August 1996
ATLANTA — An unusual case of measles pneumonitis is raising questions about the safety of vaccinating people with HIV against measles.
Although the measles vaccine is live, it is recommended for individuals known to be infected with HIV. Measles has been reported with a 40% case fatality rate in patients with AIDS; limited studies have revealed no unusual or serious adverse events related to the vaccine. So, it makes sense to vaccinate them against the disease.
The Centers for Disease Control and Prevention (CDC) is investigating an unusual illness in a man to determine whether it was related to measles vaccination.
In January, March and August 1992, a 21-year-old man with hemophilia A and HIV infection had CD4 T-lymphocyte counts "too few to enumerate," said Will Schluter, MD, of the CDC. He spoke at a recent meeting of the Advisory Committee on Immunization Practices (ACIP). The man had not experienced an opportunistic infection.
In September 1992, the man received a second dose of measles-mumps-rubella (MMR) vaccine as a requirement for college entry. The following July, he began experiencing night sweats, chills and a nonproductive cough. He was hospitalized in August with a diagnosis of pneumonia. An open lung biopsy performed in October 1993 found measles virus, and measles pneumonitis was diagnosed, Schluter said. The man died in December 1993; the suspected cause of death was listed as cytomegalovirus encephalitis.
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The CDC is performing genetic sequencing on the virus to determine whether it is the vaccine strain. Preliminary data suggest that the isolate is the vaccine strain of measles virus; however, the lineage of wild measles is similar to that of the vaccine strain (Edmonston).
The package insert for MMR vaccine states that no live vaccine, including MMR, should be given to any severely immunocompromised individual, said David Nalin, MD, director for clinical research in infectious disease, Merck & Co., which manufactures MMR vaccine.
The question facing the ACIP and the American Academy of Pediatrics (AAP) Committee on Infectious Diseases (the Red Book Committee) is whether current measles vaccination recommendations for HIV-infected individuals should be changed based on a single unusual case report.
The AAP has not finalized its statement, said Neal Halsey, MD, chair of the Red Book Committee on Infectious Diseases and a liaison member of the ACIP. It is likely that the AAP will continue to recommend use of MMR with a caution for people who are "severely immunocompromised."
The ACIP agreed to continue recommending MMR vaccination for HIV-infected individuals who are asymptomatic. The vaccine may be withheld from individuals who have evidence of severe immunosuppression.
Canada, meanwhile, is enacting a second-dose measles vaccination policy and is in the midst of a massive catch-up campaign, said David Scheifele, MD, director, Vaccine Evaluation Center in Vancouver, British Columbia. Because of the case report, however, revaccination will be deferred for any child with severe immunosuppression, such as those on antiretroviral therapy.
Studies have shown that children infected with HIV are less likely to respond to measles immunization, but the response is more reliable when immunizations are given early in the course of HIV infection. But even a good response after early immunization does not necessarily protect an immunocompromised child, said Samuel L. Katz, MD, Wilbert C. Davison Professor, department of pediatrics, Duke University Medical Center, Durham, N.C.
"Even if you get an 80% to 90% seroconversion rate when you immunize early, these children lose antibody rapidly," Katz said. "You don't know how they will respond if they are challenged with natural infection two or three years later." Children exposed to measles virus should receive immune globulin regardless of vaccination history.
The key, however, is not necessarily vaccinating immunocompromised people, said W. Paul Glezen, MD, an ACIP liaison member from the Infectious Diseases Society of America.
"Protection of HIV-infected people depends on immunizing everyone around them," Glezen said. "We need to protect HIV-infected people from exposure to measles."
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