Pt. Heath et al., Clinical and immunological risk factors associated with Haemophilus influenzae type b conjugate vaccine failure in childhood, CLIN INF D, 31(4), 2000, pp. 973-980
Haemophilus influenzae type b (Hib) conjugate vaccines have proved extremel
y efficacious in healthy children. True Hib vaccine failures are rare. Hib
conjugate vaccines were introduced for routine immunization in the United K
ingdom and the Republic of Ireland in 1992, Coincident with this, active pr
ospective and national surveillance via pediatricians, microbiologists, and
public health physicians was commenced to assess the clinical and immunolo
gical factors associated with vaccine failure. During the 6 years of the st
udy, 115 children with true vaccine failure were reported. Of the children
who were vaccinated before 12 months of age, a clinical risk factor was det
ected in 20%, an immunological deficiency was detected in 30%, and one or b
oth were detected in 44%. Children who were vaccinated after 12 months of a
ge were more likely to have one or both factors (67%). Thirty percent (33 o
f 105) of children with true vaccine failure had a low Hib antibody respons
e (concentration, <1.0 <mu>g/mL) after disease, but the majority then respo
nded to a further dose of Hib vaccine. Children who develop Hib disease des
pite vaccination deserve further clinical and immunological evaluation.