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Modelling rubella in Europe
W J Edmunds1, O G van de Heijden, M Eerola
1Immunisation Division, PHLS Communicable Disease Surveillance Centre, London, United Kingdom.
Insights
Rubella vaccination programs aim to prevent congenital rubella syndrome (CRS). Mathematical modeling reveals that reducing vaccine uptake inequalities can yield greater health benefits than simply increasing coverage.
Area of Science:
- Epidemiology
- Virology
- Public Health
Background:
- Congenital rubella syndrome (CRS) is a significant complication of maternal rubella infection.
- Rubella vaccination programs aim to prevent CRS, but infant vaccination can alter infection age distribution.
- Certain vaccination strategies may inadvertently increase CRS incidence in non-immunized populations.
Purpose of the Study:
- To investigate the impact of various rubella vaccination policies in Europe using mathematical modeling.
- To analyze the transmission dynamics of rubella virus under different immunization scenarios.
- To assess the effectiveness of vaccination strategies in preventing rubella virus circulation and CRS.
Main Methods:
- Development and application of a mathematical model for rubella virus transmission dynamics.
- Simulation of pre- and post-vaccination patterns of infection and serological marker prevalence.
- Analytical and numerical analysis of model outputs under diverse scenarios.
Main Results:
- Endemic rubella circulation is unlikely in Finland, UK, Netherlands, and Denmark with uniform vaccine coverage.
- Insufficient infant vaccination coverage in Italy and Germany suggests probable continued CRS epidemics.
- Selective vaccination of schoolgirls with inadequate histories may suppress CRS incidence in some European countries.
Conclusions:
- Uniform and high infant rubella vaccine coverage is crucial for interrupting transmission.
- Reducing inequalities in vaccine uptake may offer greater public health benefits than increasing average coverage.
- Targeted strategies, like schoolgirl vaccination, can be important but may not replace robust infant immunization.
Abstract:
The prevention of congenital rubella syndrome (CRS), as a complication of rubella infection during pregnancy, is the main aim of rubella vaccination programmes. However, as vaccination of infants leads to an increase in the average age at which those who were not immunized become infected, certain rubella vaccination programmes can lead to an increase in the incidence of CRS. In this paper we use a mathematical model of the transmission dynamics of rubella virus to investigate the likely impact of different vaccination policies in Europe. The model was able to capture pre- and post-vaccination patterns of infection and prevalence of serological markers under a wide variety of scenarios, suggesting that the model structure and parameter estimates were appropriate. Analytical and numerical results suggest that endemic circulation of rubella is unlikely in Finland, the United Kingdom, The Netherlands, and perhaps Denmark, provided vaccine coverage is uniform across geographical and social groups. In Italy and Germany vaccine coverage in infancy has not been sufficient to interrupt rubella transmission, and continued epidemics of CRS seem probable. It seems unlikely that the immunization programmes in these countries are doing more harm than good, but this may be partly as a result of selective immunization of schoolgirls. Indeed, in both these countries, selective vaccination of schoolgirls with inadequate vaccination histories is likely to be an important mechanism by which CRS incidence is suppressed (unlike the other countries, which have had sufficiently high infant coverage rates to withdraw this option). Reducing inequalities in the uptake of rubella vaccine may bring greater health benefits than increasing the mean level of coverage.