Many People With Cancer Lack Protection Against Measles and Mumps

 In one of the first studies of its kind in recent decades, a team of researchers has discovered that a high percentage of people with cancer lack protection against measles and mumps. In an era when measles is resurfacing after being eradicated in the U.S. and the COVID-19 pandemic is delaying some children's vaccine schedules, this finding raises questions about the level of threat to cancer patients.

Measles is "hands-down one of the most infectious viruses” in today's world, said Dr. Steven Pergam, an infectious disease researcher at the Fred Hutchinson Cancer Research Center and a medical professor at the University of Washington. A person with measles can infect 12 to 18 unvaccinated people on average, whereas that range is 2 to 3.5 for the original strain of SARS-CoV-2 and 6 to 8 for the delta variant, Pergam said. A person with mumps can infect an average of 10 to 12 unvaccinated people.

The vaccine against measles, first tested in 1958, prevents disease circulation extremely well. It is often administered in combination with mumps and rubella vaccines in what is known as the MMR vaccine. Even though the MMR vaccine provides great protection against these serious illnesses, the vaccination rates have fallen, especially in certain communities, which has led to measles outbreaks in states such as New York, Minnesota and Washington in recent years.

To learn more about how these outbreaks could affect people with cancer, Pergam and his co-workers analyzed blood samples of the cancer patients who visited Seattle Cancer Care Alliance or Fred Hutch for appointments in a five-day period in August 2019. After analyzing 959 samples, the team discovered that 25% of the people with cancer lacked protective antibodies for measles and 38% lacked antibodies against mumps. These percentages are higher than the percentage for the general U.S. population, which was 4% for measles between 1999 and 2004, according to a study published in The Journal of Infectious Diseases.

Further analysis by the team revealed that younger patients between ages 30 and 59, patients with blood cancer, and cancer patients who received stem cell transplants were even less protected than the rest of the patient groups. The team published the results in the journal JAMA Network Open in July.

Pergam said the lower protection level for people with cancer is due to a combination of factors. Because blood cancers such as leukemia directly damage one's immune system, patients are less able to produce protective antibodies. Similarly, patients who receive bone marrow transplants lose their protective antibodies in the years after the transplant. 

Cancers in younger patients are more often blood cancer, which could explain the age trend, Pergam said. However, Elizabeth Krantz, a statistician at Fred Hutch and one of the authors of the paper, said that even after the relationships between the patients' ages and cancer types were detangled statistically, younger patients still showed lower protection.

One reason could be that older patients, who survived the era when measles and mumps were more common and routinely killed hundreds of people each year, may have caught the diseases and recovered. In the case of measles and mumps, the immunity that develops due to a real infection could be stronger than the immunity generated by the vaccine. 

Another reason could be that growing vaccine hesitancy resulted in some young people in the study lacking any protection that might be conferred either by a vaccine or a natural infection, Pergam said, although that's hard to prove.

"Measles is something that's sneaking around in the background," Pergam said, "and we need to be ready because we do think that rates of vaccine are dropping." A recent federal health report that studied 10 U.S. states said the MMR vaccination rates dropped about 22% for babies younger than 2 years old and about 63% for children between ages 2 and 8 early in the COVID-19 pandemic, compared to the same time periods between March and May in 2019 and 2018. 

It is not possible for a person with cancer to receive another MMR shot because it is a live-virus vaccine that could put their health at risk, Pergam said. To protect those who are vulnerable, our society needs to step up to reach the herd immunity level. "That means everyone needs to do their part," Pergam said. "Everyone needs to step forward, everyone needs to be caught up on their vaccines so that we don't have large outbreaks."

Source: Inside Science