The Kids

Does Breast-Feeding Protect My Baby From Measles?

Answers for understandably freaked-out parents of unvaccinated infants.

mother breastfeeding baby.
Will breast-feeding keep my baby from getting measles?

Photo illustration by Slate. Photo by Thinkstock.

A few days ago, a doctor told an acquaintance of mine that, in light of the ongoing measles outbreak, he would never take an infant on an airplane. As a mother who plans to take her 7-month-old across the country next month, I was not pleased to hear his advice. My first reaction was: That’s insane! But, as nearly 1 out of every 3 children under the age of 5 who catches measles ends up in the hospital, how worried should parents of as-yet-unvaccinated infants be? And what can parents do, if anything, to keep their babies safe? Here are some answers.

Is the outbreak really that bad?

It’s pretty bad. So far this year, 121 measles cases have been reported in 17 states and Washington, D.C., which means we are on track to beat last year’s numbers, when we had the most U.S. measles cases in 20 years. The 121 number may not seem like a lot, but with measles, cases can multiply quickly. That’s because the virus is wildly contagious. In an unvaccinated community, each measles-infected person will infect, on average, 12 to 18 other people. Each person infected with the flu, by contrast, only infects one or two others.

With a virus as contagious as measles, more than 95 percent of individuals in a community may need to be vaccinated to prevent an outbreak. As of 2013, there were 17 U.S. states where fewer than 90 percent of children 19 to 35 months old had received a dose of measles, mumps and rubella, or MMR, vaccine. This means that measles may be able to spread quickly in many pockets of the U.S., and among those most at risk for catching the infection and getting really sick are infants, who typically do not receive their first doses of MMR until 12 months of age.

How likely is it that my baby will catch the measles?

The risk posed to you and your family largely depends on where you live. If your community has not seen any measles cases, you and your kids are at a much lower risk than if you live in, say, Orange County, California, where 34 residents have come down with measles so far this year. (If you don’t know how bad things are in your region, check with your state or local health department.) If your local community has had measles cases, your baby will be more at risk if she goes to day care or spends a lot of time in public places. The measles virus can live for two hours on a surface or suspended in the air.

Also important is the percentage of your community members who have been vaccinated against measles. That’s because, again, in the event that measles does end up in your neighborhood (or in your kid’s school), it will spread much, much more quickly if there are a lot of unvaccinated individuals around. Vaccination rates can vary widely in the same state because nonvaccinating parents tend to cluster together, so looking at state vaccination rates may tell you very little about coverage where you live. If you have older kids, check their schools’ vaccination rates; this USA Today database includes school rates from 13 states. The presence of just one kid with measles in a school—and keep in mind, kids can be contagious four days before they get the rash—could cause an outbreak if fewer than 19 out of every 20 students and teachers are vaccinated. In day cares that care for babies and toddlers, outbreaks are even more likely, since infants aren’t yet immunized and toddlers have only had one dose of MMR. This is why five babies caught the measles at a day care in Palatine, Illinois, last week. (Although not all states require day care centers to disclose vaccination rates to inquiring parents, California parents can actually find this information online.)

How can I keep my baby safe if people have measles near where I live?

If you know measles is close by and your baby is at least 6 months old, you can ask your pediatrician for an early MMR shot. They don’t “take” as well as MMRs given later, so your baby will still need another dose at 12 months, but these early shots can provide some protection. Also, “avoid crowded areas if you can,” says Stanford University pediatric infectious disease specialist David Hong. And make sure you’re protected. (See next question.)

Do I, as a parent, need another MMR shot?

It depends. Many of the individuals who have caught and spread measles in this outbreak have been adults, so it is important that you are immune. If you haven’t been vaccinated but you have either had measles in the past or you were born before 1957, you’re not considered to be at risk for catching it now. Between 1963 and 1967, several vaccine types were being administered, and people who received the inactivated form of the vaccine during those years or don’t know what type they got should consider getting vaccinated again. (The inactivated form didn’t work as well as the current live-attenuated vaccine.)

If you were vaccinated with MMR after 1967 but before 1989, you may have only received one dose of the live-attenuated vaccine; if so, you can ask your doctor for another dose. But unless you’re a health care worker, a college student, or you travel internationally a lot, you probably don’t need to get another shot. That’s because in 95 out of every 100 people, the first dose of the MMR vaccine will still prevent infection (two doses will protect 99 out of 100 people). Still, if you’re concerned, you can ask your doctor for a measles antibody test or just get another shot; getting an extra dose does not pose any risks, although you should not get one if you’re pregnant or may get pregnant within four weeks of receiving it. If you were vaccinated after 1989, you likely received two doses of the live attenuated vaccine, and if so, you’re fine. Man, keeping millions of people healthy is complicated!

So. Should I really not take my baby on an airplane?

“This is a tough one,” Hong says. “Certainly kids under 1 year are the most vulnerable, but at the same time, it’s hard for me to feed into the fear.” Although the outbreak is bad, he explains, measles is not right now close to becoming endemic—meaning that measles transmission is not likely to continue uninterrupted here in the U.S. once this outbreak is over. (There may be additional outbreaks this year, but they will likely start because measles is brought into the U.S. by international travelers. That said, if vaccination rates drop further in the U.S., measles could become endemic again.) Ultimately, Hong says, “the recommendation to avoid flying seems a bit excessive to me.” Plus, the risk of exposure is the same in any public place—a mall, a plane, an amusement park. So if you start advising parents not to take infants on planes, you might as well tell them never to leave their houses, and that’s overkill.

You should, however, take more precautions if you’re going to be traveling with your infant internationally. For a while now, the Centers for Disease Control and Prevention has recommended that babies over the age of 6 months get a dose of MMR vaccine before traveling internationally, since measles is endemic in many countries in Europe, Asia, the Pacific, and Africa. If your baby is too young for the shot, you may not want to travel to a measles-endemic country.

I heard that a newborn is protected by his or her mother’s antibodies. Is that true?

Yes: A mom who has been vaccinated or who had measles at some point in her life passes protective antibodies to her fetus via the placenta—so much so that the baby’s blood concentration of these antibodies at birth often exceeds her mother’s. (Premature babies don’t get as much protection because most antibodies are transferred in the last four weeks of pregnancy.)

A full-term infant is typically protected against measles for about a month after birth if her mom has been vaccinated against measles, and she is protected for a little longer if her mom actually had the measles. But once these maternal antibodies break down, a baby is vulnerable until several weeks after she gets her first MMR shot.

What about breast-feeding? Will that keep my baby from getting measles?

Nope. The types of antibodies that are passed from mom to baby through the placenta are called immunoglobulin G, or IgG, antibodies, and these circulate in the blood and play a big role in protecting against measles. The antibodies that babies get through breast milk, on the other hand, are IgA antibodies, which primarily protect against diseases that affect the gut, such as diarrheal infections. “Although we encourage breast-feeding, I’m not aware of any specific protective benefit of breast-feeding when it comes to measles infection,” Hong says.

So what’s the bottom line for parents of infants?

Make sure you and any older kids are up-to-date with vaccinations, and keep on top of what’s happening where you live. If there are measles cases nearby, and especially if you suspect vaccine coverage might be low in your community, keep your baby out of public places and consider asking your pediatrician for an early MMR shot. Early symptoms of measles include high fever; cough; runny nose; and red, watery eyes. If you suspect your child might have it, call your pediatrician first—don’t just drop in—and find out what you should do.

Chances are, based on the numbers, your baby will stay healthy. And perhaps this measles scare will encourage on-the-fence parents to vaccinate their kids so that outbreaks like this become a thing of the past. A mom can dream, right?

In addition to the sources mentioned, The Kids would like to thank Jessica Atwell from the Johns Hopkins Bloomberg School of Public Health and Julie Boom from the Texas Children’s Hospital.