We present two cases of bacterial meningitis caused by Haemophilus influenzae type b (Hib) which developed a few days after conjugate Hib vaccination.
[O]ver the past 20 years, there have been some reports of invasive Hib disease within a short period after administration of the vaccine [3–5]. This report describes two children in whom Hib meningitis developed a few days after vaccination. These cases serve as a reminder for clinicians of a phenomenon of elevated risk for infection and apparent vaccine failure in the short period after Hib immunization.
Case 1. A 10-week-old girl presented to another hospital with fever, refusal to eat, grunting respirations, and hyper- tonicity of 48-hour duration. All symptoms began one day after she had received the first dose of the combination Infanrix-IPV+Hib vaccine (a combined vaccine against diphtheria, tetanus, pertussis, polio, and Hib infections). Her parents reported that she had been perfectly healthy the day before vaccination.
At the present admission to the other hospital, bacterial meningitis was suspected… [T]reatment… was started. Two days later, both blood and CSF cultures grew Haemophilus influenzae, which was identified as type b…
The patient’s clinical status gradually improved over the next 4 days, when a secondary fever was noted in addition to new-onset seizures.
Case 2. A 5-month-old boy presented to our hospital with fever, apathy, vomiting, and diarrhea of 24-hour duration. All symptoms began 6 days after he received the second dose of the Infanrix-IPV+Hib vaccine. His parents reported that he had been perfectly healthy on the day before vaccination.
Past medical history was unremarkable. The patient was born after a normal term pregnancy and vaginal delivery. He received the first dose of Infanrix-IPV+Hib vaccine at age of 2 months without adverse events.
At admission, the patient was febrile and apathetic, with grunting respiration and a bulging fontanel. [T]reatment… was started. After 36 hours, blood culture grew Haemophilus influenzae, which was later identified as type b…
Booy et al. [3] investigated all cases of invasive Hib infection that occurred over a 3-year period in children in the United Kingdom after they received at least one dose of the Hib-conjugate vaccine. They identified two kinds of vaccine failures: apparent (early) and true (late). True failures were defined as Hib invasive disease occurring either >1 week after a child up to the age of 12 months received at least two doses of the vaccine, or >2 weeks after a single dose was received by a child >12 months of age. Hib invasive infections that occurred within one week after the administration of one or two doses of vaccine were considered apparent vaccine failures. Thus, in the present report, both cases represent apparent (early) vaccine failures.
In Booy’s work [3], they reported of 46 apparent vaccine failures [28%] out of the 164 cases of invasive disease among the entire population of United Kingdom vaccinated children.
This phenomenon of postimmunization provocative disease was also confirmed in early studies of conjugated and unconjugated Hib vaccines which reported that subjects with preexisting anticapsular antibodies showed a decrease in antibody concentrations after immunization.
The exact mechanism underlying the invasive infection in our patients could not be determined…
However, these cases are reported to serve as a reminder to clinicians of the risk, albeit rare, of invasive Hib disease in the short period after successful immunization. Clinicians should bear this possibility in mind when starting empiric antibiotic treatment in children who present with signs of infection within a week of receiving the vaccine. Large-scale studies that focus on this time frame are still needed.