268071 Seroprotection against Measles Among British Columbia Women of Childbearing Age

Monday, October 29, 2012 : 11:35 AM - 11:50 AM

Monika Naus, MD MHSc FRCPC FACPM , Immunization Programs and Vaccine Preventable Diseases Service, BC Centre for Disease Control, Vancouver, BC, Canada
Vanita Sahni, MHSc , Immunization Programs and Vaccine Preventable Diseases Service, BC Centre for Disease Control, Vancouver, BC, Canada
Martin Petric, PhD , Laboratory Services, BC Centre for Disease Control, Vancouver, BC, Canada
Annie Mak , Public Health Laboratory Services, Provincial Health Services Authority, Vancouver, BC, Canada
Mel Krajden, BSc, MD (McG), FRCPC , Department of Pathology, BC Centre for Disease Control and University of British Columbia, Vancouver, BC, Canada
Background: An outbreak of measles occurred in British Columbia in the spring of 2010. Unimmunized children and under-immunized adults of childbearing age were the two prominent groups affected. Population-based seroprotection in adults was examined using banked prenatal specimens. Purpose: To assess seroprotection to measles among women of childbearing age in British Columbia to help guide immunization policy. Methods: Banked prenatal sera submitted for routine testing to the Provincial Health Services Authority Laboratory from January 2009 through December 2010 for years of birth from 1960 to 1979 were chronologically selected for testing. Specimens were tested for anti-measles IgG by the Behring assay. A required sample size of 662 samples in each of two birth cohorts was estimated based on assumed measles seropositivity of 95% in the 1960-1969 cohort and 92% in the 1970-1979, 5% type I error, and 60% power. Results: 1326 samples were included in the analysis. Ninety-two percent (1219/1326) of samples demonstrated immunity to measles. Ninety-five percent (95%CI 94,97) of women with years of birth 1960-9 had seroprotective levels, whereas 88% (95%CI 86,91) of women born 1970-79 had seroprotective levels with a trend to decreasing immunity with younger age observed when plotted by 5-year age groups. Reduction in seroimmunity at younger ages was associated with a higher proportion of equivocal results. Conclusion: Measles is a highly transmissible viral infection and population protection required to maintain herd immunity is estimated at 95%. Immunity as assessed by anti-measles IgG in younger adults is below the levels required to interrupt transmission.

Learning Areas:
Basic medical science applied in public health
Protection of the public in relation to communicable diseases including prevention or control
Public health biology
Public health or related public policy

Learning Objectives:
Describe trends in adults seroprotection against measles. Explain the role of serosurveys in assessing population based risk. Explain laboratory test methods used to assess immunity to vaccine preventable diseases.

Keywords: Communicable Disease, Immunizations

Presenting author's disclosure statement:

Qualified on the content I am responsible for because: I have had a career focus for 23 years in communicable disease control at the provincial level in Ontario and British Columbia with a focus in vaccine preventable diseases, including membership on the National Advisory Committee on Immunization for 12 years.
Any relevant financial relationships? No

I agree to comply with the American Public Health Association Conflict of Interest and Commercial Support Guidelines, and to disclose to the participants any off-label or experimental uses of a commercial product or service discussed in my presentation.