Secondary Measles Vaccine Failure in Healthcare Workers Exposed to Infected Patients

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Abstract
Objective: To describe 4 healthcare workers who developed measles despite pre-existing antimeasles antibody levels. Design: Hospital employees working in patient care areas from July through November 1990 were screened for measles antibody levels using a commercially available enzyme immunoassay (EIA). The clinical course and laboratory evaluation of the 4 healthcare workers who developed measles were reviewed. Setting: An academic tertiary care children's hospital. Participants: A convenience sample of resident physicians, nurses, ward clerks, Child Life workers, physical and occupational therapists, radiology technicians, and housekeeping staff were screened regardless of age, immunization status, or history of measles infection. Results: Of 1,311 employees working in patient care areas, 900 (68.6%) had sera tested for measles antibody. Fourteen (1.5%) were negative, 338 (37.6%) had low positive antibody levels, 372 (41.3%) were mid-positive, and 171 (19%) were high-positive; 5 (0.6%) showed equivocal results. Four healthcare workers vaccinated in the past developed measles. All had positive pre-illness measles antibody levels and all had a significant rise in measles-specific IgG following infection. Three of the them had received at least 2 live measles vaccinations prior to caring for patients with measles. Conclusions: These cases raise concerns regarding detection of adequate protective measles immunity. We recommend that all healthcare workers observe respiratory precautions in caring for patients with measles.