Recent increases in mumps incidence in Australia: the "forgotten" age group in the 1998 Australian Measles Control Campaign.

OBJECTIVES

To describe the epidemiology of mumps and examine potential factors underlying the recent increase in the incidence of mumps in Australia.

DESIGN, SETTING AND

PARTICIPANTS

Analytical descriptive study, for all Australian states and territories, of mumps notifications (1994-2007); hospitalisations for mumps (1994-2005); and mumps seroprevalence in a nationally representative sample of 2787 subjects (1997).

MAIN OUTCOME MEASURES: Incidence of notifications and hospitalisations for mumps; seropositivity by birth cohort.

RESULTS

Notified mumps cases increased from 60 in 2002 to 231 in 2005 and 512 in 2007. Between 1994 and 2005, there were 605 hospitalisations for mumps. Mumps seropositivity in all states and territories in 1997 was high (range, 87.1%-94.3%). The predominant age group affected by mumps shifted to adults over time: between 2005 and 2007, 41% of cases occurred among people aged 20-29 years. Cases were concentrated among the birth cohort of 1978 to 1982, who had higher rates of notifications and hospitalisations for mumps and a lower seropositivity rate (92% [95% CI, 89%-94%]) than other birth cohorts.

CONCLUSIONS

The birth cohort of 1978 to 1982 was too old to reliably receive a second dose of measles-mumps-rubella (MMR) vaccine in the 1998 Australian Measles Control Campaign and too young to have had mumps infection. Renewed efforts to maximise two-dose MMR coverage are important for prevention of mumps and measles in young adults.