Hey, thanks! Yeah, it seems to have been a bit of a global resurgence that year. The diseases has a natural 4 year cycle and in 2012 it looks like the move, around a decade previously, to the safer acellular vaccine offers a shorter period of protection. This means that the disease was actively circulating in adolescents and being passed on to younger infants in the family. This is what I’ve heard for colleagues that do the epi on this one.

Here’s the incidence of pertussis per 100 000 of the pop in the US up until 2011. The cycle is clearer in this. . Source