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Secondary measles vaccine failure in healthcare workers exposed to infected patients
L K Ammari1, L M Bell, R L Hodinka
1Department of Pediatrics, Children's Hospital of Philadelphia, PA 19104.
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.
Insights
Four vaccinated healthcare workers developed measles despite having pre-existing measles antibodies. This study highlights potential gaps in immunity detection and emphasizes the need for precautions in healthcare settings.
Area of Science:
- Infectious Diseases
- Immunology
- Public Health
Background:
- Measles remains a concern in healthcare settings, even with vaccination programs.
- Assessing protective immunity through antibody levels can be complex.
- Healthcare workers (HCWs) are at risk of exposure and transmission.
Purpose of the Study:
- To describe cases of measles in HCWs with pre-existing measles antibodies.
- To evaluate the effectiveness of current immunity assessment methods in HCWs.
- To inform infection control practices for measles in hospitals.
Main Methods:
- Screening of hospital employees for measles antibody levels using enzyme immunoassay (EIA).
- Review of clinical course and laboratory data for HCWs who developed measles.
- Inclusion of HCWs from various patient care roles at an academic tertiary care children's hospital.
Main Results:
- Four vaccinated HCWs developed measles despite positive pre-illness measles antibody levels.
- All affected HCWs showed a significant rise in measles-specific IgG post-infection.
- Three of the four HCWs had received at least two measles vaccinations.
Conclusions:
- Existing measles antibody levels may not always indicate adequate protective immunity in HCWs.
- Respiratory precautions are recommended for all HCWs caring for measles patients.
- Further research is needed to refine methods for assessing protective measles immunity in healthcare populations.
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