Modeling vaccination campaigns and the Fall/Winter 2009 activity of the new A(H1N1) influenza in the Northern Hemisphere

TL;DR

This study uses a global epidemic model to evaluate the effectiveness of vaccination campaigns against the 2009 H1N1 influenza, highlighting the importance of intervention timing and prioritization.

Contribution

It introduces a structured epidemic model to assess vaccination strategies for the 2009 H1N1 pandemic, emphasizing the role of timing and intervention prioritization.

Findings

Vaccination alone may not significantly reduce cases without delaying the peak.

Early vaccination is crucial but insufficient without additional interventions.

Prioritized vaccination can slow pandemic progression and lessen its impact.

Abstract

The unfolding of pandemic influenza A(H1N1) for Fall 2009 in the Northern Hemisphere is still uncertain. Plans for vaccination campaigns and vaccine trials are underway, with the first batches expected to be available early October. Several studies point to the possibility of an anticipated pandemic peak that could undermine the effectiveness of vaccination strategies. Here we use a structured global epidemic and mobility metapopulation model to assess the effectiveness of massive vaccination campaigns for the Fall/Winter 2009. Mitigation effects are explored depending on the interplay between the predicted pandemic evolution and the expected delivery of vaccines. The model is calibrated using recent estimates on the transmissibility of the new A(H1N1) influenza. Results show that if additional intervention strategies were not used to delay the time of pandemic peak, vaccination may not be able to considerably reduce the cumulative number of cases, even when the mass vaccination campaign is started as early as mid-October. Prioritized vaccination would be crucial in slowing down the pandemic evolution and reducing its burden.