In both 1997 and 2007, the highest proportion of detectable anti-PT concentrations (≥1 EU/ml) was observed in the oldest age groups 17.7–18.7 years in 1997 and 17–18 years in 2007 (99% and 83%, respectively), although the proportion was significantly lower in 2007 (p < 0.001), a decade after the reintroduction of pertussis vaccination (Fig. 2A,B). The gene discussed is F2; the disease is pertussis.