Abstract
Adult vaccination programs are receiving increasing attention however, little is known regarding the impact of age on the maintenance of the immune response. We investigated this issue in the context of a human papillomavirus (HPV) vaccination program collecting real-world data on the durability of humoral immunity in 315 female subjects stratified according to vaccination age (adolescents and adults) and sampled at early or late time points after the last vaccine dose. HPV-specific IgGs, but not memory B cells, were induced and maintained at higher levels in subjects vaccinated during adolescence. Nonetheless, antibody functions waned over time to a similar degree in adolescents and adults. To shed light on this phenomena, we analyzed quantitative and qualitative properties of lymphocytes. Similar biochemical features were observed between B-cell subsets from individuals belonging to the two age groups. Long term humoral responses toward vaccines administered at an earlier age were comparably maintained between adolescents and adults. The percentages of naïve B and CD4+ T cells were significantly higher in adolescents, and the latter directly correlated with IgG titers against 3 out of 4 HPV types. Our results indicate that age-specific HPV vaccine responsiveness is mostly due to quantitative differences of immune cell precursors rather than qualitative defects in B cells. In addition, our results indicate that adults also have a good humoral immunogenic profile, suggesting that their inclusion in catch-up programmes is desirable.
Highlights
Immunization programs for the pediatric population are usually well established, reaching coverage levels higher than those of adults[1]
Vaccination during adolescence induces high and long-lasting 4vHPV-specific IgG responses To determine whether the age of vaccination influences the induction and the duration of the immune response to the 4vHPV vaccine, human papillomavirus (HPV)-specific antibodies were measured 1–8 months (“Early cohort”) and 1–5 years (“Late cohort”) after immunization in female subjects stratified in two groups based on the age at the time of vaccination (Table 1): adolescents (10–14 y) and adults (18–53 y)
We evaluated the time-dependent decrease of 4vHPV-specific IgG in the two age groups measuring the correlation between antibody titers and time after vaccination
Summary
Immunization programs for the pediatric population are usually well established, reaching coverage levels higher than those of adults[1]. Adult immunization may pose some challenges from the immunological point of view[3,4] Questions such as what is the best age to be immunized, the frequency of booster doses and whether age influences the declining rate of immune responses, are well addressed for pediatric vaccines, while for adults they are mostly based on empirical observations[4,5]. In this context, it is crucial to fully understand the kinetics of vaccine immunogenicity and the duration of immune responses as a function of age of immunization, especially for those vaccines intended to protect the adult population. HPV vaccination represents an ideal scenario, being routinely administered to adolescents and in catch-up programmes for adults
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