Economisation of vaccination against Haemophilus influenzae type b: A randomised trial of immunogenicity of fractional-dose and two-dose regimens

Rosanna Lagos*, Maria Teresa Valenzuela, Orin S. Levine, Genevieve A. Losonsky, Alvaro Erazo, Steven S. Wasserman, Myron Levine

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

52 Scopus citations

Abstract

Background. The cost of Haemophilus influenzae type b (Hib) conjugate vaccines has limited their use in non-industrialised countries. To identify more economical vaccination schedules, we carried out a randomised trial of the immunogenicity of alternative regimens to the standard three-dose series. Methods. 627 Chilean infants were randomly allocated to one of four regimens with either Hib polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) or Hib oligosaccharide-diphtheria mutant toxoid conjugate vaccine (PRP-CRM197), for a total of eight groups. All infants receive diphtheria-tetanus-pertussis (DTP) vaccine at ages 2, 4, and 6 months. The regimens included three full doses, three fractional doses consisting of one half or one third of the full dose, and a regimen of two full doses (at age 4 and 6 months). The primary outcome was the proportion of infants with serum anti-polyribosylribitol phosphate (PRP, the type b capsular polysaccharide) concentrations of 0.15 μg/mL or more at age 8 months. Findings. 93% (95% CI 85-98) of infants vaccinated with three full doses of PRP-T or PRP-CRM197 (95% CI 84-98) achieved anti-PRP concentrations of 0.15 μg/mL or more at age 8 months, compared with 91% (83-96) to 100% (95-100) of infants immunised with any fractional-dose regimen. Of the infants vaccinated with two doses of PRP-T or PRP-CRM197, 99% (93-100) and 87% (77-93) developed anti-PRP concentrations of 0.15 μg/mL or more, respectively. Interpretation. 91% (83-96) to 100% (95-100) of infants immunised with one-half or one-third of a full dose of Hib conjugate developed protective antibody concentrations. Carrier priming with DTP may make two-dose schedules an option in some places. These alternative regimens could bring the cost of Hib vaccines within reach of countries that currently cannot afford them.

Original languageEnglish
Pages (from-to)1472-1476
Number of pages5
JournalThe Lancet
Volume351
Issue number9114
DOIs
StatePublished - 16 May 1998

Bibliographical note

Funding Information:
The study was supported in part by a grant from the Children's Vaccine Initiative (CVI) based at WHO, Geneva, Switzerland. The measurement of PRP antibody was in part supported by Cooperative Research Agreement UO1-AI35948 with the National Institute of Allergy and Infectious Disease.

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