25 May 2007
WHO Updated Protocol for Rapid Operations to Contain Initial Emergence of Pandemic Flu Includes 20 Days (not 10) of Antiviral Prophylaxis
The World Health Organization (WHO) this month updated their interim protocol on “rapid operations to contain the initial emergence of pandemic influenza”. It contains several significant changes from the last major update in May 2006. The 22-page document is posted on the WHO avian influenza website at: www.who.int/csr/disease/avian_influenza/guidelines/draftprotocol/en/index.html
This conceptually and operationally valuable document includes sections on: ‘The decision to launch a containment operation; The containment strategy; Activities in the Containment Zone; Activities in the Buffer Zone; and Duration of the Containment Operation’.
Of the multiple pragmatic issues discussed in each of these sections of the document is the statement that “All persons in the Containment Zone considered unlikely to be infected would be given 20 days of antiviral prophylaxis. Although a 10-day course is the usual period for prophylaxis of seasonal influenza, extending prophylaxis for 20 days would allow for:
---Simpler logistical considerations: since it may take several days to distribute antivirals throughout the Containment Zone, extending the period of prophylaxis will increase the duration of time during which most or all of the population in the Containment Zone is on prophylaxis or treatment at the same time.
---Uncertainty about the characteristics for the emerging virus: the virus may have a longer incubation period than seasonal strains of influenza.
---Packaging considerations: oseltamivir is packaged in blister packs of 10 tablets.”
While this rationale is clear for 20 days of prophylaxis, i.e. 20 tablets of oseltamivir IF that is the drug used, this policy would mean that the current WHO antiviral stockpile of “3 million treatment doses (i.e. 2 doses per day for 5 days” (stated on page 12 of this WHO document) would be reduced if 20 tablets were used by each person for prophylaxis rather than 10 tablets (i.e. one tablet per day for 10 days.
Vigilance for actual influenza disease in persons initially given once-daily prophylactic doses, which would require changing to twice daily doses of oseltamivir as therapy, would be critical. In addition, .monitoring for oseltamivir resistance, as much as possible in real time, would also be important. “Such antiviral resistance would be more likely to develop in persons on once-daily prophylactic doses who are actually infected with the new pandemic flu virus and thus would require twice-daily dosing for a minimum of five days and possibly several more days. Further aspects of this new WHO interim protocol will be discussed subsequently.
Daniel R. Lucey, MD, MPH
Director, Center for Biologic Counterterrorism and Emerging Diseases, EROne Institutes, Department of Emergency Medicine, Washington Hospital Center
Adjunct Professor of Microbiology and Immunology
Website for this posting: www.BePast.org