Parental socioeconomic and psychological determinants of the 2009 pandemic influenza A(H1N1) vaccine uptake in children.

BACKGROUND: Before COVID-19, the previous pandemic was caused by influenza A(H1N1)pdm09 virus in 2009. Identification of factors behind parental decisions to have their child vaccinated against pandemic influenza could be helpful in planning of other pandemic vaccination programmes. We investigated the association of parental socioeconomic and psychosocial factors with uptake of the pandemic influenza vaccine in children in 2009-2010. METHODS: This study was conducted within a prospective birth-cohort study (STEPS Study), where children born in 2008-2010 are followed from pregnancy to adulthood. Demographic and socioeconomic factors of parents were collected through questionnaires and vaccination data from electronic registers. Before and after the birth of the child, the mother's and father's individual and relational psychosocial well-being, i.e. depressive symptoms, dissatisfaction with the relationship, experienced social and emotional loneliness, and maternal anxiety during pregnancy, were measured by validated questionnaires (BDI-II, RDAS, PRAQ, and UCLA). RESULTS: Of 1020 children aged 6-20 months at the beginning of pandemic influenza vaccinations, 820 (80%) received and 200 (20%) did not receive the vaccine against influenza A(H1N1)pdm09. All measures of parents' psychosocial well-being were similar between vaccinated and non-vaccinated children. Children of younger mothers had a higher risk of not receiving the influenza A(H1N1)pdm09 vaccine than children of older mothers (OR 2.59, 95% CI 1.52-4.43, for mothers < 27.7 years compared to ≥ 33.6 years of age). Children of mothers with lower educational level had an increased risk of not receiving the vaccine (OR 1.46, 95% CI 1.00-2.14). CONCLUSIONS: Mother's younger age and lower education level were associated with an increased risk for the child not to receive the 2009 pandemic influenza vaccine, but individual or relational psychosocial well-being of parents was not associated with children's vaccination. Our findings suggest that young and poorly educated mothers should receive targeted support in order to promote children's vaccinations during a pandemic.

Respiratory syncytial virus infections in children 0-24 months of age in the community.

OBJECTIVES: Respiratory syncytial virus (RSV) is a major cause of hospitalization in young children, but there are little data on RSV infections in early childhood in the community. We conducted a prospective population-based birth-cohort study to determine the rates and characteristics of RSV infections in young children. METHODS: We followed 923 children for acute respiratory infections (ARIs) from birth to age 24 months with daily diaries and study clinic visits. Nasal swab samples were obtained at the onset of ARIs and analyzed for RSV by RT-PCR and antigen tests. The rates of RSV infections and associated outcomes were estimated. RESULTS: RSV was detected in 289 (6%) of 4728 ARIs with a nasal sample. The mean estimated annual rate of RSV infections was 37 (95% confidence interval [CI], 35-38) per 100 children at age 0-24 months. For RSV-associated outcomes, the estimated annual rates per 100 children were 34 (95% CI, 32-37) physician visits, 16 (95% CI, 15-17) antibiotic treatments, 12 (95% CI, 11-13) acute otitis media, and 6 (95% CI, 4-7) wheezing illnesses. The prevalence of RSV was 0.6% in asymptomatic children. CONCLUSIONS: RSV infections impose a high burden of disease in healthy young children in the community.

Influenza virus infections from 0 to 2 years of age: A birth cohort study.

BACKGROUND/PURPOSE: Influenza vaccine has been recommended in Finland since 2007 for all children of 6-35 months of age and in 2009 for those ≥6 months against pandemic influenza. We investigated the incidence of influenza and vaccine effectiveness in a birth cohort of children in 2008-2011. METHODS: We followed 923 children from birth to 2 years of age for respiratory tract infections. A nasal swab sample for PCR for influenza A and B viruses was taken at the onset of acute respiratory infections. Samples were collected either at the study clinic or at home by parents. Vaccination data was retrieved from the health registries. RESULTS: Vaccination coverage of children aged 6-23 months was 22-47% against seasonal influenza and 80% against the A(H1N1)pdm09 virus in the pandemic season 2009-2010. During 3 influenza seasons, 1607 nasal swab samples were collected. Influenza was confirmed in 56 (6.1%) of 923 children (16 A(H1N1), 14 A(H3N2), and 26 B viruses). The incidence of influenza was 5.1% in 2008-2009, 2.7% in 2009-2010, and 5.0% in 2010-2011. Effectiveness of the adjuvanted vaccine against the pandemic influenza A(H1N1)pdm09 was 97% (95% confidence interval, 76-100%). Three children with influenza were hospitalized. CONCLUSION: The yearly incidence of seasonal influenza was 5% in this cohort of very young children with variable influenza vaccine coverage. Adjuvanted vaccine against the pandemic influenza was highly effective. Both seasonal and pandemic influenza cases were mostly non-severe.

Effectiveness of the ten-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10) against all respiratory tract infections in children under two years of age.

BACKGROUND: Pneumococcal conjugate vaccines reduce the incidence of invasive pneumococcal diseases, pneumonia, acute otitis media (AOM), and antimicrobial prescriptions in children. We investigated the effectiveness of at least one dose of the ten-valent pneumococcal Haemophilus influenzae protein D conjugate vaccine (PHiD-CV10; GSK) against respiratory tract infections (RTIs) in children under two years of age. METHODS: 424 children enrolled in a cluster-randomized, double-blind Finnish Invasive Pneumococcal disease (FinIP) vaccine trial during the years 2009-2010 were actively followed in a prospective cohort study (STEPS study) for RTIs from birth to two years of age. Children received the PHiD-CV10 vaccine, or a control vaccine (hepatitis A or B vaccine) according to an age-specific schedule. Data on RTIs were collected by symptom diaries, clinic visits, an electronic registry on hospitalizations, and by nasal swab samples analyzed for respiratory viruses. We estimated the vaccine effectiveness against all RTI episodes and RTI episodes with or without AOM by comparing the corresponding incidence rates between PHiD-CV10 vaccinated and control children, adjusted for presence of siblings and cluster as a random effect. RESULTS: A total of 3193 RTI episodes were documented after the first vaccination in 368 children with all data available. The majority of the illnesses were upper RTIs caused by rhinovirus. The PHiD-CV10-vaccinated children had lower mean annual rates of all RTI episodes (6.4; 95% confidence interval [CI], 6.0-6.8) and RTI episodes with AOM (1.0; 95% CI, 0.9-1.2) as compared to the control children (7.4; 95% CI, 6.8-8.0 and 1.3; 95% CI, 1.1-1.6, respectively). The vaccine effectiveness was 12% (95% CI, 2-22%) against all RTIs, 23% (95% CI, 0-40%) against RTIs with AOM, and 10% (95% CI, 0-19%) against RTIs without AOM. CONCLUSIONS: Vaccination with PHiD-CV10 resulted in lower rates of RTIs in children under two years of age compared to children vaccinated with control vaccine.

Serological Array-in-Well Multiplex Assay Reveals a High Rate of Respiratory Virus Infections and Reinfections in Young Children.

Serological assays are used to diagnose and characterize host immune responses against microbial pathogens. Microarray technologies facilitate high-throughput immunoassays of antibody detection against multiple pathogens simultaneously. To improve survey of influenza A virus (IAV), influenza B virus (IBV), respiratory syncytial virus (RSV), and adenovirus (AdV) antibody levels, we developed a microarray consisting of IAV H1N1, IAV H1N1pdm09 (vaccine), IAV H3N2, IBV Victoria, IBV Yamagata, RSV, AdV type 5 hexon protein, and control antigens printed on the bottom of a microtiter plate well. Bound IgG antibodies were detected with anti-human IgG-coated photon-upconverting nanoparticles and measured with a photoluminescence imager. The performance of the microarray immunoassay (MAIA) was evaluated with serum samples (n = 576) collected from children (n = 288) at 1 and 2 years of age and tested by standard enzyme immunoassays (EIAs) for antibodies to IAV vaccine and RSV. EIAs and MAIA showed substantial to almost perfect agreement (Cohen's κ, 0.62 to 0.83). Applying MAIA, we found seroprevalences of 55% for IAV H1N1, 54% for IAV vaccine, 30% for IAV H3N2, 24% for IBV Victoria, 25% for IBV Yamagata, 38% for RSV, and 26% for AdV in 1-year-old children (n = 768). By the age of 2 years, IgG seropositivity rates (n = 714) increased to 74% for IAV H1N1, 71% for IAV vaccine, 49% for IAV H3N2, 47% for IBV Yamagata, 49% for IBV Victoria, 68% for RSV, and 58% for AdV. By analyzing increases in antibody levels not biased by vaccinations, we found a reinfection rate of 40% for RSV and 31% for AdV in children between 1 and 2 years of age.IMPORTANCE The multiplex immunoassay was successfully used to simultaneously detect antibodies against seven different viruses. The developed serological microarray is a new promising tool for diagnostic, epidemiological, and seroprevalence analyses of virus infections.

Burden of Recurrent Respiratory Tract Infections in Children: A Prospective Cohort Study.

BACKGROUND: The burden of recurrent respiratory infections is unclear. We identified young children with recurrent respiratory infections in order to characterize the clinical manifestations, risk factors and short-term consequences. METHODS: In this prospective cohort study, 1089 children were followed from birth to 2 years of age for respiratory infections by a daily symptom diary. Nasal swabs taken during respiratory infections were analyzed for viruses from 714 children. Nasopharyngeal swabs collected at 2 months of age were cultured for bacteria. The 10% of children with the highest number of annual respiratory illness days were defined to have recurrent respiratory tract infections. RESULTS: The 90th percentile in the number of annual respiratory illness days was 98. Children above this limit (n = 109) had a median of 9.6 acute respiratory infections per year. Rhinovirus was detected in 58% of their infections. Of the children with recurrent infections, 60% were diagnosed with at least 3 episodes of acute otitis media, 73% received at least 3 antibiotic treatments and 21% were hospitalized for an acute respiratory infection. Tympanostomy was performed for 35% and adenoidectomy for 13% of the children. Asthma was diagnosed in 12% by 24 months of age. Older siblings increased the risk of recurrent respiratory infections. Early nasopharyngeal colonization with Streptococcus pneumoniae was common in children who later developed recurrent infections. CONCLUSIONS: Children with recurrent respiratory infections frequently use health care services and antibiotics, undergo surgical procedures and are at risk for asthma in early life. Having older siblings increases the risk of recurrent infections.

Rhinovirus Infections in the First 2 Years of Life.

BACKGROUND AND OBJECTIVES: Rhinoviruses frequently cause respiratory infections in young children. We aimed to establish the burden of acute respiratory infections caused by rhinovirus during the first 2 years of life. METHODS: In this prospective birth cohort study, we followed 923 children for acute respiratory infections from birth to 2 years of age. Data on respiratory infections were collected by daily symptom diaries, study clinic visits, and from electronic registries. Respiratory viruses were detected by reverse transcription-polymerase chain reaction and antigen assays during respiratory infections and at the age of 2, 13, and 24 months. The rates of rhinovirus infections and associated morbidities were determined. RESULTS: We documented 8847 episodes of acute respiratory infections, with an annual rate of 5.9 per child (95% confidence interval [CI], 5.7-6.1). Rhinovirus was detected in 59% of acute respiratory infections analyzed for viruses. Rhinovirus was associated with 50% of acute otitis media episodes, 41% of wheezing illnesses, 49% of antibiotic treatments, and 48% of outpatient office visits for acute respiratory infections. The estimated mean annual rate of rhinovirus infections was 3.5 per child (95% CI, 3.3-3.6), 47 per 100 children (95% CI, 42-52) for rhinovirus-associated acute otitis media, and 61 per 100 children (95% CI, 55-68) for rhinovirus-associated antibiotic treatment. The prevalence of rhinovirus at 2, 13, or 24 months of age was 14 to 24%, and 9% of asymptomatic children were positive for rhinovirus. CONCLUSIONS: Rhinovirus infections impose a major burden of acute respiratory illness and antibiotic use on young children.

Pandemic influenza A (H1N1) virus in households with young children.

BACKGROUND: Influenza viruses may cause a severe infection in infants and young children. The transmission patterns of pandemic 2009 influenza A (H1N1) within households with young children are poorly characterized. METHODS: Household members of six children younger than 1·5 years with documented 2009 influenza A (H1N1) infection were studied by daily symptom diaries and serial parent-collected nasal swab samples for detection of influenza A by reverse transcription polymerase chain reaction (RT-PCR) assay. RESULTS: Laboratory-confirmed, symptomatic influenza was documented in 11 of 15 household contacts of young children with pandemic influenza (73%; 95% CI, 48-99). In five contact cases symptoms started earlier, in three cases on the same day, and in three cases after the onset of symptoms in the youngest child. The first case with influenza A (H1N1) within the household was an elder sibling in two households, father in two households, the youngest child in one household, and the youngest child at the same time with a sibling in one household. The median copy number of influenza virus was higher in children than in adults (4·2 × 10(7) versus 4·9 × 10(4), P = 0·02). CONCLUSIONS: This study demonstrates the feasibility of nasal swab sampling by parents in investigation of household transmission of influenza. The results support influenza vaccination of all household contacts of young children.