED A
BOOSTER?

You’re considered up to date if you:

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Have two doses of MMR or MMRV

*
Were born before 1957 (since measles was widespread then, most people
were naturally exposed and are assumed immune)

You’re very well-protected (97% 
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against measles) and do not need a booster.

An exception: If you received the inactivated measles vaccine
between 1963 AND 1967, you may need a booster. Most people at that
time received the more effective live vaccine, but if you’re unsure,
check with your healthcare provider.

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Table by YLE

Measles antibodies last a long time. Studies tracking individuals for
17 years found that most (~91%
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protective antibodies. Modeling studies
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a single dose of MMR provides protection for about 25 years—and we
get two doses, extending immunity even further. Scientists estimate
that measles antibodies have an astonishing half-life of over 3,000
years [[link removed]]. We also
have T cells and B cells (see more in #2).

Our recommendations may evolve in the future, but for now, the data
remain strong. One reason they could change is that with lower measles
exposure, our immune systems no longer receive periodic boosts from
asymptomatic infections—similar to how hybrid immunity works with
Covid-19. Only time will tell.

2. SHOULD I CHECK MY TITERS? DOES THAT HELP?

Titers measure antibodies in your blood but don’t account for T cell
and B cell immunity, which also protect you.

T cell and B cell memory are particularly important because once
measles enters your body, it doesn’t replicate that fast. It is slow
enough that if you get infected, they will start pumping out
antibodies to prevent you from getting sick. This means that a
negative result on titers does not necessarily mean you are not
protected.

The main reason to get titers would be as a matter of insurance
coverage for a booster-—some plans won’t cover the cost unless
titers to one of the MMR viruses come back negative.

Titers could also be useful for pregnant women (see more in #6).

3. IS THERE A REASON NOT TO GET A BOOSTER FOR MEASLES?

Getting a booster has very few risks.

However, unnecessary boosters could contribute to a vaccine shortage.
As explained here
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12 million doses are available in the country each year; we must
reserve these for children since they need at least two for initial
protection. This has to be the priority. Local shortages in Texas have
already been reported
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Canada ran short
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year.

4. WHY DO WE NEED JUST TWO MEASLES VACCINES WHEN WE ARE YOUNG BUT AN
ANNUAL FLU SHOT, FOR EXAMPLE?

They are just very different viruses, so tools like vaccines work
differently:

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_MUTATE DIFFERENTLY._ Measles mutates far less than flu. The measles
virus from the 1960s is virtually the same today, unlike flu, which
changes every couple months. (See this previous YLE post for more
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_INFECT DIFFERENTLY. _Measles replicates slowly and deep in the body,
giving the immune system time to act. Flu replicates quickly in the
nasal passages, making it harder for the body to stop transmission.

5. IS INFECTION-INDUCED IMMUNITY BETTER THAN VACCINE-INDUCED IMMUNITY?

Infection-induced immunity may last slightly
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but at a high cost—measles can lead to severe complications,
including pneumonia, encephalitis, and death.

The vaccine also offers strong, long-lasting protection. It’s a live
virus vaccine, so it’s a tiny, controlled version of the infection
for all intents and purposes—but with far fewer risks. If I were to
bet on it, I would rather have the odds on the right than the left.

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Source: New York Times

6. IS A BABY PROTECTED IF THEIR MOM WAS FULLY VACCINATED?

The vast majority
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moms transfer antibodies to their fetuses. (Moms’ bodies are pretty
amazing!) Once born, antibodies wane quickly and are almost all gone
at 6-12 months of age.

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Source; International Journal of Infectious Diseases
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Breastfeeding may provide some protection, but it is not a substitute
for vaccination. The role of breastmilk antibodies in the protection
from measles is possible, but there is a lack of robust supporting
evidence.

Anyone trying to conceive should have MMR titers checked, and if
levels are low, MMR should be administered 28 or more
days _before_ _conception_.

7. WHY WAIT UNTIL 12 MONTHS TO GET CHILDREN VACCINATED?

We try to find the sweet spot by balancing a few factors:

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Maternal antibodies waning

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Maturity of the immune system

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The most common age of infection

That said, if there is a measles outbreak, young children need
protection as soon as possible. Early vaccination is one provisional
measure
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can take starting at 6 months. This early dose does not count toward
the two-dose series, which will be needed at 12 months.

8. CAN I GET MEASLES IF I’M FULLY VACCINATED?

The MMR vaccine works incredibly well—you’re 35 times
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measles than someone with no immunity.

However, no vaccine is perfect. A breakthrough case is rare but
possible (3 out of 100
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will get infected), but the illness is typically mild
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We don’t know _why_ there are breakthrough cases, but there are
two possibilities:

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_WANING IMMUNITY_, or

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_VACCINE DIDN’T WORK IN THE FIRST PLACE FOR WHATEVER REASON_. ~7%
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protection after the first dose, but, of those, 95% will be fully
protected after a second dose. Only a small percentage of people
don’t respond to both doses.

9. IF I AM EXPOSED, CAN I TRANSMIT MEASLES?

Transmission after vaccination, especially if you’re asymptomatic,
is rare:

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_WE SEE THIS IN THE LAB DATA_. A small study
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no viral shedding among asymptomatic or mildly ill patients. However,
this is a very old study, and we need
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replicate its findings with more sensitive lab equipment.

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_WE SEE THIS IN THE EPIDEMIOLOGICAL DATA._ While several
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spread among vaccinated people, especially after intense or prolonged
exposure, it’s limited.

A 2011 New York outbreak was the first documented case
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vaccinated person spreading measles. Out of 88 close contacts, only 4
got infected—and none of their contacts got sick. We would have
expected a ~90% infection rate if this had been an unvaccinated case.

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Source: YLE

10. DO WE HAVE TO WAIT FOR MY CHILD TO BE 4 YEARS OLD FOR A SECOND MMR
DOSE?

The second MMR dose can be given 28 days after the first—unless
it’s the MMRV vaccine, which requires a 3-month gap.

This flexibility is especially useful in outbreak areas. Healthcare
providers may recommend
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second dose earlier for children aged 1 to 4 who live in or are
visiting outbreak areas.

Longer intervals between doses generally strengthens immunity, making
some worry that shortening the measles vaccine interval could weaken
protection. However, data suggest timing isn’t a major factor in
long-term immunity, as long as the first dose doesn’t interfere with
the second (requiring at least 4 weeks between them).

The second dose, typically given at ages 4-6, ensures protection
before school, where measles spreads easily. It’s not technically a
booster, but it helps cover the 7% of people who don’t respond to
the first dose. Without it, gaps in immunity can fuel outbreaks.

BOTTOM LINE

If you’re fully vaccinated, you can be confident in your protection.
We continue to follow the data, but failure to vaccinate still plays
the biggest role in measles in the United States compared to vaccine
failures.

If you have specific questions, be sure to bring them up with your
physician.

Love, YLE

_Big thanks to Edward Nirenburg and Dr. David Higgins for helping me
wade through a lot of this science and recommendations._

_Your Local Epidemiologist 
[[link removed]](YLE) is founded and operated
by Dr. Katelyn Jetelina, MPH PhD—an epidemiologist, wife, and mom of
two little girls. Dr. Jetelina is also a senior scientific consultant
to a number of non-profit organizations. YLE reaches over 340,000
people in over 132 countries with one goal: “Translate” the
ever-evolving public health science so that people will be
well-equipped to make evidence-based decisions. This newsletter is
free to everyone, thanks to the generous support of fellow YLE
community members. To support the effort, subscribe or upgrade
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* vaccines
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* measles
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* infectious diseases
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* Science
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