Sensitivity of cumulative attack rates to epidemiological parameters. Cumulative attack rates were determined for a range of values of R
0 (1.2-1.8), latent period (2-4 days), and infectious period (5-7 days) in the presence of pH1N1 vaccination. The range of results observed for varying latent and infectious period lengths are presented for each value of R
0. Vaccination began the week of October 26, 2009 and continued for 8 weeks, to obtain the actual coverage levels outlined in Table 2. For a given value of R
0, the most steep curves (and highest attack rates in the presence of vaccination) were observed with a latent period of 2 days and infectious period of 5 days, and the least steep curves (lowest attack rates with vaccination) were observed with a latent period of 4 days and infectious period of 7 days.