Sonam Wangchuk1, Francisco Nogareda2, Namgay Tshering3, Lekey Khandu4, Sonam Pelden5, Kathleen Wannemuehler6, Sonam Wangdi7, Ugyen Wangchuk8, Mick Mulders9, Tshewang Tamang10, Minal K Patel11. 1. Royal Centre for Disease Control, Ministry of Health, Royal Government of Bhutan, Wangchutaba, Serbithang, Thimphu, Bhutan. Electronic address: swangchuk@health.gov.bt. 2. World Health Organization Consultant, C/Juan de Austria, 13, 28010 Madrid, Spain. Electronic address: chesconogareda@hotmail.com. 3. Ministry of Health, Royal Government of Bhutan, P.O. Box: 726, Kawajangsa, Thimphu, Bhutan. Electronic address: ntshering@health.gov.bt. 4. Ministry of Health, Royal Government of Bhutan, P.O. Box: 726, Kawajangsa, Thimphu, Bhutan. Electronic address: lkhandu@health.gov.bt. 5. Royal Centre for Disease Control, Ministry of Health, Royal Government of Bhutan, Wangchutaba, Serbithang, Thimphu, Bhutan. Electronic address: spelden@health.gov.bt. 6. Global Immunization Division, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333, United States. Electronic address: kpw9@cdc.gov. 7. Ministry of Health, Royal Government of Bhutan, P.O. Box: 726, Kawajangsa, Thimphu, Bhutan. Electronic address: wangdis@who.int. 8. Ministry of Health, Royal Government of Bhutan, P.O. Box: 726, Kawajangsa, Thimphu, Bhutan. Electronic address: WANGCHUKU@who.int. 9. Expanded Programme on Immunization, World Health Organization, 20 Avenue Appia, 1211 Geneva, Switzerland. Electronic address: muldersm@who.int. 10. Ministry of Health, Royal Government of Bhutan, P.O. Box: 726, Kawajangsa, Thimphu, Bhutan. Electronic address: ttamang@health.gov.bt. 11. Expanded Programme on Immunization, World Health Organization, 20 Avenue Appia, 1211 Geneva, Switzerland. Electronic address: patelm@who.int.
Abstract
BACKGROUND: In 2017, measles elimination was verified in Bhutan, and the country appears to have sufficiently high vaccination coverage to achieve rubella elimination. However, a measles and rubella serosurvey was conducted to find if any hidden immunity gaps existed that could threaten Bhutan's elimination status. METHODS: A nationwide, three-stage, cluster seroprevalence survey was conducted among individuals aged 1-4, 5-17, and >20 years in 2017. Demographic information and children's vaccination history were collected, and a blood specimen was drawn. Serum was tested for measles and rubella immunoglobulin G (IgG). Frequencies, weighted proportions, and prevalence ratios for measles and rubella seropositivity were calculated by demographic and vaccination history, taking into account the study design. RESULTS: Of the 1325 individuals tested, 1045 (81%, 95% CI 78%-85%) were measles IgG seropositive, and 1290 (97%, 95% CI 95%-99%) were rubella IgG seropositive. Rubella IgG seropositivity was high in all three age strata, but only 47% of those aged 5-17 years were measles IgG seropositive. Additionally, only 41% of those aged 5-17 years who had documented receipt of two doses of measles- or measles-rubella-containing vaccine were seropositive for measles IgG, but almost all these children were rubella IgG seropositive. CONCLUSIONS: An unexpected measles immunity gap was identified among children 5-17 years of age. It is unclear why this immunity gap exists; however, it could have led to a large outbreak and threatened sustaining of measles elimination in Bhutan. Based on this finding, a mass vaccination campaign was conducted to close the immunity gap.
BACKGROUND: In 2017, measles elimination was verified in Bhutan, and the country appears to have sufficiently high vaccination coverage to achieve rubella elimination. However, a measles and rubella serosurvey was conducted to find if any hidden immunity gaps existed that could threaten Bhutan's elimination status. METHODS: A nationwide, three-stage, cluster seroprevalence survey was conducted among individuals aged 1-4, 5-17, and >20 years in 2017. Demographic information and children's vaccination history were collected, and a blood specimen was drawn. Serum was tested for measles and rubella immunoglobulin G (IgG). Frequencies, weighted proportions, and prevalence ratios for measles and rubella seropositivity were calculated by demographic and vaccination history, taking into account the study design. RESULTS: Of the 1325 individuals tested, 1045 (81%, 95% CI 78%-85%) were measles IgG seropositive, and 1290 (97%, 95% CI 95%-99%) were rubella IgG seropositive. Rubella IgG seropositivity was high in all three age strata, but only 47% of those aged 5-17 years were measles IgG seropositive. Additionally, only 41% of those aged 5-17 years who had documented receipt of two doses of measles- or measles-rubella-containing vaccine were seropositive for measles IgG, but almost all these children were rubella IgG seropositive. CONCLUSIONS: An unexpected measles immunity gap was identified among children 5-17 years of age. It is unclear why this immunity gap exists; however, it could have led to a large outbreak and threatened sustaining of measles elimination in Bhutan. Based on this finding, a mass vaccination campaign was conducted to close the immunity gap.
Authors: Hae Ji Kang; Young Woo Han; Su Jin Kim; You-Jin Kim; A-Reum Kim; Joo Ae Kim; Hee-Dong Jung; Hye Eun Eom; Ok Park; Sung Soon Kim Journal: Vaccine Date: 2017-06-29 Impact factor: 3.641