Immunogenicity of routine vaccination against diphtheria, tetanus, and Haemophilus influenzae type b in Asian infants born in the United Kingdom.

AIM

To determine the immunogenicity of routine vaccination against diphtheria, tetanus, and Haemophilus influenzae type b (Hib) in Asian infants born in the UK, and whether maternal antibody suppression occurs.

METHODS

A cohort study with 80% power, within 95% confidence limits, to show that 80% or fewer Asian infants would respond with an anti-PRP antibody concentration >0.15 microg/ml. Infants of South Asian origin born in Berkshire were enrolled at two general practices in Reading: 41 Asian families sequentially asked to participate within 2 weeks of birth; 36 infants were enrolled and 34 completed the study. Main outcome measures were: antibody concentration against diphtheria, tetanus, and Hib expressed as geometric mean titres (GMT) and proportion of infants about a threshold protective antibody concentration.

RESULTS

Median age for completing primary vaccination course was 5 months. All 34 achieved anti-PRP antibody concentration of >0.15 microg/ml, 33 were >1.0 microg/ml, and the GMT was 15.0 microg/ml. All infants developed protective antibody concentration >0.1 IU/ml for tetanus and diphtheria; the respective GMTs were 1.94 and 5.57 IU/ml. Infants with high (>0.25 IU/ml) antibody concentrations against diphtheria and tetanus at 2 months achieved lower antibody concentrations after their three dose course than those with low concentrations (<0.1 IU/ml) (p = 0.06 and 0.03, respectively).

CONCLUSIONS

Despite evidence for maternal antibody suppression of the response to tetanus and diphtheria vaccination, excellent antibody responses were achieved by routine vaccination according to the accelerated schedule. High vaccine coverage should be encouraged to provide protection against the possibility of imported infection.