RESUMEN
Introduction: South Africa is yet to introduce rubella-containing vaccines (RCV) into its routine immunization schedule. Selecting the target population when introducing RCV should take into account the ages of susceptible individuals in the population. We aimed to determine the seroprevalence of antibodies to rubella and characterize immunity gaps among individuals of all ages in South Africa. Methods: We tested for rubella immunoglobulin G (IgG) antibodies with a commercial enzyme-linked immunosorbent assay. We used residual samples collected from 2016 through 2018 as part of the national measles surveillance program. We only tested samples that were negative for measles and rubella immunoglobulin M (IgM) and explored the association between rubella susceptibility (IgG negative) and predictor variables (year of sample collection, age, sex, and province of residence) using logistic regression analysis. Results: We obtained results for 6057 records. Rubella susceptibility was highest among Individuals aged zero to 11 months (81.9%), followed by children 1 to 5 years old (71.5%), 6 to 10 y old (40.9%) and 11 to 15 y old (31.25) while the smallest proportion of susceptible individuals was among those 16 to 49 y old (19.9%). Females were less likely to be susceptible to rubella compared to males (OR = 0.79 (95%CI: 0.71-0.87), P < .001) in unadjusted analysis but this effect was not observed after adjusting for age and province. In multivariable logistic regression, age (OR = 6.24 (4.52-8.63), P < .001) and province of residence (OR = 0.97 (95%CI: 0.95-0.99), P = .01) were associated with rubella susceptibility. Conclusion: In the absence of rubella vaccination in the Expanded Program on Immunization in South Africa, the bulk of individuals susceptible to rubella are children under 16 y old. About 20% of individuals 16 to 49 y old are susceptible to rubella. This susceptibility gap must be born in mind during RCV introduction.
Asunto(s)
Sarampión , Rubéola (Sarampión Alemán) , Anciano , Anticuerpos Antivirales , Niño , Preescolar , Estudios Transversales , Femenino , Humanos , Lactante , Masculino , Sarampión/epidemiología , Sarampión/prevención & control , Vacuna contra el Sarampión-Parotiditis-Rubéola , Rubéola (Sarampión Alemán)/epidemiología , Rubéola (Sarampión Alemán)/prevención & control , Virus de la Rubéola , Estudios Seroepidemiológicos , Sudáfrica/epidemiologíaRESUMEN
BACKGROUND:The World Health Organization; African Region; set the goal of achieving measles elimination by 2020. Namibia was one of seven African countries to implement an accelerated measles control strategy beginning in 1996. Following implementation of this strategy; measles incidence decreased; however; between 2009 and 2011 a major outbreak occurred in Namibia.METHODS:Measles vaccination coverage data were analysed and a descriptive epidemiological analysis of the measles outbreak was conducted using measles case-based surveillance and laboratory data.RESULTS:During 1989 - 2008; MCV1 (the first routine dose of measles vaccine) coverage increased from 56% to 73% and five supplementary immunisation activities were implemented. During the outbreak (August 2009 - February 2011); 4 605 suspected measles cases were reported; of these; 3 256 were confirmed by laboratory testing or epidemiological linkage. Opuwo; a largely rural district in north-western Namibia with nomadic populations; had the highest confirmed measles incidence (16 427 cases per million). Infants aged =11 months had the highest cumulative age-specific incidence (9 252 cases per million) and comprised 22% of all confirmed cases; however; cases occurred across a wide age range; including adults aged =30 years. Among confirmed cases; 85% were unvaccinated or had unknown vaccination history. The predominantly detected measles virus genotype was B3; circulating in concurrent outbreaks in southern Africa; and B2; previously detected in Angola.CONCLUSION:A large-scale measles outbreak with sustained transmission over 18 months occurred in Namibia; probably caused by importation. The wide age distribution of cases indicated measles-susceptible individuals accumulated over several decades prior to the start of the outbreak