Australian Health Management Plan for Pandemic Influenza

3.4 How long would each phase last

While it is impossible to predict precisely how quickly a pandemic would evolve from one phase to another, estimates are provided in Table 3. The duration of later phases will be dependent on the availability of the vaccine, which will be rolled out progressively. Overall, it is anticipated that the pandemic in Australia could last for 7–10 months (from CONTAIN to the end of CONTROL). While interventions may extend the duration of a pandemic, they dramatically decrease the number of Australians affected at one time. The following provides a guide for planning purposes:

• The pandemic could move very quickly from ALERT to DELAY phase, or even move directly to the CONTAIN phase. Pandemic planning should ensure we can move quickly from preparedness activities to full response.
• If measures (detailed in Part 1, Section C2.1–2.2) such as assisting the overseas response and border measures, were implemented early in DELAY, the arrival of the pandemic virus into Australia could potentially be delayed for days to weeks. Timeframes for this delay would depend on the extent of the pandemic overseas and the volume of movement of people into Australia.
• Once the pandemic virus has arrived in Australia, it is believed that the infection could be contained if community control measures (Part 1, Section C2.3) are implemented early and appropriately. The CONTAIN phase could therefore last for a number of weeks or months, particularly if the pandemic virus is not highly infectious and the control measures are effective with high levels of compliance. Conversely, this phase could be relatively short if the pandemic virus is highly infectious and/or implementation of control measures is delayed or compliance is low.
• The move to the SUSTAIN phase will be when the number of new cases faced by jurisdictional health authorities exceeds the available resources for CONTAIN strategies. As it could take up to one year before sufficient vaccine would be available to bring the pandemic under control in Australia, it will be necessary to sustain essential services and continue to minimise transmission in SUSTAIN for several months.
• As it will take some time to vaccinate the population and for individuals to develop protective antibodies afterwards (Part 1, Section C2.4), the CONTROL phase could last for a number of weeks or months.
• The duration of the RECOVER phase is dependent on how long the health system takes to return to normal and whether there are subsequent waves. If second and additional waves of pandemic influenza do occur their severity will be dependent on how much protection the population has (from either natural infection and/or vaccination) and how much the virus has drifted.

Table 3: Possible duration of phases

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This information is current for 03 September, 2010
This information was issued on 05 December, 2008