Pertussis (whooping cough) is a bacterial infection of the respiratory tract resulting in severe coughing spells (paroxysms), often followed by an inspiratory whoop and vomiting. The paroxysmal stage lasts 2-4 weeks. The total duration of illness in uncomplicated cases is 6-10 weeks. Complications include apneic spells, seizures, pneumonia, encephalopathy, and death. Complications are much more common in the first year of life; the frequencies of pneumonia, seizures, and encephalopathy in young infants hospitalized with pertussis are 20%, 2.5%, and 0.5% respectively. At least half of those who develop pertussis encephalopathy sustain permanent brain damage.
Pertussis is prevented in over 80% of children who have received at least 3 doses of vaccine and is milder in vaccinated children who do become ill.
- ADVERSE REACTIONS
Common minor reactions to pertussis vaccine include:
fever 30oC 47% local redness 2.4 cm 7% swelling 2.4 cm 9% pain at injection site 51% drowsiness 32% fretfulness 53% anorexia 21% vomiting 6%
The incidence and height of fever can be significantly reduced by administration of acetaminophen (15 mg/kg/dose) at the time of vaccination and every 4 hours thereafter as necessary. Fussiness is also significantly reduced. Such treatment has less effect on local reactions.
Sterile abscesses may occur at a rate of 1 per 1000,000 doses, most often as the result of inadvertent subcutaneous injection of adsorbed vaccine.
- MATERIAL RISKS
Uncommon, but severe reactions occurring within 48 - 72 hours of vaccination include:
persistent, inconsolable crying 3 hr. - 1% convulsions - 1 in 1750 doses hypotonic-hyporesponsive state - 1 in 1750 cases encephalopathy - 1 in 140,000 doses permanent brain damage - 1 in 310,000 doses
The risk of encephalopathy and brain damage temporally associated with pertussis vaccine is under on-going study and is probably significantly less than the above figures, which are based on the U.K. Childhood Encephalopathy Study. On-going surveillance of adverse reactions to DPT in Alberta has resulted in an estimate of the same order of magnitude as the British study.
Administration of pertussis vaccine has not been shown to result in an increased risk of sudden infant death syndrome, infantile spasms, or Reye's syndrome.
There may be an increased risk of convulsions in a child with a history of previous seizure or with a history of seizures in parents or siblings. Such convulsions almost always occur in association with high fever and do not increase the risk of brain damage or subsequent epilepsy. The incidence of such seizures associated with fever can probably be reduced by the use of prophylactic acetaminophen as discussed above.
- REPORTABLE EVENTS
Major reactions occurring within 72 hours of vaccination, including: convulsion, hypotonic-hyporesponsive state, fever greater than 40.5oC, persistent crying over 3 hours, encephalopathy, and/or systemic allergic reaction.
THE NATIONAL ADVISORY COMMITTEE ON IMMUNIZATION (NACI) HAS MADE NEW RECOMMENDATIONS REGARDING PERTUSSIS IMMUNIZATION. "CONTRAINDICATIONS AND INDICATIONS" HAVE BEEN DIVIDED INTO "ABSOLUTE", "RELATIVE" AND "DEFERRED". PLEASE SEE CANADA COMMUNICABLE DISEASE REPORT 1993 (30 MARCH); 19-6: 41-44