Immunity to polio, measles and rubella in women of child-bearing age and estimated congenital rubella syndrome incidence, Cambodia, 2012

Abstract

Significant gaps in immunity to polio, measles, and rubella may exist in adults in Cambodia and threaten vaccine-preventable disease (VPD) elimination and control goals, despite high childhood vaccination coverage. We conducted a nationwide serological survey during November-December 2012 of 2154 women aged 15-39 years to assess immunity to polio, measles, and rubella and to estimate congenital rubella syndrome (CRS) incidence. Measles and rubella antibodies were detected by IgG ELISA and polio antibodies by microneutralization testing. Age-structured catalytic models were fitted to rubella serological data to predict CRS cases. Overall, 29.8% of women lacked immunity to at least one poliovirus (PV); seroprevalence to PV1, PV2 and PV3 was 85.9%, 93.4% and 83.3%, respectively. Rubella and measles antibody seroprevalence was 73.3% and 95.9%, respectively. In the 15-19 years age group, 48.2% [95% confidence interval (CI) 42.4-54.1] were susceptible to either PV1 or PV3, and 40.3% (95% CI 33.0-47.5) to rubella virus. Based on rubella antibody seroprevalence, we estimate that >600 infants are born with CRS in Cambodia annually. Significant numbers of Cambodian women are still susceptible to polio and rubella, especially those aged 15-19 years, emphasizing the need to include adults in VPD surveillance and a potential role for vaccination strategies targeted at adults.

Tetanus Immunity among Women Aged 15 to 39 Years in Cambodia: a National Population-Based Serosurvey, 2012

“…The proportions of women with tetanus seroprotection and antibody levels of Ն1.0 IU/ml were lower among those aged 15 to 19 years (63 and 31%, respectively) and 20 to 24 years (87 and 60%) than among those aged Ն25 years (96 and 76%), similar to results for polio, measles, and rubella serosurveys in Cambodia (27). The discrepancy in seroprotection noted between parous (97%) and nulliparous (71%) women and the large proportion of parous women with antibody levels of Ն1.0 IU/ml (78%) suggest effective vaccination of most pregnant women through routine immunization (RI) services.…”

“…Increased susceptibility was not noted in the high/medium-risk areas from the 2009 risk assessment, indicating that the identified immunity gaps were closed by SIAs targeting high-and medium-risk areas (the majority of which were in the northern region) during 2009 to 2012 or that the risk assessment algorithm was insufficient in distinguishing high-risk areas. No regional differences in immunity were noted in the polio, measles, and rubella serosurveys in Cambodia (27). Determination of true population immunity by serosurvey is helpful in light of the challenges of collecting accurate vaccination histories (14,35).…”

“…During November and December 2012, we conducted a cross-sectional serosurvey among women aged 15 to 39 years in Cambodia. The two primary survey objectives were to estimate rubella and tetanus seroprevalence among WRA; polio, measles, and rubella serosurvey results are described elsewhere (27). The survey design and sample size were selected to provide national estimates by 5-year age strata.…”

“…Estimates of seroprotection and vaccination coverage with 95% (logit) confidence intervals (CIs) were calculated while accounting for the survey design by using STATA v13 (StataCorp, College Station, TX) (27). Anti-TT IgG concentrations generally correlate with the robustness and duration of seroprotection (28).…”

Estimating the burden of rubella virus infection and congenital rubella syndrome through a rubella immunity assessment among pregnant women in the Democratic Republic of the Congo: Potential impact on vaccination policy

“…Following previous methods, four age-structured catalytic models were fitted to the observed age-stratified 220 rubella antibody seroprevalence estimates from the different study sites using maximum likelihood to estimate 221 the force of rubella virus infection [23][24][25]. This was assumed to differ (models A and B) or be identical (models 222 C and D) for the ages <15 and ≥15 years [23,26].…”