ABSTRACT
Limited Early-Life Antibody Responses to Protein Antigens The magnitude of IgG antibody responses that may be elicited by protein antigens, whether in subunit or live attenuated vaccines, is also directly related to age at immunization (Table 1). The influence of immune immaturity on most currently available protein-based vaccines (such as combined diphtheria-tetanus-pertussis or hepatitis B vaccines) may not be assessed directly, as these vaccines do not induce significant antibody responses to a single vaccine dose even in adults. However, much higher antibody responses to the potent hepatitis A vaccine are elicited in toddlers than in infants of seronegative mothers (9), and the stepwise increase of antibody concentrations following measles (10-12) or mumps (13) immunization when immunization is delayed from 6 to 9, 12, or 15 months of age directly reflects the influence of age at immunization.
