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

Paolo Bajardi1,2,9, Chiara Poletto1,9, Duygu Balcan3,4, Hao Hu4,5, Bruno Gonçalves3,4, José J. Ramasco1,9, Daniela Paolotti1,9, Nicola Perra3,6,7, Michele Tizzoni1,8,9, Wouter Van der Broeck1,9, Vittoria Colizza1,9 and Alessandro Vespignani1,3,4,9
1Computational Epidemiology Laboratory, ISI Foundation, Turin I-10133, Italy.
2Centre de Physique Théorique, Université d'Aix-Marseille, Marseille, France.
3Center for Complex Networks and Systems Research, School of Informatics and Computing, Indiana University, Bloomington IN, USA.
4Pervasive Technology Institute, Indiana University, Bloomington IN, USA.
5Department of Physics, Indiana University, Bloomington IN, USA.
6Linkalab, Cagliari, Italy.
7Department of Physics, University of Cagliari, Italy.
8Scuola di Dottorato, Politecnico di Torin, Turin, Italy.
9Complex Networks Lagrange Laboratory, ISI Foundation, Turin I-10133, Italy.

(November 2009)

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.