Any area can be affected by measles. My county is in the middle of an measles outbreak right now. This is despite relatively high MMR vaccine rates above 95% for at least 1 MMR by 3 years of age. There are a lot of questions about measles outbreaks, so I thought I’d tackle a few. Like most pediatricians, I’ve never seen measles and I hope to not miss it if I do. We all need to be aware of its symptoms so we can recognize it when we see it!
What is measles?
Measles is a viral illness that includes fever, cough, fatigue, red eyes, and a characteristic rash. The rash spreads from head to trunk to lower extremities.
One rare complication of measles infection that occurs many years after the illness appears to resolve is subacute sclerosing panencephalitis (SSPE). It is a fatal disease of the central nervous system that usually develops 7–10 years after infection.
What is the timeline of symptoms after exposure?
Measles is highly infectious. It is primarily transmitted by large respiratory droplets in the air, so handwashing doesn’t help prevent exposure.
An area remains at risk for up to 2 hours after a person with measles was there. This is why it is IMPERATIVE that you should not leave your house if you suspect you have measles until you have spoken with the health department or your physician. DO NOT go to a walk in clinic or your doctor’s office unannounced. You will need to make arrangements to meet someone outside and wear a mask into the building. You will be put in a special negative pressure room, which is not available in most clinics.
More than 90% of susceptible people develop measles when they’re exposed.
The average incubation period for measles is 11–12 days. It takes 7–21 days for the rash to show. It is due to this long time for the characteristic rash that susceptible people who were exposed are put in isolation for up to 21 days.
Most people are contagious from about 4 days before they show the rash until 4 days after the rash develops. If a person has measles and the rash resolves, they can leave isolation when cleared by their physician and/or the health department.
What is a measles outbreak?
Measles outbreaks are defined as 3 or more measles cases linked in time and space.
How do outbreaks start?
I know the big question on everyone’s mind during an outbreak is, “Where did it start?”
Often an unimmunized traveler brings the measles virus into the US. Countries in Europe, Africa, Asia, and the Pacific continue to have outbreaks. Travelers who visit those countries can return to the US and share the virus for a few days before symptoms are recognized. Anyone who was in the same area as an infected person for up to 2 hours after that person left the area could be exposed.
In case you’ve heard that vaccines can lead to outbreaks: that’s not the case. Measles shedding from the MMR does not cause disease.
What happens during an outbreak?
During an identified outbreak of any reportable infectious disease, the health department directs what to do. They attempt to identify and notify all people who are at risk.
Our current outbreak involves several infants from the same unnamed daycare in addition to people not associated with the daycare. I know many families are worried that their child was at that daycare. Families at that daycare will have been notified by the health department already. The health department will track all known contacts of those families.
Local health departments also will notify the public of known locations of potential contact with the virus. The above linked article lists the known locations that infected people visited during their contagious period.
Why are infants at risk?
Infants are at particular risk because they are not typically vaccinated against measles until 1 year of age.
When the virus is in a setting with infants, such as a daycare, it can easily spread.
Infants under 2 years of age who are infected also tend to have more complications from the disease than older children and adults. This is one of the biggest reasons to not wait until 2 years to start immunizations, as some anti-vaccine groups suggest.
If you think you were exposed to or have symptoms of measles
It is IMPERATIVE that you should not leave your house if you suspect you have measles until you have spoken with the health department or your physician.
DO NOT go to a walk in clinic or your doctor’s office unannounced.
You will need to make arrangements to meet someone outside and wear a mask into the building. You will be put in a special negative pressure room, which is not available in most clinics.
Do not go to the pharmacy to pick up medications. Don’t go to the grocery store for food.
Do not leave your home unless it is to a medical facility that knows you’re coming and is prepared.
(Yes, I know I repeated myself for much of this section, but it’s that important!)
The MMR vaccine can help stop the spread
The MMR vaccine is recommended routinely at 12-15 months and again at 4-6 years of age. Vaccines not only help the vaccinated, but provide herd immunity to those too young to be immunized and to those who are immunocompromised.
Please be sure your family is up to date on all their vaccines. All children over 1 year of age should have at least 1 MMR vaccine. All school aged children and adults should have 2 MMRs. By vaccinating your family, you not only protect them, but also those around you!
Why is a second dose given?
The second dose is used to provide immunity to the approximately 5% of people who did not develop immunity with the first dose. It is not a booster because it doesn’t boost the effect of the first dose.
The second MMR helps some people develop immunity if the first vaccine did not work effectively.
This second dose can be given as early as 28 days after the first.
Why don’t we start the vaccine series earlier?
Many parents worry that we don’t give live virus vaccines to infants because they’re less safe, but that’s not why at all.
Maternal antibodies (fighter cells from mom that got into baby during pregnancy) can inhibit the body from being able to build its own antibodies well against a vaccine.
Maternal antibodies are good because as long as they’re in the baby’s body, they fight off germs and protect the infant! They tend to hang around for the first 6-12 months of life.
If a disease has a low incidence, it is acceptable to let the maternal antibodies do their job for the first year.
By the first birthday most maternal antibodies have left the infant, so a vaccine can be used to build the baby’s immunity.
Sometimes we do vaccinate earlier
If there is a high risk of exposure it is recommended to give the vaccine as early as 6 months in case the maternal antibodies are already too low for infant protection.
Many parts of the world have high measles rates so fit into this recommendation. When infants between 6 and 12 months travel internationally, they should receive one dose of MMR vaccine prior to travel.
Sometimes during US outbreaks it is recommended to vaccinate infants 6-12 months. The local health department helps to determine which infants should be immunized in this situation.
If the maternal antibody levels are still high in the infant, the vaccine won’t work. In this situation the baby should still be protected against the disease from mom’s antibodies. That is why this early vaccine does not “count” toward the two needed after the first birthday.
At some point the maternal antibodies go away, we just don’t know when exactly, so the baby who gets the MMR early needs another dose after his first birthday to be sure he’s making his own antibodies once mom’s go away. This dose after the birthday is the first that “counts” toward the two MMRs that are needed.
The next dose of MMR can be anytime at least 28 days after the first counted dose, but we traditionally give it between 4-6 years with the kindergarten shots.
What if someone who hasn’t been vaccinated is exposed?
The MMR vaccine may be effective if given within the first 3 days (72 hours) after exposure to measles. This is why the local health department is so aggressive in identifying cases during an outbreak.
Immune globulin (IGIM, a type of immunity that doesn’t require a person to make their own immunity) may be effective for as long as 6 days after exposure. IGIM should be given to all infants younger than 6-12 months who have been exposed to measles. The MMR vaccine can be given instead of IGIM to infants age 6 through 11 months, if it can be given within 72 hours of exposure.
Are boosters of the MMR needed?
Those of us who work in healthcare must have titers checked to verify immunity to many of the vaccine preventable diseases.
Healthcare workers come into contact with sick patients and patients with weak immune systems, so this is one way to help control disease spread.
From Immunize.org:
| Adults with no evidence of immunity (defined as documented receipt of 1 dose [2 doses 4 weeks apart if high risk] of live measles virus-containing vaccine, laboratory evidence of immunity or laboratory confirmation of disease, or birth before 1957) should get 1 dose of MMR unless the adult is in a high-risk group. High-risk people need 2 doses and include healthcare personnel, international travelers, students at post-high school educational institutions, people exposed to measles in an outbreak setting, and those previously vaccinated with killed measles vaccine or with an unknown type of measles vaccine during 1963 through 1967. |
Most people don’t know their immune status, and it’s not recommended at this time to check it for the general population.
During an outbreak exposed people might be asked to be tested to help identify risk factors and track disease patterns.
