Outbreak of measles in a hospital and measures taken against hospital infection--evidence of cost and benefits

Abstract

In Japan, an isolated vaccine of measles is used because MMR vaccines have been suspended due to the frequent occurrence of aseptic meningitis after their use. It is administered only once with the cover rate having been approximately 70%. An outbreak of measles was experienced in eight of our health care workers (three doctors, three nurses and two clerks of our hospital) and in seven of our medical students, accompanying local outbreaks. Their condition was severe enough to require admission to our school hospital. One of medical students developed encephalitis, but he has recovered completely. The social cost including medical cost per worker was approximately yen 500,000 (about $4,500). We measured antibodies against measles, rubella, chickenpox and mumps using the ELISA assay in 1048 health care workers less than 40 years of age and 99 medical students before their clinical practice two or three months after the outbreak. The cost including the measuring of antibodies and vaccination for these workers and students was approximately yen 2,800,000 and it will be yen 700,000 for new workers each year. The negative rates for workers were 1.2% for measles, 8.8% for rubella, 10.0% for mumps and 2.0% for chickenpox and those for the medical students were 1.0%, 22.0%, 9.0% and 5.0%, respectively. Of the workers, 9.6% who had more than the defined very high tiaer were thought to have subclinical reinfection because they were non-symptomatic. The rates were 1.2% for rubella, 0.5% for chickenpox and 0.0% for mumps for more than the defined high titers among the workers, suggesting a risk of outbreaks in the future. Therefore, the antibodies of health care workers and medical students should be measured at the hospital and the antibody-negative person should be vaccinated to prevent infection not only from their patients but also prevent other patients from becoming infected by contracted health care workers or students.