Vaccination can place selective pressures on viral populations, leading to changes in the distribution of strains as viruses evolve to escape immunity from the
vaccine.
Vaccine-driven strain replacement is a major concern after nationwide
rotavirus vaccine introductions. However, the distribution of the predominant rotavirus genotypes varies from year to year in the absence of vaccination, making it difficult to determine what changes can be attributed to the
vaccines. To gain insight in the underlying dynamics driving changes in the rotavirus population, we fitted a hierarchy of mathematical models to national and local genotype-specific hospitalization data from Belgium, where large-scale vaccination was introduced in 2006. We estimated that natural- and
vaccine-derived immunity was strongest against completely homotypic strains and weakest against fully heterotypic strains, with an intermediate immunity amongst partially heterotypic strains. The predominance of G2P[4]
infections in Belgium after
vaccine introduction can be explained by a combination of natural genotype fluctuations and weaker natural and
vaccine-induced immunity against
infection with strains heterotypic to the
vaccine, in the absence of significant variation in strain-specific
vaccine effectiveness against disease. However, the incidence of rotavirus
gastroenteritis is predicted to remain low despite
vaccine-driven changes in the distribution of genotypes.