Long before COVID-19 burst into the world, there was another viral disease that topped Dr. Steven Pergam’s list of worries: measles.
A new study underscores his reasons for concern.
To find out how much protection cancer patients have against measles and mumps, the Fred Hutchinson Cancer Research Center physician-scientist, along with his Hutch biostatistician colleague Elizabeth Krantz, led a project in 2019 to assess the levels of antibody protection against those viruses in that population.
The results, reported in a paper published today in JAMA Network Open, are not reassuring.
“We found one in four cancer patients tested lacked protective antibodies for measles, and it was more than one in three for mumps,” said Krantz.
The research was carried out at Seattle Cancer Care Alliance, where Pergam is director of infection prevention. He and his colleagues know that measles is far more contagious than SARS-CoV-2, and should an outbreak occur it would pose a serious threat to cancer patients.
While childhood vaccinations once nearly eliminated measles as threat in the United States, rare outbreaks of severe measles in cancer hospitals in the 1980s caused fatality rates as high as 70%.
“Patients need to be vigilant and remember that other vaccine preventable diseases remain a risk in our communities,” Pergam said. “Caregivers and family members should check their status and make sure they are up to date on all their vaccines.”
Before SARS-CoV-2 vaccines became available, estimates were that each infected COVID-19 patient might transmit it to 2.5 others; in measles, estimates vary widely, but that virus’ comparable “basic reproduction number” is often set at 12-18.
“It’s the prototypical airborne virus,” Pergam said. “There are cases where people with measles have been in an exam room and left it. Over an hour later, another patient comes in and acquires measles from that room. It’s just incredibly infectious.”
In recent years, childhood vaccination rates for measles, mumps and rubella have been dipping in parts of the country, even as new treatments are helping many cancer patients survive. The MMR vaccine itself has been the target of a sustained campaign by those who reject vaccines as public health interventions. By 2019, outbreaks of measles — an entirely preventable infectious disease — were popping up, even in Washington state.
In August 2019, Pergam, Krantz and their colleagues conducted their study during five consecutive days among patients who were visiting SCCA for daytime checkups or treatments. In that week, portions of those patients’ blood samples, routinely drawn as part of their cancer evaluations, were tested for antibodies to measles and mumps.
That effort yielded antibody results from 959 patients. In addition to finding low levels of protection against measles and mumps in the group, the study also found that levels of antibodies against those viruses varied significantly by age, cancer type and treatments.
Protective antibodies against measles were most prevalent among older patients — as high as 95% among those 80 and older; and protection was lowest among those aged 30-39, where only half had such protection. The reason for this, researchers said, is likely related to those older patients having developed actual measles as children. In the case of measles, exposure to the virus provides more lasting protection than the vaccine — though that long-term protection comes at the cost of exposure to a disease that can be deadly or debilitating to children.
The tests for mumps antibodies showed even lower levels, with 38% of patients in the study lacking protective antibodies. That was less surprising because the mumps vaccine is considered less effective to begin with. Mumps is less contagious than measles, but it can also have serious health effects such as deafness and higher risk of infertility for males. Its role in causing complications in cancer patients is unknown.
The researchers noted that measles antibody protection was better among patients with solid tumors (83%) than among those with blood cancers (63%); and those who had undergone bone marrow or blood stem cell transplantations had lower concentrations of measles antibodies in their blood, with only 46% of them having protective levels.
“Blood cancers are diseases that directly effect the immune system,” Pergam said. “In those with these diseases, responses to vaccines are known to be substantially decreased, by both the cancer and the treatment itself.”
Although childhood immunizations have been responsible for limiting outbreaks of measles, COVID-19 is casting a shadow over that public health achievement.
“Households have stopped going to doctor’s appointments, and we’ve stopped sending people out into the field to vaccinate children. My worry is that measles outbreaks are going to happen throughout the world because we have not addressed this, or put resources into it,” Pergam said.
“We are setting ourselves up for multiple outbreaks throughout the country for measles if we don’t focus on getting these children vaccinated,” he added. “Mumps and measles outbreaks are potentially something that will be in our future if we don’t focus on assuring high rates of vaccination in our communities. Cancer centers need to be ready as well, as our data indicate they are places ripe for clustering and outbreaks. We must advocate for improving vaccine rates — building community immunity — to protect our patients.”
Biostatisticians like Krantz drill down deeper into the data in studies like this one, and they can find nuances that give clinicians some perspective on the data. A careful analysis of the data, she said, suggests that both age and type of cancer are likely important factors in measles and mumps immunity.
For example, Krantz notes, the lower rates of antibody protection among young people in this study could have been related to the kinds of cancers young people are more likely to have. Because solid tumor cancers are more prevalent in older people, “the younger patients in the study were more likely to have hematologic malignancies,” or blood cancers, she said.
And she noted that SCCA has a higher number of blood cancer patients than comparable institutions because the cancer hospital is particularly well known for its treatments of leukemias and lymphomas through bone marrow transplants and other therapies.
Krantz stressed that the study provides information to clinicians that wasn’t readily available before.
“Our findings really emphasize the need to increase immunity at the community level, particularly among health care workers or caregivers who have frequent contact with cancer patients, in order to protect this vulnerable population,” she said.
Sabin Russell is a staff writer at Fred Hutchinson Cancer Center. For two decades he covered medical science, global health and health care economics for the San Francisco Chronicle, and wrote extensively about infectious diseases, including HIV/AIDS. He was a Knight Science Journalism Fellow at MIT, and a freelance writer for the New York Times and Health Affairs. Reach him at firstname.lastname@example.org.
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