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; Rotarix® and RotaTeq®. Both vaccines were introduced into the Australian National Immunisation Program in July 2007. Each state and territory health agency independently selected a rotavirus vaccine to include in its immunisation schedule. Several Australian studies have shown that emergency room visits and hospitalisation for rotavirus have declined dramatically since vaccine introduction. The simultaneous introduction of two rotavirus vaccines in Australian states and territories has provided a unique opportunity to compare the impact of the different vaccines on the types of circulating rotavirus strains.
OBJECTIVE: This study details the rotavirus genotypes circulating in Australian children post vaccine introduction, and compares the genotype distribution between states using different rotavirus vaccines.
RESULTS: Prior to vaccine introduction our long‐term Australia‐wide surveillance program has shown that G1P[8] strains were the dominant type identified in 7 of 11 years. Since vaccine introduction, the dominant type has changed every year between 2007-12, with G1P[8], G2P[4] and G3P[8] representing the most dominant types between 2007 and 2012. G12P[8] strains emerged as an important genotype, being first identified in 2012, and have since become the most prevalent genotype during 2013 and 2015. This represents the first time this genotype has been a major cause of disease in Australia.
Australia is the only country where Rotarixä and RotaTeq® are used in specific regions. Each year differences in genotype distribution were noted based on vaccine type. For example, G2P[4] strains were more common in Rotarixä locations during 2007, 2008 and 2012, but more common in RotaTeq® locations during 2009 and 2010. The difference in genotype distribution between vaccines was further exemplified by the dominance of G12 in Australian states that use RotaTeq vaccine.
Full genome analysis of G1P[8] and G2P[4] strains suggests that strains from the vaccine era are genetically evolving, with unique changes observed in outer capsid proteins.
CONCLUSION: The Australian Rotavirus Surveillance program has shown that 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 between locations.