Introduction.

Rotavirus is the major cause of gastroenteritis in young children worldwide. In an effort to reduce the disease burden, two live oral rotavirus vaccines were developed. Both vaccines were introduced into the Australian National Immunisation Program in 2007. Multiple Australian studies have shown that hospitalisation for rotavirus has declined dramatically since vaccine introduction. The simultaneous introduction of two rotavirus vaccines in Australian states and territories provides a unique opportunity to compare the impact of the different vaccines on the rotavirus genotypes causing disease.

Objective

This study characterised the rotavirus genotypes circulating in Australia post vaccine introduction, and compared the distribution of genotypes between states using different vaccines.

Results.

Prior to vaccine introduction Australia-wide surveillance has shown that G1P[8] strains were the dominant type. Since vaccine introduction, the dominant type has changed yearly, with G1P[8], G2P[4] and G3P[8] representing the most dominant types between 2007-2012. G12P[8] strains have emerged as an important genotype, being first identified in 2011, and becoming a significant cause of disease during 2012, and the most prevalent genotype during 2013 and 2014. This represents the first time this genotype has been a major cause of disease in Australia.  

Australia is the only country where Rotarix and RotaTeq are used in specific regions. Each year differences in genotype distribution were noted based on vaccine type.

Full genome sequence analysis of strains from the vaccine era suggests that they are genetically evolving, with changes occurring in outer capsid proteins.

Conclusion

This study shows the distribution of rotavirus genotypes is more diverse and dynamic since the introduction of the rotavirus vaccine program into Australia. Both rotavirus vaccines exert selective pressure on circulating strains, and in any given year the prevalent genotypes differ. However, when the entire post vaccine period is combined the overall genotype distribution appears to be similar.