Pertussis in young infants: a severe vaccine-preventable disease

of terms of the Creative Commons Attribution Non-Commercial License which permits unrestricted non-commercial use, distribution, and reproduction in any medium provided article is properly cited. a Sáfadi MAP. Pertussis in young infants: a severe vaccine-preventable disease [editorial]. Pertussis (also known as whooping cough) is a highly contagious disease mainly caused by the bacterium Bordetella pertussis. It is a strictly human disease and affects all ages. 1 However, the morbidity and mortality associated with pertussis are disproportionally high in young infants — the age group in which we observe virtually all hospitalizations, complications, and deaths related to pertussis. There is strong evidence in the literature showing that the severity of pertussis in these young infants is related to the production of toxins by B. pertussis, particularly pertussis toxin (PT). PT has a critical role in the pathogenesis of severe disease; it induces leukocytosis with lymphocytosis and elevated cAMP levels, which contribute to pulmonary vasoconstriction. Extreme leukocytosis is a marker of poor outcome in young infants with pertussis, and is frequently associated with severe hypoxemia, pulmonary hypertension, and death. The introduction of routine immunization programs against pertussis in children worldwide provided a substantial reduction in the incidence of the disease. However, control of the disease has never been achieved, and in the last decade a resurgence of pertussis was reported in several countries. Although the reasons for this resurgence are not fully understood, the probable factors that explain the observed increased rates of disease worldwide are: (i) the availability of more sensitive techniques (polymerase chain reaction) for the diagnosis; (ii) increased awareness and more efficient reporting among healthcare workers; (iii) genetic changes in B. pertussis strains; and (iv) rapid waning immunity after acellular vaccines. 9 The rapidly waning immunity, which occurs after either immunization or natural exposure to the causative agent, plays a critical role in disease transmission in the community. Several studies confirmed the importance of household contacts as the main source of pertussis transmission to unprotected young infants. The absence of the classic pertussis symptoms in most of the infected adolescents and adults makes the recognition of the disease and the diagnosis difficult in this age group. In order to anticipate protection against pertussis, the strategy of using pertussis vaccines during the newborn period has been attempted in several studies. Despite conflicting results, there was a trend toward lower responses to subsequent vaccine doses, either using whole-cell or acellular vaccines, …