Measles Outbreak in a Heavily Vaccinated Community: How Wide Should The Net Be Cast?
Method: We describe the public health response to a measles outbreak in Orange County, CA from 1/30/14-3/30/14 involving community and healthcare-associated cases. Primary and secondary cases and their associated exposures and risk factors were identified, including history of vaccination. The effect of different strategies taken by public health and hospitals and resultant case capture was reviewed.
Result: Among 22 measles cases, 6 were primary and 16 were secondary. 2,401 community exposures were identified by public health; 1,967 (81%) were healthcare-associated. 5 secondary cases occurred in HCWs, of which 4 had direct contact with measles patients; 4 had documented serologic immunity or receipt of two doses of measles vaccine. 4 HCWs worked while ill, resulting in evaluation of 1,051 healthcare exposures, but no transmission. Overall, among 16 secondary cases, 14 had face to face contact with known cases and 8 were considered immune. As the outbreak progressed, public health response to health care exposures transitioned from phone surveys of all exposed patients to phone contact of high-risk patients and letter notification of those exposed. 819 phone call surveys of patients yielded one secondary case in a fully vaccinated individual exposed in the healthcare setting. Over 1,000 letters mailed to patients did not identify any secondary cases. Overall, 880 public health person-hours were expended.
Conclusion: The burden of work was concentrated on a large number of casual patient exposures which yielded one secondary case. On the other hand, high risk face-to-face encounters resulted in secondary cases regardless of prior vaccination or immune status. Transitioning public health and hospital efforts to focus only on high risk direct exposures or high risk individuals regardless of documented immunity would have markedly reduced person-hours expended and would not have negatively impacted prevention measures or case finding.
S. K. Gohil,
S. Klish, None
S. S. Huang, Sage Products: Conducting a clinical trial for which contributed product is being provided to participating hospitals, Contributed Product
Molnlycke: Conducting a clinical trial for which contributed product is being provided to participating hospitals, Contributed product
M. Zahn, None