Immunization Dialogue

Indian Pediatrics 2000;37: 209-210

Pertussis Immunization in Children with Neurological Illnesses

It is advisable to avoid pertussis vaccination when a neurological condition is evolving or is undiagnosed. Under the circumstances we may offer DT or acellular pertussis with DT (not available) to the patient. At a subsequent date, when the diagnosis of the neurological condition is clear and the situation is stable, if we desire to vaccinate against pertussis, do we have to give DPT as there is no monocomponent pertussis available? If we give this triple antigen, what is the impact on the immune system of such excess presentation of antigen? What should be the approach under the condition?

C.R. Sundaresan,
Consultant Child Specialist,
Kamineni Hospitals,
L.B. Nagar,
Hyderabad 500 068,


I agree with Dr. Sundaresan that on very rare occasions we may have to decide against giving DPT vaccine to an infant with an evolving or undiagnosed neurological illness. There are two reasons for this approach. First, we do not want do add a possible insult from the whole cell pertussis component, however remote that possibility is, to the brain that is already affected by some illness. Secondly, we do not want to confuse the diagnosis or evolution of that illness with an `adverse reaction to pertussis vaccine'.

There are 3 reasons why many people still consider the killed whole cell pertussis (wP) vaccine to cause such an adverse reaction. First, there is the temporal association of pertussis immunization and a variety of neurological illnesses in infants. Careful and extensive studies done in the UK and USA have shown that pertussis vaccine was not the cause of any such illness(1_3). Yet, we do know that some infants develop drowsiness (hypotonic, hyporesponsive) or inconsolable crying for unusually long periods after DwPT injections and we therefore suspect that the pertussis vaccine might possibly contain some factor that affects the brain. So we want to be extra cautious. Secondly, pertussis itself is well recognized to cause neurological complications including encephalopathy. So people assume that pertussis vaccine may also have such a potential, however infrequent that might be. In reality, pertussis encephalopathy is far more frequent than even any suspected pertussis vaccine adverse reaction of the CNS. Thirdly, pertussis vaccine is neurotoxic when injected intracerebrally in laboratory mice. This finding, although by itself trivial, adds an element of credence to the earlier two points.

Once we have decided against giving DwPT, we can still choose to give other vaccines. The immediate question is whether to give DT vaccine now or to wait until there emerges some clarity on the nature of the neurological illness. In a well immunized community, there is hardly any risk you take when the D toxoid antigen is postponed to a later and more judicious time. Tetanus is also not a problem in infancy (except for neonatal tetanus, the time of risk for which is long past when we are to consider DPT versus DT). In other words, there is no immediate hurry to give DwPT or DT while the neurological illness is being sorted out. We can easily wait several months or one year if needed, before we decide even to give DT instead of DwPT. If we were to give only DT, I would recommend two doses 3 months apart, and then to await the final decision on the nature of the neurological illness. If clearance is given for pertussis immunization, I would now recommend two doses of DwPT three months apart. Increasing the interval improves the immune response and we can safely wait another year or more until the time for the third dose, as the first booster with DwPT. In this manner, we have given only one extra dose of DT than the usual 3 plus one booster. Even if we give one or two or even three extra doses of D or T toxoid antigens, I do not think that there would be any adverse effect on the immune system. Both are very safe antigens.

When acellular pertussis (acP) vaccine or DacPT is available, then our choice would include an option either to give acP along with DT or DacPT instead of DwPT. Let me remined everyone that the time table to give DPT at 6, 10 and 14 weeks was necessary in the early phase of our national immunization program, but now in individual cases we have the option of delaying it a bit without putting the child at any risk, when the situation demands. In the usual course of events, there is no need to revise this timing (6, 10, 14 weeks) for general use, especially since everyone knows this schedule and a 6 week clinic visit is good for the baby and the mother. Rules are to give us guidance. Our primary responsibility is to individual children and we must take the child's best interests as the objective in all our decisions.

T. Jacob John,
2/91, Kamalakshipuram,
Vellore, Tamilnadu 632 002,


1. Miller DL, Ross EM, Alderslade R, Bellman MH, Rawson NSB. Pertussis immunization and serious acute neurological illness in children. Brit Med J 1981; 282: 1595-1599.

2. Shields WD, Nielson C. Relationship of pertussis immunization to the onset of neurological disorders: A retrospective epidemiological study. J Pediatr 1988; 81: 801-805.

3. Gale JL, Thapa PB, Wassilak SGF. Risk of acute serious neurological illness after immunization with diphtheria/tetanus/pertussis vaccine. JAMA 1994; 271: 37.


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