Acellular pertussis vaccine use in risk groups (adolescents, pregnant women, newborns and health care workers): A review of evidences and recommendations

Pertussis is an acute infectious illness, caused by the bacteria Bordetella pertussis and commonly known as "whooping cough". Waning immunity after vaccination or after natural infection contributes significantly to the increasing incidence rates in adolescents and adults. Prevention of pertussis in industrialized countries is mainly based on immunization with acellular vaccines in combination with other antigens. A booster dose with an adult-formulation tetanus-diphtheria toxoid and acellular pertussis vaccine (Tdap) is now recommended for all adolescents by several countries, and replacement of the decennial Td dose with a single or more doses of Tdap is recommended for adults. Our review aims at describing the current knowledge on the impact of acellular pertussis vaccination in adolescents and adults, with particular focus on specific risk groups: adolescents, pregnant women and their newborns, and health care workers (HCWs), and secondly at suggesting possible immunization strategies. Data were retrieved by searches of Pubmed, references, from relevant articles and open-access websites. In countries where an adolescent booster dose was adopted, a certain decrease of incidence rates was observed. No serologic correlate of protection after immunization exists, but subjects with high antibody levels against pertussis antigens are less likely to develop the disease. Tdap vaccine was demonstrated to induce antibodies to pertussis antigens exceeding those associated with efficacy in infants, in both adolescents and adults. Tdap use in pregnant women seems to be safe and might represent a useful tool in order to prevent pertussis cases in the first months of life. Neonatal immunization with monovalent acellular pertussis vaccine can efficiently prime T and B cells and act as a basis for future immune responses. Cocooning strategies involving all those surrounding newborns have started to be implemented. Their impact on infant pertussis cases will be evaluated in the coming years. Coverage in HCWs should be increased, given their important role in pertussis transmission in health care settings. Despite the more recent position paper of WHO gives priority to infant and childhood vaccination against pertussis and leaves adolescent, adult and risk group immunization as an option for the future, data are quickly accumulating to support the need to consider pertussis vaccination as a crucial preventative intervention even in adolescents and special risk groups.