Antibody persistence and Haemophilus influenzae type b carriage after infant immunisation with PRP-T.
OBJECTIVE
To assess the persistence of serum Haemophilus influenzae type b antibodies and the prevalence of H influenzae type b carriage in a group of preschool age children previously vaccinated in infancy.


METHODS
Names were randomly selected from immunisation records. Families were visited on five occasions over a period of 12 months and throat swabs were taken from all family members present, with blood obtained from children at the first and last visits.


RESULTS
One hundred and fifty three children at a median age of 3.6 years had a geometric mean titre (GMT) of 1.06 micrograms/ml (95% CI 0.80 to 1.38). Eight per cent had an undetectable antibody concentration, received a booster dose of plain PRP vaccine, and responded with concentrations > 2 micrograms/ml. GMT at 4.5 years of age was 0.89 microgram/ml (0.69 to 1.16). Twelve children who had been exposed to H influenzae had a GMT of 4.7 v 0.8 micrograms/ml for those without exposure.


CONCLUSIONS
Accelerated immunisation against H influenzae without a second year booster results in persistence of satisfactory serum concentrations of antibody to 4.5 years of age. In those with undetectable antibody, immunological memory may still be present.
Heath
P T
PT
Department of Paediatrics, John Radcliffe Hospital, Oxford.
Bowen-Morris
J
J
Griffiths
D
D
Griffiths
H
H
Crook
D W
DW
Moxon
E R
ER
D000907:Antibodies, Bacterial / Q000097:blood*; D002353:Carrier State / Q000276:immunology / Q000382:microbiology*; D002675:Child, Preschool; D015721:Diphtheria-Tetanus-Pertussis Vaccine / Q000276:immunology; D018073:Haemophilus Vaccines / Q000276:immunology*; D019741:Haemophilus influenzae type b / Q000276:immunology*; D006801:Humans; D007117:Immunization, Secondary; D010614:Pharynx / Q000382:microbiology; D013745:Tetanus Toxoid / Q000276:immunology*; D018074:Vaccines, Conjugate / Q000276:immunology
D000907:Antibodies, Bacterial; D015721:Diphtheria-Tetanus-Pertussis Vaccine; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; D013745:Tetanus Toxoid; D018074:Vaccines, Conjugate