Measles is a condition many of us learned about in school but never anticipated having to manage firsthand. The return of measles is a public health nightmare marked by high transmissibility and potential complications, including pneumonia, encephalitis, permanent brain damage, and pregnancy complications. The resurgence underscores the critical importance of vigilance, vaccination, and timely diagnosis. As of April 17, 2025, a total of 800 confirmed measles cases were reported by 25 jurisdictions in the United States alone. For this week’s EBM Focus article, we are serving up evidence-based answers to frequently asked questions about measles to help inform your practice.
1. What are the symptoms of measles you should be looking for?
The maculopapular measles rash can be dramatic, but the prodrome of fever and the 3 C’s (cough, coryza, conjunctivitis) that presents about 7-14 days after initial infection but before the rash is easy to miss. Of course, these common symptoms can be found in many diseases, alas the public health nightmare. Koplik spots (often white or yellow spots on the inner cheeks) are a little more specific but aren’t always obvious at first glance. Suspect measles primarily in unvaccinated patients with a febrile rash illness presenting after any potential exposure (including international travel, travel to current outbreak locations, exposure to travelers, or during a local epidemic).
2. What precautions should we take when seeing patients with suspected or confirmed measles infection?
Full airborne precautions (including isolation when possible) are in order when caring for patients with a confirmed or suspected measles infection. Regardless of immunity, health care professionals should use respiratory protection at least as protective as a fit-tested, NIOSH-certified disposable N95 filtering facepiece respirator upon entry into the room or care area. A respirator should be used in the context of a complete respiratory protection program. Of note, in a 2016 outbreak, symptomatic measles occurred in multiple health care workers considered immune who were exposed to symptomatic patients. (Immunity seems to reduce the severity of infection and infectivity but does not seem to absolutely prevent infection.)
3. If you suspect measles, what test should you order?
While a clinical diagnosis can be made based on symptoms, patients with previous vaccination or immunocompromise may not present classically. The most commonly used confirmatory test is a reverse transcriptase-PCR from either throat, nasal, or nasopharyngeal swabs or urine, blood, and oral fluid. PCR is most sensitive within 3 days of rash onset, but don’t wait for results to act—notify public health and start containment the moment your spidey senses tingle.
4. Is there any value in checking titers for diagnosis?
Consider testing for both IgG and IgM levels on presentation, with repeat sampling 2-3 weeks after the initial presentation if the initial serology is not diagnostic. If the initial IgM is negative, a 4-fold rise in IgG titers in 2-3 weeks is considered diagnostic. Serum specimens are the diagnostic standard, but cerebrospinal fluid may be tested when encephalitis is suspected. Oral fluid and dried blood samples are less common specimen types. Note that IgM testing can yield false positives, especially if rubella or parvovirus are in the picture.
5. Should you be checking vaccine titers?
If a patient has a documented history of 2 doses of the MMR vaccine, an MMR immunity profile (IgG) is usually not needed. If vaccination history is unclear, a measles titer can help determine immune status. A measles vaccine titer level of 120 milliunits/mL or higher generally indicates protection against the virus. Most health care systems have protocols in place that balance efficacy and cost in some way, with many recommending revaccination rather than checking immune titers if there is uncertainty.
6. Are there any medical treatments for measles?
Disease control largely depends on prevention. There are no specific antiviral therapies currently available, and the mainstay of treatment is supportive care. High-dose vitamin A administration for children with severe measles has been reported to reduce mortality. But, understand that too much of a good thing can be toxic, in this case to the liver, and avoid circulating myths that vitamin A can prevent illness—it doesn’t. Vitamin A is given in 2 doses, 24 hours apart. Recommended doses by age are as follows:
- Children < 6 months old: 50,000 units/day orally for 2 days
- Children aged 6-11 months: 100,000 units/day orally for 2 days
- Children ≥ 12 months old and adults: 200,000 units/day orally for 2 days
Antibiotics may be indicated in patients with measles who show clinical symptoms of bacterial secondary infections such as pneumonia or otitis media.
7. What are the real chances of getting measles if you are vaccinated and if you are unvaccinated?
Measles isn’t just infectious—it's one of the most transmissible pathogens encountered in clinical practice. It’s primarily transmitted by large respiratory droplets, but some small aerosol particle transmission can occur, with the virus surviving for up to 2 hours suspended in air after a contagious person has left that space. The infectious period lasts from about 4 days before rash onset to 4 days after. 9 out of 10 unimmunized children exposed to the measles virus will contract it. Complications of measles can occur in anyone, including in healthy children and adults. The MMR vaccine is a live vaccine, and it creates lasting protection in about 97% of those who receive the full series. Still, secondary vaccine failure has been reported in 2%-10% of vaccinated persons.
8. Who should be revaccinated for measles?
The recommended measles vaccine schedule begins at age 12-15 months and is followed by a booster at age 4-6 years. Unfortunately, the best immunity can sometimes ghost us. Those vaccinated prior to 1968 with either an inactivated measles vaccine or a measles vaccine of unknown type should be revaccinated with at least 1 dose of the live attenuated measles vaccine. For patients exposed to measles with an incomplete vaccine series, revaccinate within 72 hours of exposure.
9. Is there any benefit to postexposure prophylaxis (PEP)?
If you have an unvaccinated patient ≥ 12 months old who was exposed to measles, you have a 72-hour window in which the MMR vaccine may be effective as PEP. Although the evidence is limited, PEP may be more effective in limited-contact settings such as schools, child care, and medical offices compared to settings with intense, prolonged, close contact.
10. Can the MMR vaccine be administered to high-risk groups such as pregnant patients, infants < 12 months old, or those with immunocompromise?
The MMR vaccine should typically be avoided during pregnancy, before age 1 year, and in people who are immunocompromised. For infants aged 6-11 months traveling internationally, give 1 dose prior to departure, and revaccinate with a 2-dose series at age 12-15 months. For high-risk patients who have been exposed to measles but have not been previously vaccinated, immunoglobulin within 6 days of exposure can be considered.
For more information, see the topic Measles in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Rich Lamkin, MPH, MPAS, PA-C, Clinical Writer at DynaMed. Edited by Alan Ehrlich, MD, FAAFP, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Katharine DeGeorge, MD, MS, Senior Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia; Dan Randall, MD, MPH, FACP, Senior Deputy Editor at DynaMed; McKenzie Ferguson, PharmD, BCPS, Senior Clinical Writer at DynaMed; Matthew Lavoie, Senior Medical Copyeditor, BA, at DynaMed; Hannah Ekeh, MA, Senior Associate Editor II at DynaMed; and Jennifer Wallace, BA, Senior Associate Editor at DynaMed.