FoggyRock General Forum

In implicating pertussis vaccination in the evolution of subsequent neurological residua, a careful consideration of the mechanism for vaccine-induced brain damage plays an important supporting role. Pertussis toxin has been shown to alter cellular signaling. It also affects the catecholaminergic and GABAergic systems in the brain. In addition, a direct, endotoxin-mediated attack on the endothelial cells could create a local defect of the blood-brain barrier. It is being seen that a combination of one or more bacterial toxins, asphyxia, Co2 retention and loss of cerebral autoregulation is responsible for neurological symptoms.

Encephalopathy manifests with alteration of sensorium or generalized or focal seizures that persist for more than a few hours. Occurrence of hypotensive-hyporesponsive shock or post-vaccination encephalopathy is a contra-indication of further doses of the pertussis component. This should be explained to the guardians. Other manifestations that indicate occurrence of encephalopathy include: seizures with or without fever occurring within 3 days of immunization and persistent, severe, inconsolable screaming or crying for 3 or more hours within 48 hours of immunization. Usually, these are not associated with permanent sequel. Previously, occurrence of these events also meant withdrawal of pertussis component from doses to be received in future. However, it is now recommended that all factors should be considered while advising regarding DPT vaccination in future in these children.

Association of severe reactions made the whole- cell pertussis vaccine highly unpopular among many communities and countries and spurred research for safer vaccines. Some European countries even went to the extent of withdrawing (whole-cell) pertussis vaccination; only to find an increased incidence of and increased morbidity due to pertussis amongst infants and young children in the community. An acellular pertussis vaccine (Designated as aP) is now available in several countries including India. It contains purified, inactivated components of B. pertussis. The acellular vaccine is as potent as the whole cell vaccine, but it is still associated with neurological complications described with whole-cell vaccine, albeit at a much lower frequency. It is also credited with lesser incidence of local side effects as well as decreased incidence of severe reactions like seizures and hypotensive episodes. However, the vaccine is expensive and it is unlikely that it would be included in the Indian National immunization schedule in near future.