The effect of different rates of HbF:HbA production. Three distinct sets of parameters were used: τCf =50 and τCa =75; τCf =100 and τCa =150; or τCf =200 and τCa =300. As expected, when τCf and τCa are larger (i.e. there is more HbF for longer), the host is protected for a longer period of time. The solid lines are repeated from Figure 2 for comparison.