Friday, October 07, 2005

Key assumptions in US pandemic planning

The US has still not finalized its Pandemic Influenza Plan (now more than a month overdue from its original ridiculously tardy due date of August 2005), but a kind reader sent a powerpoint presentation from the Joint ACIP/NVAC [Advisory Committee on Immunization Practices/National Vaccine Advisory Committee] Meeting on Pandemic Influenza Vaccine Prioritization and Antiviral Medical Prioritization held at the Marriott Century Center Hotel in Atlanta, June 15 - 16 of 2005 (this summer) giving the key working assumptions. If you want to see the whole thing for yourself, here's the link (.ppt). For those who don't want the gory details, here is a quick summary (it is not easy to follow; presumably there was oral clarification and elaboration at the meeting):

Health impact:
  • 25 - 30% illness (20% - 30% in working age group), plus additional absenteeism for care-giving

  • Outbreak period in a community of 6 to 8 weeks per wave, with possibly more than one wave in a community

  • Length of illlness of an uncomplicated case, 5 days

  • Hospitalization rate of 1 - 10% of those who are ill

  • Mortality rate of .1 - 1%
  • Time from candidate vaccine strain to first dose probably 6 months or more

  • Current US production capacity, 5 million doses/week

  • Two doses/person necessary

  • Department of Defense likely a high priority for vaccination (.5 million to 1.5 million persons)
It is hard to judge the validity of the assumptions since there is little data to go on, but the mortality estimates seem low. The 1918 flu had mortalities of 2% - 3%, so the upper bounds of this estimate is only half or less of that episode. Some of the other estimates also seem low, but in truth no one knows what will happen.

And this scenario is bad enough.