Bottomline:
While measles is very contagious and can be severe in chronic lymphocytic leukemia (CLL), most are thought to be significantly protected by past infections or immunizations. Even for suspectable people, the risk is tiny away from the areas with outbreaks.
Background on Measles:
Measles was declared “eliminated” in the United States in 2000 due to widespread vaccination and “herd immunity.” However, we have experienced a resurgence of outbreaks, primarily attributed to declining vaccination rates in certain communities.
Recent Measles Outbreak:
As of March 10, 2025, there have been 222 cases in the US, with a significant measles outbreak in Texas and New Mexico. Sadly, this includes two deaths: an unvaccinated child in Texas and an unvaccinated adult in New Mexico. The outbreak is concentrated in Gaines County, Texas, and has impacted neighboring counties and eastern New Mexico. The affected regions include communities with lower vaccination rates, such as certain Mennonite populations.
Historical Context:
2019 Outbreak: The US experienced a significant measles outbreak in 2019, with 1,274 confirmed cases across 31 states. This was the largest number since 1992 and was primarily linked to unvaccinated individuals in Orthodox Jewish communities in New York.
For comparison, there were 285 reported cases reported in 2024, a substantial rise from the 59 documented in 2023 and higher than the number seen so far this year, but 2025 has just begun.
Measles Virus Spread:
Measles is extremely contagious, and > 90% of those suspectable who are exposed will become infected. It is a respiratory virus spread through the air. It is said to linger in the air for up to two hours after an infected individual has left the room. Even brief exposure can lead to infection.
Measles “R₀” is 12–18. This means one infected person can spread measles to 12–18 others in a susceptible population (unvaccinated with no prior infection). For comparison, the original strain of COVID-19 had an R₀ = 2-3, and the R₀ for influenza is 1.3.
Measles Symptoms:
Symptoms in Immunocompromised Individuals
- Prolonged and high fever, often persistent with slow resolution
- Severe pneumonia (viral to start but can be complicated by secondary bacterial infections. Pneumonia is the leading cause of death in measles. A cough can linger for weeks.
- Atypical rash or no rash due to impaired immune response
- Longer duration of viral shedding, increasing the risk of transmission
- Severe and prolonged diarrhea, leading to dehydration
- Hepatitis (inflammation of the liver)
- Encephalitis (brain inflammation) – Can occur without the typical rash, leading to seizures, confusion, or coma
- Subacute Sclerosing Panencephalitis (SSPE) – A rare, fatal, late complication that can occur years after infection.
Measles is immunosuppressive and may deplete immune memory cells for other infections.
Immunity and Measles Vaccine:
Natural Immunity:
Measles was extremely widespread before the vaccine became available in 1963. The CDC considers anyone born before 1957 to have had a measles infection and should have life-long immunity. This is true even with the development of CLL and small lymphocytic lymphoma (SLL) years later. Like all things in life, this is not 100%, but it is very close.
Vaccines:
The present MMR or mumps, measles, and rubella vaccine is 97-99% effective with the recommended two doses in the general population. A single dose is approximately 93% effective.
Some prior vaccines were less effective, but since 1989, two doses of MMR have been used.
The present measles vaccine is live and not considered safe for those with impaired immunity. While there is some discussion on whether it might be safe for some CLL / SLL patients with a healthy immune system, including normal counts of specific immune cells (CD4/CD8) and levels of immunoglobulin, this has not been studied, and it remains the firm recommendation of the medical community that CLL / SLL patients receive no live vaccines including MMR. However, CLL Society joins with the CDC and other health organizations in encouraging all those who are eligible and not immunocompromised to get vaccinated with MMR.
Testing, Treatment, and More:
The simple measles titer or the measles IgG antibody test checks your blood for measles antibodies to see if you’re immune. A positive test is 95% reliable in predicting one is protected. Even if antibody levels have waned, there is still probably significant cellular immunity.
For those receiving IVIG, measles antibodies should be present, though the amount of protection will vary from batch to batch. If there is a known exposure to measles and the CLL patient is susceptible, IVIG should be given within the first six days as Post-Exposure Prophylaxis (PEP) to lessen disease severity.
There is no specific antiviral therapy, and treatment is supportive. Vitamin A has been shown to probably be helpful, particularly in young children or those with deficient levels. It is not a substitute for vaccination as it provides no protection against contracting the disease.
Conclusion:
Most CLL / SLL patients are probably protected against measles to a significant extent, especially those born before 1957. While any outbreak of such a contagious disease is menacing and upsetting, as it is 100% preventable with a high vaccination rate, the risk is very low unless one is near the outbreak. IVIG PEP within six days should help due to its protective anti-measles antibodies. Unfortunately, vaccination with a live vaccine is not an option for those with CLL / SLL.
