Three and four dose schedules using a pentavalent combination vaccine
against diphtheria, tetanus, pertussis, polio and Haemophilus influenzae
maintain "satisfactory" antibody levels several years after dosing.
Researchers from Sahlgrenska University and other Swedish centres, with a
researcher from Aventis Pasteur MSD, Copenhagen, Denmark, studied a cohort
of children who received a pentavalent combination vaccine containing
diphtheria toxoid, tetanus toxoid, acellular pertussis, inactivated polio
and Haemophilus influenzae type b conjugate as infants.
Children received either two or three priming doses. All children also
received a booster dose after around a year. In the initial study, the
proportion of children who attained protective antibody concentrations did
not differ depending on the schedule. This paper reports follow-up after 4.5
years of 92 and 88 children that received a total of three and four doses
respectively.
In general, neither antibody concentrations nor the proportions of children
expressing protective levels differed significantly between groups. However,
a difference emerged in antibody concentrations to poliovirus type 3.
Seventy-six percent showed antibody levels of at least 0.01 IU/ml against
diphtheria by the Vero cell neutralization test, and 89 percent showed those
antibody levels by enzyme-linked immunosorbent assay. Ninety-three percent
showed levels of at least 0.01 IU/ml for tetanus and 97 percent expressed at
least 0.15 mu g/ml antibodies for Haemophilus influenzae type b.
Between 96 and 99 percent showed detectable antibody levels against
polioviruses type 3. The authors estimated the proportion of children with
detectable antibodies against pertussis toxoid as 44, 94 and 99 percent
depending on the method.
The authors concluded that levels of antibodies remained "satisfactory" 4.5
years following the initial dose. Moreover, no clinically relevant
differences in antibody concentrations emerged between the three and four
dose schedules.
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