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Immunization coverage for three doses of the diphtheria-tetanus-pertussis and poliomyelitis vaccines in infants is high worldwide, therefore despite the lack of documentation of past vaccinations, most migrant children do not require complete revaccination. Our strategy was to administer a single dose of a tetanus toxoid containing vaccine (TTCV) to migrant children followed by anti-tetanus toxoid (TT) serology to determine whether additional vaccine doses were required. Our goal was to estimate the basic TTCV coverage and to identify potential determinants of the vaccination response. Newly arrived migrant children were prospectively enrolled between October 2014 and August 2017. We included patients aged 1–18 years with no proof of past vaccinations who accepted a single dose of TTCV. Anti-TT serology was performed after 4–6 weeks, and an anti-TT level ≥ 1 IU/mL was considered a booster-type antibody response with no need for additional doses of TTCV. Potential determinants of the vaccination response were identified using univariate and multivariate linear regression analyses. Two hundred and eight children were eligible for analysis. The mean age of the children was 9 (±4.5) years and 100 (48%) were female. The majority (n = 129, 62%) of the children came from the WHO Eastern Mediterranean region. Only three patients (1.4%) required additional vaccine doses. A Syrian origin (p < 0.001) and direct arrival primarily by airplane into Switzerland without transiting through other European countries (p = 0.029) associated with higher anti-TT levels in a multivariate regression model (multiple r2 = 0.210, p < 0.001). A single dose of TTCV is enough to generate long-term protection in most migrant children. In the context of high basic vaccination coverage, the strategy, which consists of administration of a single dose of TTCV followed by anti-TT serology, can be considered where serotesting is available and economical. [ABSTRACT FROM AUTHOR]

Background Worldwide coverage of hepatitis B (HB) vaccination is increasing. This should be considered when determining the best strategy for catch-up HB vaccination in migrant children, who rarely have written proof of past immunizations. This study aimed to estimate HB vaccine protection, chronic HB prevalence and to identify determinants of vaccine protection. Methods Newly arrived migrant children at Lausanne University Hospital from October 2014 to July 2017 were prospectively enrolled. Children and adolescents aged 1–18 years were approached for inclusion if they had no proof of past vaccinations and accepted a single dose of injected HB vaccine. HB surface antibody (anti-HBs) serology was performed after 4–6 weeks. Anti-HBs ≥100 IU/L were considered consistent with a booster-type antibody response. Patients with anti-HBs <100 IU/L received additional dose(s) of HB vaccine, after exclusion of chronic HB in children with anti-HBs <10 IU/L. Potential determinants of vaccine response were compared between children with and without booster-type response. Results Two hundred children were available for analysis. Median age was 8.9 years (IQR 4.8–12.9), and 97 (49%) were female. The majority (n = 124, 62%) came from the region classified by the WHO as eastern Mediterranean. One hundred and sixty-one children (81%) had a booster-type antibody response. Only 1 patient (<1%) had chronic HB. In the multivariate analysis, younger age (OR per decreasing-year, 1.28; 95%CI, 1.05–1.57; p = 0.017) and migration from an urban area (OR 1.16; 95%CI, 1.01–1.33; p = 0.043) were the only significant determinants of booster-type response. Conclusion Post-vaccine serology may be used to identify a high proportion of individuals in our pediatric migrant population with previous immunization for HB. Our study also showed extremely low prevalence of chronic HB. No variable could definitively determine the results of serology. Post-vaccine serology represents the most effective strategy in this context of high vaccine coverage. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To compare antibody responses elicited by influenza A/H1N1/09 disease and immunization with adjuvanted vaccines, in immunocompetent or immunocompromised children. Study design: Prospective parallel cohort field study enrolling children with confirmed influenza A/H1N1/09 disease or immunized with 1 (immunocompetent) or 2 (immunocompromised) doses of influenza A/H1N1/09 squalene-based AS03- or MF59-adjuvanted vaccines. Antibody geometric mean titers (GMT) were measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays 4–6 weeks after vaccination/disease. Vaccine adverse events were self-recorded in a 7-day diary. Results: Antibody titers were as high in 48 immunocompetent children after a single immunization (HAI and MN seroprotection rates: 98%; HAI-GMT: 395, MN-GMT: 370) as in 51 convalescent children (seroprotection rates: 98% (HAI) and 92% (MN); GMT: 350 (HAI) and 212 (MN). Twenty-seven immunocompromised children reached slightly lower seroprotection rates (HAI: 89%, MN: 85%) but similar antibody titers (HAI-GMT: 306, MN-GMT: 225) after 2 immunizations. Adverse events increased with age (P =0.01) and were more frequent with Pandemrix® than Focetria® (P =0.03). Conclusions: Similarly high seroresponses may be expected in immunocompetent children after a single dose of adjuvanted vaccines as responses of convalescent children. Two vaccine doses were sufficient for most immunocompromised children. Trial registration: NCT0102293 and NCT01022905. [Copyright &y& Elsevier]