aP	acellular pertussis vaccine
CI	confidence interval
DTaP	diphtheria, tetanus and acellular pertussis vaccine (pediatric, full-dose toxoids)
DTP3	third dose of diphtheria–tetanus–pertussis-containing vaccine
DTwP	diphtheria, tetanus and whole-cell pertussis vaccine
ECDC	European Centre for Disease Prevention and Control
EU/EEA	European Union/European Economic Area
IgG	immunoglobulin G
IPV	inactivated poliovirus vaccine
PCR	polymerase chain reaction
Tdap	tetanus, reduced-antigen-content diphtheria and reduced-antigen-content acellular pertussis vaccine
Th	T helper
wP	whole-cell pertussis vaccine
WHO	World Health Organization