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EVIDENCE that infants can be protected against Haemophilus influenzae type b is accumulating, but the goal of extending that protection to those as young as 2 months of age has not yet been reached.
The evidence now is that the vaccine protects after the second dose, which is given at 6 months of age. So, if this schedule is followed, protection is expected by at least 7 months of age. (Although these vaccines have been available for several years, they heretofore have not been believed to be effective in children younger than 15 months.)
A considerable effort has been made to develop a vaccine that has efficacy in very young infants. One of the candidates is a conjugate vaccine developed by Praxis Biologics, Rochester, NY, in which an oligosaccharide obtained from the bacterial capsule is coupled to a single diphtheria protein derived from a nontoxic variant of diphtheria toxin.
Marwick C. Work Continues on Extending Protection Against Haemophilus influenzae to Very Young Infants. JAMA. 1990;264(2):164. doi:10.1001/jama.1990.03450020016002