One month post-primary vaccination, all subjects in both groups were seropositive for anti-pertussis toxin (PT), anti-filamentous haemagglutinin (FHA) and anti-pertactin (PRN) antibodies (≥5 EL.U/ml) and the vaccine response rates to the pertussis antigens were above 97% and 98% in the 6–10–14W and 2–4–6M groups, respectively, for at least one antigen (Table 2). Here, F2 is linked to pertussis.