US Influenza Virus Seasonal Forecast


  • Ascel Bio is not anticipating a vaccine mismatch year at this point in time; however, we will need to re-assess in the coming weeks.
    • The few reports of flu activity so far this year in the US appears to be type A/H3N2. H3N2, when considered at baseline, is associated with a moderate probability for vaccine mismatch. Vaccine mismatch does not guarantee seasonal severity. And severity is not well defined – each age group experiences different severity levels for influenza.
    • The northern hemisphere vaccine for the 2015/16 season was updated for the southern hemisphere A/H3N2 strain that caused the trouble last year. Therefore, given the early indicators, Ascel Bio is not expecting a problem this season.
  • Ascel Bio did note an unusually early increased RSV Type A activity being reported, in late August, but there have since been no reports of unusual activity. In other words, this could have been an isolated report. Ascel Bio will be monitoring closely as unusual RSV behavior suggests potential to have a bad year for pediatric inpatient care and pediatric ICU bed status. This early indicator requires active monitoring for further validation. RSV is the #1 most disruptive infectious agent to the pediatric medical infrastructure in terms of potential to overwhelm urban PICU grids in developed countries.
  • We have received additional intelligence regarding unusual influenza activity in Australia due to type B (B/Brisbane), where they are seeing a type B-dominant season overall (i.e. type B has dominated over type A influenza). Type B influenza is a non-pandemic subtype of influenza typically associated with potential to disrupt outpatient sectors of the medical infrastructure (e.g. outpatient clinics, urgent cares, and ED overflows). We worry less about ICU grid strain with type B than with type A. What has happened is a “vaccine mismatch”, where the more broadly used trivalent formulation in Australia did not include B/Brisbane, but the newly available quadrivalent vaccine did. Approximately 25% of the Australian isolates are B/Brisbane, which they believe is the culprit in seeing high numbers of cases there. The current situation is a weak IDIS Category 3 event (crisis).
  • Bottom line for the US / Canada / UK is to demonstrate the following in the coming weeks:
    • Diagnostic proof that B/Brisbane has entered the northern hemisphere.
    • Evidence that the vaccine formation for type B influenza does not include B/Brisbane.
    • Diagnostic proof that B/Brisbane is outcompeting other B strains.
  • The fact that this is being observed in Australia is an “FYI” at this point and does not warrant any action other than to await further information as the season begins in the northern hemisphere. We often observe activity patterns in the southern hemisphere that do not necessarily imply anything for the northern hemisphere experience. Currently in the US, we are seeing scant reporting of A/H3N2 dominance, not type B dominance.

Watch Notice

All reporting signatures are within normal limits.
The 2014/15 influenza season was dominated by transmission of H3N2 strain of the virus. This strain did not match the vaccine strain and this mismatch led to the highest rate of infection in those >65 years in the past 10 years. This season, the vaccine has been updated, and at this time Ascel Bio is not anticipating an unusually severe influenza season.

Category: news

Posted on: Sep 28, 2015 | Share:
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