670. Estimating Bordetella pertussis Seroprevalence in Persons Aged 10–25 Years in Mexico Using the 2012 National Health and Nutrition Survey (ENSANUT): Challenges and Lessons Learned

BACKGROUND: Low vaccination rates and under-detection of cases in adolescents and young adults have been implicated in the transmission of Pertussis to children. In this study, the proportion of adolescents and young adults with anti Bordetella pertussis IgG antibodies was estimated in a population-based survey in Mexico. METHODS: Frozen sera and data from 1,581 subjects—1,102 adolescents and 479 young adults (10–19 and 20–25 years old, respectively)—56% female were randomly selected from the Mexico’s National Health and Nutrition Survey (ENSANUT) 2012. CDC/FDA validated PT ELISA test was used to detect anti-pertussis toxin (PT) antibodies. A subset of 300 samples was also tested with Bp-IgG PT ELISA kit (Euroimmun AG, Lubeck, Germany(®)), both tests used international standards. Threshold values were established to identify vaccination or infection within the previous year, according to a US survey (Baughman et al.). Population-weighted estimates of seroprevalence were calculated. RESULTS: Overall Bp seroprevalence was 3.9% (95% CI: 2.3, 6.3); 3.1% (1.9, 5.0) in adolescents, and 4.9% (2.2, 11) in young adults. Seroprevalence did not significantly vary by gender, socioeconomic status, region or rural/urban location. Compared with the CDC/FDA PT ELISA, the Euroimmun(®) test showed 76% sensitivity, 88% specificity. CONCLUSION: Booster vaccination to Bp after toddlerhood is not in the Mexican national policy; therefore, anti-PT IgG seropositivity may reasonably be attributed to recent Bp infection. Our weighted estimates of recent Bp infection, which are based on a national population-based serosurvey and a standardized serological test, represent a considerable burden of infections in adolescents and young adults that sharply contrast with the official surveillance reports. Also, the Bp-IgG PT ELISA commercial kit lower sensitivity than the CDC/FDA PT ELISA may lead underestimation of recent infections. In conclusion, assessing pertussis seroprevalence requires careful consideration of the right tests and epidemiological model for interpretation. DISCLOSURES: All authors: No reported disclosures.