Influenza vaccine effectiveness in children: a retrospective study on eight post-pandemic seasons with trivalent inactivated vaccine.

BACKGROUND AND AIM OF THE WORK: The global burden of disease attributable to seasonal influenza virus in children is difficult to quantify. Children with chronic medical conditions and healthy children may experience severe or fatal complications. Aim of the study was to estimate the influenza vaccine effectiveness (VE) in a cohort of outpatient children. METHODS: From 2010 to 2018, a Pediatrician of Parma from the InfluNet network of Emilia-Romagna Region, performed nasal/throat swabs on every child with Influenza-like illness at least 14 days from the vaccination with trivalent vaccine. VE estimates against influenza season, virus type and subtype and age group were evaluated using a test-negative design. RESULTS: 2,480 swabs were performed. The 57.6% of the analyzed swabs were positive for influenza viruses. Type A (57%) and type B viruses (43%) co-circulated. The 37.1% of type A viruses belonged to subtype A(H3N2), 19.4% to subtype A(H1N1)pdm09. The subtype A(H3N2) was prevalent among children up to 23 months (42.4%) while the type B in the 2-4 (40.7%) and 5-16 year old age groups (49.4%). Overall, 19.9% of the children were vaccinated. The highest prevalence of vaccinated subjects was found in children aged 5-16 (30.5%). The VE against subtype A(H1N1)pdm09 was 63% (95%CI 42.6-76.0), against type B 27.5% (95%CI 7.9-42.9) and against subtype A(H3N2) -14.3%  (95%CI - 46.0-10.7). CONCLUSIONS: Our findings represent a useful contribution to the ongoing debate about the appropriateness of including influenza vaccination for healthy children, 6 months and older, in the updating National Vaccine Prevention Plan (PNPV).

Immunity status against tetanus in young migrants: a seroprevalence study.

BACKGROUND AND AIM OF THE WORK: Thanks to the highly effective vaccine, tetanus became sporadic in high-income countries with well-established primary childhood immunization programs, but it is common in low-income countries. The migrants, leaving countries with poor immunization programs or where vaccinations have been interrupted, may represent a new risk group for tetanus in host countries. A seroprevalence study was conducted to estimate the immunological status against tetanus in young migrants without vaccination documentation. METHODS: After a careful assessment by vaccination services of the Local Health Authority, all migrants recently arrived in Italy were included in the serosurvey. Titers of anti-tetanus toxoid were measured using a commercial ELISA kit. Subjects were stratified by age and by WHO region. Antibody titers <0.10 IU/ml were considered to be seronegative, between 0.10 and 1.00 IU/ml as intermediate protection, and >1.00 IU/ml high protection. RESULTS: From January 2004 to December 2019, 2,326 blood samples were collected. Mean age was 13.9 years with no differences between WHO regions. The percentage of the subjects without protective antibodies was 22.3%, with an intermediate level was 45.2%, with high titer was 32.5%. Among migrant coming from African and Eastern Mediterranean WHO regions, the highest percentages of seronegative titers and, at the same time, the low percentages of high protective levels were found. Titers decreased with age. CONCLUSIONS: The significant proportion of seronegative migrants and the decrease of protective titers increasing age, confirm the importance of the evaluation of the immunological status to employ the appropriate vaccination strategy.

On field vaccine effectiveness in three periods of 2018/2019 influenza season in Emilia-Romagna Region.

BACKGROUND AND AIM OF THE WORK: Epidemic influenza is associated with significant morbidity and mortality, particularly in people at risk. The vaccine reduces complications, hospitalization and mortality excess, as well as health care and social costs. Aim of the study was to estimate the influenza vaccine effectiveness (VE) in Emilia-Romagna Region during the 2018/2019 season. METHODS: Within the context of virological surveillance conducted at the Regional Reference Laboratory of Parma, nasal/throat swabs were performed by sentinel practitioners and clinicians, on patients with ILI (Influenza-like illness). VE estimates, overall and against subtype A(H1N1)pdm09 and A(H3N2), were evaluated in three periods of the season, using a test-negative case-control design. RESULTS: From November 2018 to April 2019, 2,230 specimens were analyzed: 1,674 (75.1%) performed by clinicians and 556 (24.9%) by sentinel practitioners of the regional network. The season was characterized by the predominant circulation of influenza type A viruses: 57.4% belonged to subtype A(H3N2), 41.2% to subtype A(H1N1)pdm09. 23.5% of patients was vaccinated against influenza with quadrivalent or adjuvate vaccine. The overall VE was -5% (95% CI -33% - 18%) with a decreasing trend during the season. The overall VE against subtype A(H1N1)pdm09 was 39% (95% CI 11% - 58%) and remained stable during the season. The overall VE against subtype A(H3N2) was -43% (95% CI -89% - -9%), and showed an important decreasing trend. CONCLUSIONS: The possibility to make accurate and continuous VE estimates during the season will help to better define the composition of the vaccine for the following season.

Immunity status against poliomyelitis in young migrants: a seroprevalence study.

BACKGROUND AND AIM OF THE WORK: Recent seroprevalence studies in different population groups have shown low antibody titers against poliomyelitis, especially in young adults. This, together with the reduction of vaccination rates, could favor the reintroduction of poliovirus in long-time polio-free countries. Within the Surveillance system of acute flaccid paralysis, a prevalence study was conducted to estimate the immunological status associated with poliomyelitis in young migrants. METHODS: Local Health Authority collected serum samples in young migrants, without vaccination documentation. Antibodies levels were assessed with a long incubation neutralization assay. Subjects were stratified by age and by WHO region. Seroprotection was defined by a titer equal or above 1:8 and titers > 1:2 were log-transformed and evaluated as geometric mean titers (GMTs). RESULTS: From January 2004 to August 2017, 1138 blood samples were collected. Mean age was 13.3 years with no differences between WHO regions. The percentage of antibody titers below 1:8 was 6.0% versus poliovirus 1 (PV1), 7.7% versus poliovirus 2 (PV2) and 15% versus poliovirus 3 (PV3). The GMTs were 45.5, 29.5 and 20 towards PV1, PV2 and PV3 respectively. In each WHO region, the GMTs towards PV3 were consistently the lowest, and the Europeans showed the lowest GMTs both towards PV2 and PV3 (27.5 and 15.3 respectively). GMTs decreased with age. CONCLUSION: The low GMTs and the clear tendency to decrease with increasing age of the subjects, especially against to PV1, confirm the framework of attention that polio is receiving at national and international level.

Virological Surveillance of Influenza in the eight epidemic seasons after the 2009 pandemic in Emilia-Romagna (Northern Italy).

BACKGROUND AND AIM OF THE WORK: Influenza virological surveillance is essential for monitoring the evolution of influenza viruses (IVs) as well as for annual updating of the vaccine composition. The aim of this study is to analyse IVs circulation in Emilia-Romagna during the eight epidemic seasons after the 2009 pandemic and to evaluate their match with seasonal vaccine strains. METHODS: A total of 7882 respiratory specimens from patients with influenza-like illness (ILI), were collected by regional sentinel practitioners and hospital physicians. Viral investigations were conducted by rRT-PCR assay. Genetic characterization was performed for a spatial-temporal representative number of influenza laboratory-confirmed specimens. RESULTS: Influenza-positive samples per season ranged between 28.9% (2013-2014) and 66.8% (2012-2013). Co-circulation of IVs type A and type B was observed in all seasons, although with a different intensity. In all seasons, the highest number of positive samples was recorded in younger patients aged 5-14 years with relative frequencies ranging from 40% in the 2013-2014 season and 78% in the 2012-2013 season. Since the 2009 pandemic, A/H1N1pdm09 IVs circulating were closely related to the vaccine strain A/California/7/2009. Antigenic mismatch between vaccine strain and A/H3N2 IVs was observed in the 2011-2012 and 2014-2015 seasons. During 2015-2016, 2016-2017 and 2017-2018 seasons a complete or nearly complete mismatch between the predominant influenza B lineage of IVs type B circulating and vaccine B lineage occurred. CONCLUSIONS: This analysis confirms the importance of the virological surveillance and highlights the need of a continuous monitoring of IVs circulation, to improve the most appropriate vaccination strategies. (www.actabiomedica.it).

Status of immunity against poliomyelitis: a study among European and extra-European young immigrants living in Parma.

From January 2001 to December 2003 blood specimens obtained from 323 European and extra-European young immigrants were collected for the determination of anti-polio antibody levels. They were sent to the Section of Hygiene, Department of Public Health, by the Local Health Authorities. A neutralization assay was performed to detect the anti-polio antibodies against serotypes 1, 2 and 3, using rhesus monkey kidney cells. The results showed 98,1% prevalence of anti-polio 1 antibodies (titre > or =1:2), 99,1% of anti-polio 2, and 98,8% prevalence of anti-polio 3 antibodies. The seronegativity against only one or two serotypes (antibody titre <1:2) was found in 9 subjects (2,8%) while no subject was found totally seronegative against all 3 serotypes. According to the total amount of the analyzed samples, the estimated Geometric Mean Titre (GMT) resulted from moderate to low (GMT=29 of serotype 3; GMT=48,4 of serotype 2; GMT=56,5 of serotype 1) and it appeared to be similar to the results obtained in the previous years for all 3 serotypes; the GMT of serotype 3 was still the lowest. No difference was observed in the specimens with respect to the country of origin of the examined subjects and the data collected showed a good level of immunity.