New Australian evidence suggests the protection offered by the monovalent rotavirus vaccine may wane over time and new strains are emerging.

A threefold increase in rotavirus notifications in 2017 prompted Australian epidemiologists to investigate the efficacy of the vaccine (Rotarix) and to characterise circulating strains.

In NSW alone, the outbreak resulted in more than 2000 notified cases and, nationwide, the number of cases more than doubled compared with 2016, their study has found.

It is the first investigation of Rotarix’s waning immunity beyond the third year of life, the authors say.