Epidemiology of mumps outbreaks and the impact of an additional dose of MMR vaccine for outbreak control in regional Queensland, Australia, 2017-2018.

Background: In recent years, there have been ongoing outbreaks of mumps reported in Northern and North-Western Queensland, Western Australia and the Northern Territory, Australia. We aimed to define the epidemiology of mumps outbreaks in Central Queensland, Australia between October 2017 and October 2018 and evaluate the effectiveness of an additional dose of measles, mumps, rubella (MMR) vaccine.
Methods: A retrospective case control study was conducted, including outbreak investigations with laboratory-confirmed cases of mumps and subsequent comparison with matched controls. We analysed mandatory notifications from the Queensland Health Notifiable Conditions System database and immunisation information from the Queensland Health Vaccination Information and Admin System (VIVAS) and the Australian Immunisation Register.
Results: Between October 2017 and October 2018, there were 93 cases of mumps reported in Central Queensland with three distinct outbreaks: a discrete Indigenous community; a correctional facility; and a boarding school. Among all cases, 74 (79.6%) were fully vaccinated and 14 (15.1%) were partially vaccinated with MMR vaccine. Eighty-six cases (92.5%) were reported among Aboriginal and Torres Strait Islander people. In all outbreaks, an additional dose of MMR vaccine was offered with 35.4%, 73.6% and 35.8% of the target population being immunised in the discrete Indigenous community, the correctional facility and the boarding school, respectively. Prior to this additional dose of MMR, the mumps attack rate was 31.0 (95% confidence interval [95% CI]: 24.2-39.0) per 1000 population, compared to the post-additional dose MMR attack rate of 10.6 (95% CI: 6.7-15.9) per 1000 population.
Conclusion: An additional or booster dose of MMR should be included as an effective public health intervention strategy, particularly in communal or high-density living conditions to control mumps outbreaks in highly vaccinated populations.
(© Commonwealth of Australia CC BY-NC-ND.)