Results of a sensitivity analysis in which the immunity loss rate is varied such that the expected duration of naturally acquired Influenza A(H1N1) immunity lasts 4 to 12 years. For each value, 1,000 simulations with about 80,000 individuals are run for 20 years; 2,000 simulations for the baseline duration of 6 years. The same rate is applied to all influenza infections leading to the same average duration for B/Vic and B/Yam, but to a shorter duration for A(H3N2), due to the more frequent appearance of drift variants (see Appendix 4 for details). Average annual number of infections for (a) the TIV scenario and (b) the QIV scenario. (c) Average number of infections prevented per year by QIV. Mean values are connected.