Modeling the impact of rubella vaccination in Vietnam

Abstract

Supported by GAVI Alliance, measles-rubella vaccination was introduced in Vietnam in 2014, involving a mass campaign among 1-14 year olds and routine immunization of children aged 9 months. We explore the impact on the incidence of Congenital Rubella Syndrome (CRS) during 2013-2050 of this strategy and variants involving women aged 15-35 years. We use an age and sex-structured dynamic transmission model, set up using recently-collected seroprevalence data from Central Vietnam, and also consider different levels of transmission and contact patterns. If the serological profile resembles that in Central Vietnam, the planned vaccination strategy could potentially prevent 125,000 CRS cases by 2050 in Vietnam, despite outbreaks predicted in the meantime. Targeting the initial campaign at 15-35 year old women with or without children aged 9 months-14 years led to sustained reductions in incidence, unless levels of ongoing transmission were medium-high before vaccination started. Assumptions about contact greatly influenced predictions if the initial campaign just targeted 15-35 year old women and/or levels of ongoing transmission were medium-high. Given increased interest in rubella vaccination, resulting from GAVI Alliance funding, the findings are relevant for many countries.

Congenital rubella syndrome (CRS) in Vietnam 2011–2012—CRS epidemic after rubella epidemic in 2010–2011

“…From the surveillance data, hearing impairment was seen in only 9.6% of total confirmed CRS cases. Hearing impairment is one of the most common symptoms of CRS; however, in reports from the USA, Panama and Myanmar, hearing impairment among CRS infants were identified in 60%, 30% and 17%, respectively [7,12,13]. Hearing impairment is usually identified in the second year of life or later without standardized newborn hearing screening or hearing equipment available, so it is usually underreported in CRS surveillance.…”

“…Based on the results of this CRS surveillance and cost effectiveness analysis of RCV [13], the government of Vietnam is in the process of introducing RCV into Vietnamese national immunization programme. RCV is being introduced by an unprecedented catch-up campaign of Measles-Rubella combination vaccine targeting children aged from 9 months to 14 years in 2014-2015 by the support of Global Alliance of Vaccine Initiatives followed by introduction into the routine immunization programme.…”

The impact of Measles-Rubella vaccination on the morbidity and mortality from Congenital Rubella Syndrome in 92 countries

“…Country-specific numbers of CRS cases in year y during 2001-2080 were calculated by summing the number of CRS cases born each day to women aged 15-44 years (Supplementsection C). As assumed elsewhere, 1,9,13 infection during the first 16 weeks of pregnancy carries a 65% risk of the newborn having CRS ( Table 2). The number of CRS deaths in year y was calculated by multiplying the number of CRS cases born in year y by the assumed case fatality rate (30%see Table 2).…”

“…General structure and demography We used an age and sex-structured, deterministic, compartmental model of the transmission dynamics of rubella, following previous work. 1,13 The population is stratified into those with maternal immunity (lasting 6 months), susceptible, preinfectious (infected but not yet infectious), infectious and immune, using annual age bands and a "Realistic Age Structure. 14 Country-specific birth and age-specific death rates were fixed at 2010-15 levels and calculated from UN population survival data for 2010-15 respectively.…”

“…14 Country-specific birth and age-specific death rates were fixed at 2010-15 levels and calculated from UN population survival data for 2010-15 respectively. 12 The supplement to 13 provides the model's differential equations.…”