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Despite widespread vaccination against measles, some health care workers remain susceptible — and they have a much greater chance of contracting the disease than the general public, according to a recent report.
About 2% to 5% of U.S. health care workers may lack immunity, with greater susceptibility among younger workers, according to a review of research. Health care workers are two to 19 times more likely to acquire measles than other adults, the study found.1
As the Centers for Disease Control and Prevention celebrated the 50th anniversary of the measles vaccine — which led to the elimination of endemic measles in North America — public health experts urged continued vigilance. In 2013, there were 175 measles cases in the United States. The second-highest number since measles was eliminated in 2000. Twenty of those measles patients were hospitalized.
The largest outbreaks were in New York, North Carolina and Texas, and the U.S. cases came from 52 known importations of the disease, about half of them from Europe, the CDC said. Most of the U.S. cases occur among people who refused the vaccine for religious or philosophical reasons or infants too young to be vaccinated.
"Just as any virus anywhere is only a plane ride away, measles anywhere is really potentially the cause of an outbreak here," CDC director Thomas Frieden, MD, MPH, said at a press conference.
A systematic review of measles research revealed the need for continued concern about measles vaccination both in the United States and globally.
Even in the 1980s, measles outbreaks occurred in U.S. hospitals and emergency rooms and health care workers contracted measles from patients. From 1980 to 1984, about one-quarter of hospital-associated cases were among health care workers. Nosocomial transmission continues to occur in other countries, the reviewers found.
Although U.S. health care workers have very high rates of measles vaccination (90% to 98%), most states (80%) do not require it.
"Adult vaccines in general have not been funded from the public sector, so it's left up to the hospitals [to develop policies]," says Jane Seward, MBBS, MPH, deputy director of the Division of Viral Diseases in CDC's National Center for Immunization and Respiratory Diseases, an author of the review.
In European countries, vaccination practices differ widely, and the World Health Organization does not have a specific policy on measles vaccination or evidence of immunity among health care personnel. Vaccination rates are lower in European hospitals, Seward says.
In U.S. hospitals, concern arises when a measles outbreak occurs and the employee health professionals must quickly determine the immune status of health care workers.
Older health care workers may not have been vaccinated because CDC counts birth before 1957 as evidence of immunity — except in the case of an outbreak. CDC now says health care facilities "should consider" vaccinating health care workers born before 1957 if they don't have laboratory confirmation of immunity, past laboratory confirmation of disease or documentation of two doses of vaccine.2
"If even one case occurs in a health care setting, they're going to have to test them then," says Seward, "and that is very difficult when an outbreak goes on."
History of disease is no longer considered evidence of immunity, she notes.
CDC also says, "Health-care facilities should use secure, preferably computerized, systems to manage vaccination records for health-care personnel so records can be retrieved easily." Electronic records make it much easier to respond, says Seward. "Checking through hundreds of [paper] records when you have a case in the hospital is very time-consuming," she says.
If health care workers have received two doses of MMR, no serologic testing is necessary, she says. "Having two doses is highly effective," she says.