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Do we need a booster of Hib vaccine after primary vaccination? A study on anti-Hib seroprevalence in Sweden 5 and 15 years after the introduction of universal Hib vaccination related to notifications of invasive disease
Authors: HALLANDER, HANS O.; LEPP, TIIA; LJUNGMAN, MARGARETHA; NETTERLID, EVA; ANDERSSON, MIKAEL
Source:Apmis, Volume 118, Number 11, November 2010, pp. 878-887(10)
Hallander HO, Lepp T, Ljungman M, Netterlid E, Andersson M. Do we need a booster of Hib vaccine after primary vaccination? A study on anti-Hib seroprevalence in Sweden 5 and 15 years after the introduction of universal Hib vaccination related to notifications of invasive disease. APMIS 2010; 118: 878–87. The prevalence of IgG ELISA antibodies against Haemophilus influenzae polyribosyl ribitol phosphate (anti-Hib) was studied in two Swedish seroepidemiologic materials. One study was performed in 1997 5 years after the introduction of universal Hib vaccination (N = 3320). Ten years later, a similar study was carried out to analyze the effect of vaccination on anti-Hib prevalence (N = 2383). The median values of anti-Hib concentrations (EU/mL) were almost identical in the two materials. The antigenic pressure including vaccination, natural infections and possible cross-immunizations was thus assumed to be constant. The joint median was 0.50 EU/mL (95% confidence interval: 0.46, 0.56). However, there were also indications of reduced exposure to ‘Hib-antigens’ over a 10-year period. The proportion above the cut-off point for protection, 0.15 EU/mL, decreased significantly for children aged 2–19 years from 78% in 1997 to 74% in 2007 (p = 0.034), and there was a significant increase in values below the minimal level of detection for adults from 17% in 1997 to 20% in 2007 (p = 0.009). In the 2007 material no specific age group could be identified with a lower immune profile than other age groups older than 3 years and there was a significant downward trend of invasive infections caused by Hib according to notification data for the period 1997–2008. Therefore, the conclusion is that presently there is no need for a booster dose of Hib vaccine in Sweden after primary vaccination but the situation should be carefully monitored.