Pertussis in Individuals with Co-morbidities: A Systematic Review

Plain Language Summary Pertussis, or whooping cough as it is more commonly known, is a respiratory disease that mainly affects young children, although it can be caught at any age. An increasing number of cases are being identified in older adults. This is concerning since older people typically have other underlying health conditions that can increase the risk of severe outcomes leading to increased mortality. We assessed 34 published studies that examined the link between whooping cough and some health conditions. Several studies found that prior whooping cough was more likely in those with an underlying health condition, and this was particularly true in those with respiratory conditions like asthma and chronic obstructive pulmonary disease, whilst there were also studies which showed that having some health condition(s) might increase the risk of developing severe whooping cough which might require medical attention or hospitalisation. There was also some evidence that previous whooping cough might be protective against some blood cancers. Whooping cough was shown to exacerbate several underlying health conditions, although a single study found that it may reduce the risk of chronic bronchitis exacerbations. More research is required to corroborate these findings. Pertussis is a highly contagious disease of the respiratory tract caused by Bordetella pertussis. Although the burden of pertussis is highest in children, available data suggests that pertussis in the elderly and those with underlying chronic conditions or illnesses can result in significant morbidity, mortality and costs. We undertook a comprehensive review to assess the association between pertussis and chronic conditions/illnesses. A search was undertaken on 17 June 2019 across EMBASE, Medline and BIOSIS. Citations were limited to those in English, in humans and published since 1 January 1990. There were 1179 papers identified with an additional 70 identified through a review of the reference lists. Of these, 34 met the inclusion criteria. Papers included were categorised in groups, those which reported: associations between prior pertussis and subsequent chronic conditions or illnesses; a link between chronic conditions/illnesses and subsequent risk of pertussis; and those which reported on the effect of the chronic conditions/illnesses on pertussis complications or exacerbations. Pertussis appears to increase the likelihood of developing some chronic conditions/illnesses, but also appears to decrease the likelihood of developing some haematological cancers. There were several chronic conditions/illnesses where the study results were mixed, and several studies that found no association with previous pertussis. There were also studies which showed that having some comorbid health condition(s) might increase the risk of developing pertussis. Three studies showed pertussis can lead to increased exacerbations of chronic conditions/illnesses and associated hospitalisations, although one study showed it reduced the effects of chronic bronchitis. Previous pertussis appears to contribute to the increased likelihood of developing some respiratory conditions like asthma, and conversely those with asthma or COPD are at increased risk of severe pertussis requiring further intervention. Further research is required to confirm or disprove these associations, and to characterise the pathophysiological mechanisms behind the potential associations with pertussis.