An ecological assessment of the impact of funded cocoon and maternal pertussis vaccination strategies on pertussis epidemiology in young infants - Australia, 2000–2017

  • Vaccine preventable diseases
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Background:
Despite the availability of pertussis-containing vaccines and high vaccination rates in children, pertussis (whooping cough) remains one of the most commonly notified vaccine-preventable diseases in Australia. ‘Cocooning’ (protecting infants by vaccinating close contacts), and maternal vaccination during pregnancy, are two pertussis vaccination strategies funded in various Australian states and territories to protect infants. The purpose of this study was to provide an ecological assessment of the impact of funded cocooning and funded maternal vaccination programs on pertussis epidemiology in young infants.

Methods:
We reviewed national pertussis notification data from 2000–2017, a period where there was high and stable coverage of primary course vaccination. Notifications in children aged <6 months were analyzed by relevant strategy time-periods for each Australian state and territory. The population-level impact of vaccination strategies on pertussis in young infants was assessed using a two-sample test of proportions to compare the proportion of notifications in children aged <8 weeks before and after periods of funded ‘cocoon’ and maternal vaccination strategies.

Results:
In Australia from 2000–2017 there were 5,904 pertussis notifications in children aged <6 months, with 1,903 (32.2%) occurring in children aged <8 weeks. During periods where maternal vaccinations strategies were funded, the proportion of notifications in children aged <8 weeks was 20.3%. This was significantly lower (p=0.002) than the proportion during periods where no such strategies were funded (27.9%). We were unable to identify any difference in proportions (p=0.670) when comparing periods before (34.8%) and after (34.2%) cocooning strategies were funded in various Australian states and territories.

Conclusion:
This study provides population-level support for the continuation of maternal vaccination during pregnancy as a strategy to protect children aged <8 weeks against pertussis infection in Australia.

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