Ok guys, time for a big topic very relevant in current events - Measles! This is going to cover mostly immunization and post-exposure prophylaxis recommendations and not the clinical symptoms.
Our former clerkship director Dr. Anna Pickens has a great video summarizing all things measles available on emdocs.net:
http://www.emdocs.net/em-in-5-measles/
Scroll to the bottom for the TL;DR version.
Measles
A little bit of background first. One of the most infectious pathogens, measles was targeted for eradication in the 1960s because of its highly infectious nature and it's human-only infectivity, which led to a dramatic decrease in the number of cases in developed countries. Before this, about 90% of children acquired the virus before age 15. In the United States, the immunization program has resulted in a staggering 99% percent decrease in the number of cases. Since then, largely due to under-vaccination or unvaccinated populations, cases have been on the rise since 2008. Most of these cases are imported from abroad. Of the cases in the US, 85% of cases were unvaccinated despite being eligible for vaccination.
Measles is highly contagious and carries a 90% infectious rate when a susceptible person is exposed. Population immunity of > 95% is needed to stop ongoing transmission.
Vaccination
In the US, two doses of vaccination MMR is recommended, the first at 12-15 months (conferring 95% immunity) and a second dose at 4-6 years of age (conferring 99% immunity) or at least 28 days after the first dose.
Fun fact: vaccination is recommended no earlier than 12 months because maternal antibodies seem to interfere with seroconversion (87% seroconversion if administered at 9 months, 95% at 12 months, and 98% at 15 months).
A third dose is not routinely recommended as it is not associated with any more protection than two doses.
For those who received two doses of MMR based on the CDC recommended schedule, the CDC, NYCOH, and NYCOHMH all discourage serologic testing if the vaccine history is available.
What this means: if your patient has had two doses of MMR, they do not need titers and if they have titers, it doesn't matter!!
For those born before 1957, they are presumed to have immunity to measles and mumps. This is not the case for rubella (not covered here).
Pregnant women are at higher risk than the general public of measles related morbidity and mortality and should therefore be counseled by their ob/gyn regarding vaccination status. As with all adults, pregnant women that have evidence of two doses of MMR are considered immune and should not have titers performed. If documentation is not available, pregnant women should not receive MMR due to a theoretical risk of vertical transmission of rubella to the fetus. MMR vaccine should then be administered after delivery. That being said, studies on neonates that are born to women that have inadvertently received MMR shows no risk of of MMR vaccine to the fetus.
Healthcare workers are also considered a special population due to our frequent exposure to communicable disease. The recommendations for vaccination and testing are the same as the general public regardless of date of birth (ie. two doses or serological evidence is always required). Additionally, during outbreaks, healthcare workers without evidence of immunity should receive 2 doses MMR.
Post-Exposure
First things first: who qualifies as "being exposed to measles"? You qualify if you have shared the same air as someone while they were infectious. The infectious period lasts from 4 days before until 4 days after the onset of rash.
Un-vaccinated individuals should receive MMR vaccination within 72 hours of exposure if there are no contraindication (ie. pregnancy, immunocompromise, anaphylactic reaction to any of the vaccine components, infants < 12 months of age). Between 72 hours and 6 days of vaccination, they should receive IMIG (0.5mL/kg IM, max 15 mL).
Infants < 12 months of age exposed to measles should receive IMIG 0.5mL/kg IM, max 15 mL within 6 days of exposure.
Because of the increased risk of complications and death in pregnancy, pregnant women exposed to measles should receive IVIG 400mg/kg within 6 days of exposure. Additionally, peri-partum, pediatrics should be made aware of the potential risk of congenital measles if born to a mother with measles.
Immunocompromised individuals should also receive IVIG 400mg/kg within 6 days after exposure regardless of vaccination status.
Infants exposed to measles (< 12 months of age) should receive IMIG 0.5mL/kg (max 15 mL)
Healthcare workers who do not show evidence of immunity either by records or serological testing should receive MMR and be removed from work for 21 days following exposure. Those who do not receive MMR should be removed from work for 21 days following exposure even if they have received IMIG. If there is only one dose documented, they may remain at work and should receive a second dose.
TL;DR:
Measles very contagious, MMR has been successful in greatly decreasing cases
Most outbreaks have been due to under-vaccination or unvaccinated populations
Recommended schedule: 1st dose at 12-15 months, 2nd dose at 4-6 years or 28 days after the first dose
Titers are not necessary if there is evidence of two appropriately administered vaccinations for everyone
If record/evidence of vaccination is not available, serological testing should be performed
Post exposure:
Unvaccinated individuals should receive MMR within 72 hours of exposure or IMIG 72 hours-6 days after exposure
Infants < 12 months should receive IMIG within 6 days
Pregnant women and immunocompromised should received IVIG within 6 days
Exposed healthcare workers who do not have evidence of immunity should not return to work for 21 days following exposure regardless of whether they received MMR or IMIG.
Sources:
https://www.uptodate.com/contents/measles-mumps-and-rubella-immunization-in-adults
https://www.uptodate.com/contents/measles-mumps-and-rubella-immunization-in-infants-children-and-adolescents
https://www.health.ny.gov/prevention/immunization/toolkits/docs/health_advisory.pdf
https://www.cdc.gov/mmwr/preview/mmwrhtml/rr6007a1.htm
http://www.emdocs.net/em-in-5-measles/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4552307/
