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.
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.
Swedish Institute for Infectious Disease Control, Solna, Sweden. hans.hallander@smi.se
Hans O
HO
Hallander
Tiia
T
Lepp
Margaretha
M
Ljungman
Eva
E
Netterlid
Mikael
M
Andersson
D000293:Adolescent; D000328:Adult; D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood; D016667:Bacterial Capsules / Q000008:administration & dosage / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D006192:Haemophilus Infections / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D018073:Haemophilus Vaccines / Q000008:administration & dosage / Q000276:immunology* / Q000592:standards; D006193:Haemophilus influenzae / Q000276:immunology*; D006801:Humans; D007114:Immunization / Q000379:methods*; D007117:Immunization, Secondary / Q000379:methods; D008875:Middle Aged; D016036:Seroepidemiologic Studies; D013548:Sweden / Q000453:epidemiology; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000276:immunology*; D055815:Young Adult
D000907:Antibodies, Bacterial; D018073:Haemophilus Vaccines; C044237:Haemophilus influenzae type b polysaccharide vaccine; D018074:Vaccines, Conjugate