Influenza-like Illness Episodes Research Articles

Prevalence and Incidence of Respiratory Syncytial Virus and Other Respiratory Viral Infections in Children Aged 6 Months to 10 Years With Influenza-like Illness Enrolled in a Randomized Trial.

The high burden of respiratory syncytial virus (RSV)-associated morbidity and mortality makes vaccine development a priority. As part of an efficacy trial of pandemic influenza vaccines (NCT01051661), RSV epidemiology in healthy children aged 6 months to <10 years at first vaccination with influenza-like illness (ILI) was evaluated in Australia, Brazil, Colombia, Costa Rica, Mexico, the Philippines, Singapore, and Thailand between February 2010 and August 2011. Active surveillance for ILI was conducted for approximately 1 year, with nasal and throat swabs analyzed by polymerase chain reaction. The prevalence and incidence of RSV among ILI episodes were calculated. A total of 6266 children were included, of whom 2421 experienced 3717 ILI episodes with a respiratory sample available. RSV was detected for 359 ILI episodes, a prevalence of 9.7% (95% confidence interval: 8.7-10.7). The highest prevalence was in children aged 12-23 or 24-35 months in all countries except the Philippines, where it was in children aged 6-11 months. The incidence of RSV-associated ILI was 7.0 (6.3-7.7) per 100 person-years (PY). Eighty-eight ILI episodes resulted in hospitalization, of which 8 were associated with RSV (prevalence 9.1% [4.0-17.1]; incidence 0.2 [0.1-0.3] per 100 PY). The incidence of RSV-associated ILI resulting in medical attendance was 6.0 (5.4-6.7) per 100 PY. RSV B subtypes were observed more frequently than A subtypes. Active surveillance demonstrated the considerable burden of RSV-associated illness that would not be identified through hospital-based surveillance, with a substantial part of the burden occurring in older infants and children.

High rate of A(H1N1)pdm09 infections among rural Thai villagers, 2009-2010.

BackgroundPandemic influenza A(H1N1)pdm09 emerged in Thailand in 2009. A prospective longitudinal adult cohort and household transmission study of influenza-like illness (ILI) was ongoing in rural Thailand at the time of emergence. Symptomatic and subclinical A(H1N1)pdm09 infection rates in the cohort and among household members were evaluated.MethodsA cohort of 800 Thai adults underwent active community-based surveillance for ILI from 2008–2010. Acute respiratory samples from ILI episodes were tested for A(H1N1)pdm09 by qRT-PCR; acute and 60-day convalescent blood samples were tested by A(H1N1)pdm09 hemagglutination inhibition assay (HI). Enrollment, 12-month and 24-month follow-up blood samples were tested for A(H1N1)pdm09 seroconversion by HI. Household members of influenza A-infected cohort subjects with ILI were enrolled in household transmission investigations in which day 0 and 60 blood samples and acute respiratory samples were tested by either qRT-PCR or HI for A(H1N1)pdm09. Seroconversion between annual blood samples without A(H1N1)pdm09-positive ILI was considered as subclinical infection.ResultsThe 2-yr cumulative incidence of A(H1N1)pdm09 infection in the cohort in 2009/2010 was 10.8% (84/781) with an annual incidence of 1.2% in 2009 and 9.7% in 2010; 83.3% of infections were subclinical (50% in 2009 and 85.9% in 2010). The 2-yr cumulative incidence was lowest (5%) in adults born ≤1957. The A(H1N1)pdm09 secondary attack rate among household contacts was 47.2% (17/36); 47.1% of these infections were subclinical. The highest A(H1N1)pdm09 secondary attack rate among household contacts (70.6%, 12/17) occurred among children born between 1990 and 2003.ConclusionSubclinical A(H1N1)pdm09 infections in Thai adults occurred frequently and accounted for a greater proportion of all A(H1N1)pdm09 infections than previously estimated. The role of subclinical infections in A(H1N1)pdm09 transmission has important implications in formulating strategies to predict and prevent the spread of A(H1N1)pdm09 and other influenza virus strains.

Gastrointestinal and respiratory illness in children that do and do not attend child day care centers: a cost-of-illness study.

BackgroundGastrointestinal and respiratory diseases are major causes of morbidity for young children, particularly for those children attending child day care centers (DCCs). Although both diseases are presumed to cause considerable societal costs for care and treatment of illness, the extent of these costs, and the difference of these costs between children that do and do not attend such centers, is largely unknown.ObjectiveEstimate the societal costs for care and treatment of episodes of gastroenteritis (GE) and influenza-like illness (ILI) experienced by Dutch children that attend a DCC, compared to children that do not attend a DCC.MethodsA web-based monthly survey was conducted among households with children aged 0–48 months from October 2012 to October 2013. Households filled-in a questionnaire on the incidence of GE and ILI episodes experienced by their child during the past 4 weeks, on the costs related to care and treatment of these episodes, and on DCC arrangements. Costs and incidence were adjusted for socioeconomic characteristics including education level, nationality and monthly income of parents, number of children in the household, gender and age of the child and month of survey conduct.ResultsChildren attending a DCC experienced higher rates of GE (aIRR 1.4 [95%CI: 1.2–1.9]) and ILI (aIRR: 1.4 [95%CI: 1.2–1.6]) compared to children not attending a DCC. The societal costs for care and treatment of an episode of GE and ILI experienced by a DCC-attending child were estimated at €215.45 [€115.69–€315.02] and €196.32 [€161.58–€232.74] respectively, twice as high as for a non-DCC-attending child. The DCC-attributable economic burden of GE and ILI for the Netherlands was estimated at €25 million and €72 million per year.ConclusionsAlthough children attending a DCC experience only slightly higher rates of GE and ILI compared to children not attending a DCC, the costs involved per episode are substantially higher.

Incidence and risk factors for influenza-like-illness in the UK: online surveillance using Flusurvey.

BackgroundInfluenza and Influenza-like-illness (ILI) represents a substantial public health problem, but it is difficult to measure the overall burden as many cases do not access health care. Community cohorts have the advantage of not requiring individuals to present at hospitals and surgeries and therefore can potentially monitor a wider variety of cases. This study reports on the incidence and risk factors for ILI in the UK as measured using Flusurvey, an internet-based open community cohort.MethodsUpon initial online registration participants were asked background characteristics, and every week were asked to complete a symptoms survey. We compared the representativeness of our sample to the overall population. We used two case definitions of ILI, which differed in whether fever/chills was essential. We calculated ILI incidence week by week throughout the season, and investigated risk factors associated with ever reporting ILI over the course of the season. Risk factor analysis was conducted using binomial regression.Results5943 participants joined the survey, and 4532 completed the symptoms survey at least twice. Participants who filled in symptoms surveys at least twice filled in a median of nine symptoms surveys over the course of the study. 46.1% of participants reported at least one episode of ILI, and 6.0% of all reports were positive for ILI. Females had slightly higher incidence, and individuals over 65 had the lowest incidence. Incidence peaked just before Christmas and declined dramatically during school holidays. Multivariate regression showed that, for both definitions of ILI considered, being female, unvaccinated, having underlying health issues, having contact with children, being aged between 35 and 64, and being a smoker were associated with the highest risk of reporting an ILI. The use of public transport was not associated with an increased risk of ILI.ConclusionsOur results show that internet based surveillance can be used to measure ILI and understand risk factors. Vaccination is shown to be linked to a reduced risk of reporting ILI. Taking public transport does not increase the risk of reporting ILI. Flusurvey and other participatory surveillance techniques can be used to provide reliable information to policy makers in nearly real-time.

Internet-based syndromic monitoring of acute respiratory illness in the general population of Germany, weeks 35/2011 to 34/2012

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Respiratory Syncytial Virus and Other Respiratory Viral Infections in Older Adults With Moderate to Severe Influenza-like Illness

Background. Few studies have prospectively assessed viral etiologies of acute respiratory infections in community-based elderly individuals. We assessed viral respiratory pathogens in individuals ≥65 years with influenza-like illness (ILI). Methods. Multiplex reverse-transcriptase polymerase chain reaction identified viral pathogens in nasal/throat swabs from 556 episodes of moderate-to-severe ILI, defined as ILI with pneumonia, hospitalization, or maximum daily influenza symptom severity score (ISS) >2. Cases were selected from a randomized trial of an adjuvanted vs nonadjuvanted influenza vaccine conducted in elderly adults from 15 countries. Results. Respiratory syncytial virus (RSV) was detected in 7.4% (41/556) moderate-to-severe ILI episodes in elderly adults. Most (39/41) were single infections. There was a significant association between country and RSV detection (P = .004). RSV prevalence was 7.1% (2/28) in ILI with pneumonia, 12.5% (8/64) in ILI with hospitalization, and 6.7% (32/480) in ILI with maximum ISS > 2. Any virus was detected in 320/556 (57.6%) ILI episodes: influenza A (104/556, 18.7%), rhinovirus/enterovirus (82/556, 14.7%), coronavirus and human metapneumovirus (each 32/556, 5.6%). Conclusions. This first global study providing data on RSV disease in ≥65 year-olds confirms that RSV is an important respiratory pathogen in the elderly. Preventative measures such as vaccination could decrease severe respiratory illnesses and complications in the elderly.

Incidence of influenza-like illness into a cohort of patients affected by chronic inflammatory rheumatism and treated with biological agents

This study aimed to evaluate the incidence of influenza-like illness (ILI), from October 2009 to May 2010, in a group of patients suffering from chronic inflammatory rheumatism and treated with biological therapies. At the end of 2009-2010 influenza season, 159 patients under biological therapies answered to a questionnaire distributed 8 months before and were deeply interviewed. The group included 69 men and 90 women (mean age 47.6); forty-nine suffering from rheumatoid arthritis, 61 with psoriatic arthritis, 32 with ankylosing spondylitis and 17 with other spondyloarthritis; 146 patients were treated with anti-TNF-α, 7 with rituximab and 6 with abatacept; 128 patients assumed DMARDs and 72 patients assumed low dose of steroids. A case of ILI was identified by anamnestic findings and according to the case definitions commonly used in Europe. Seventeen percent of the considered population reported at least one episode of ILI during the monitoring period; none of the patients during the acute influenza attack suffered particularly severe symptoms and no one was hospitalized due to complications. Despite the diversity among the considered subgroups, the statistical analysis did not show any significant difference when incidence of ILI was considered for different disease, different biological agent and different association therapy. None of the examined variables resulted statistically significant concerning the relative risk evaluation. The incidence of ILI into a cohort of 159 patients treated with biological agents during the influenza season 2009-2010 resulted higher than the value reported in a wide sample of Italian population in the same period. However, the pandemic impact was not heavy among the studied patients, considering that no important complications or hospitalizations have been reported.

Household transmission of respiratory viruses – assessment of viral, individual and household characteristics in a population study of healthy Australian adults

BackgroundHousehold transmission of influenza-like illness (ILI) may vary with viral and demographic characteristics. We examined the effect of these factors in a population-based sample of adults with ILI.MethodsWe conducted a prospective cohort study in community-dwelling Australian adults nested within an influenza vaccine effectiveness trial. On presentation with ILI, participants were swabbed for a range of respiratory viruses and asked to return a questionnaire collecting details of household members with or without similar symptoms. We used logistic and Poisson regression to assess the key characteristics of household transmission.Results258 participants from multi-occupancy households experienced 279 ILI episodes and returned a questionnaire. Of these, 183 were the primary case in the household allowing assessment of factors associated with transmission. Transmission was significantly associated in univariate analyses with female sex (27% vs. 13%, risk ratio (RR) = 2.13 (1.08, 4.21)) and the presence of a child in the house (33% vs. 17%, RR = 1.90 (1.11, 3.26)). The secondary household attack proportion (SHAP) was 0.14, higher if influenza was isolated (RR = 2.1 (1.0, 4.5)). Vaccinated participants who nonetheless became infected with influenza had a higher SHAP (Incidence RR = 5.24 (2.17, 12.6)).ConclusionsThe increased SHAP in households of vaccinated participants who nonetheless had confirmed influenza infection supports the hypothesis that in years of vaccine mismatch, not only is influenza vaccine less protective for the vaccine recipient, but that the population’s immunity is also lower.

Effectiveness of the 2010–2011 seasonal influenza vaccine in preventing confirmed influenza hospitalizations in adults: A case–case comparison, case-control study

IntroductionWe estimated influenza vaccine effectiveness (IVE) to prevent laboratory-confirmed influenza-related hospitalizations in patients 18 years old or older during the 2010–2011 influenza season. MethodsWe conducted a prospective case-control study in five hospitals, in Valencia, Spain. Study subjects were consecutive emergency hospitalizations for predefined conditions associated with an influenza-like illness episode <8 days before admission. Patients were considered immunized if vaccinated ≥14 days before influenza-like illness onset. Cases were those with a real time reverse transcriptase polymerase chain reaction (RT-PCR) positive for influenza and controls were RT-PCR positive for other respiratory viruses. Adjusted IVE was estimated as 100×(1−adjusted odds ratio). To account for indication bias we computed adjusted IVE for respiratory syncytial virus related hospitalizations. ResultsOf 826 eligible hospitalized patients, 102 (12%) were influenza positive and considered cases, and 116 (14%) were positive for other respiratory viruses and considered controls. Adjusted IVE was 54% (95% confidence interval, 11–76%). By subgroup, adjusted IVE was 53% (4–77%) for those with high-risk conditions, 59% (16–79%) for those ≥60 years of age, and, 54% (4–79%) for those ≥60 years of age with high-risk conditions. No influenza vaccine effect was observed against respiratory syncytial virus related hospitalization. ConclusionInfluenza vaccination was associated with a significant reduction on the risk of confirmed influenza hospitalization, irrespective of age and high-risk conditions.

Epidemiology of Human Metapneumovirus in a Pediatric Long-Term Care Facility

Viral respiratory pathogens cause outbreaks in pediatric long-term care facilities (LTCFs), but few studies have used viral diagnostic testing to identify the causative pathogens. We describe the use of such testing during a prolonged period of respiratory illness and elucidate the epidemiology of human metapneumovirus (hMPV) at our LTCF. Retrospective study of influenza-like illness (ILI). A 136-bed pediatric LTCF from January 1 through April 30, 2010. The ILI case definition included fever, cough, change in oropharyngeal secretions, increase in oxygen requirement, and/or wheezing. During the study period, 69 episodes of ILI occurred in 61 (41%) of 150 residents. A viral pathogen was detected in 27 (39%) of the episodes, including respiratory syncytial virus (RSV) (n = 3), influenza A virus (not typed; n = 2), parainfluenza virus (n =2), adenovirus (n = 1), and hMPV (n = 19). Twenty-seven of the residents with ILI (44%) required transfer to acute care hospitals (mean length of hospitalization, 12 days; range, 3-47 days). Residents with tracheostomies were more likely to have ILI (adjusted odds ratio [OR], 3.99 [95% confidence interval {CI}, 1.87-8.53]; P = .0004). The mortality rate for residents with ILI was 1.6%. Residents with hMPV were younger (P = .03), more likely to be transferred to an acute care facility (OR, 3.73 [95% CI, 1.17-11.95]; P = .02), and less likely to have a tracheostomy (adjusted OR, 0.19 [95% CI, 0.047-0.757]; P = .02 ). Diverse pathogens, most notably hMPV, caused ILI in our pediatric LTCF during a prolonged period of time. Viral testing was helpful in characterizing the epidemiology of ILI in this population.

Maternal Influenza Vaccination and Effect on Influenza Virus Infection in Young Infants

It is recommended that pregnant women receive influenza vaccine because of their increased risk for influenza complications. Several prospective US-based observational studies concluded that maternal influenza vaccination delays the age at first infection and reduces severity of influenza illness; one randomized trial reported that vaccination reduced the incidence of laboratory-confirmed influenza. This nonrandomized, prospective, observational cohort study investigated the effect of seasonal influenza vaccination in pregnant women on the occurrence of influenza virus infection in infants to 6 months of age. Participants were 1160 mother-infant pairs with mothers who delivered one infant during 3 influenza seasons between 2002 and 2005 at the Navajo and White Mountain Apache Indian reservations. Serum specimens from the infants of women who were unvaccinated (n = 587) and vaccinated (n = 573) were collected and analyzed. The primary study outcome measures in infants were laboratory-confirmed influenza, with influenza-like illness (ILI), ILI hospitalization, and elevated influenza hemagglutinin inhibition antibody titers. Among the 1160 infants, 193 (17%) were hospitalized for ILI, 412 (36%) had only an outpatient ILI visit, and 555 (48%) had no ILI episodes. The ILI incidence rate was 7.2 per 1000 person-days for infants born to unvaccinated women and 6.7 per 1000 person-days for those born to vaccinated women. Compared with infants of unvaccinated women, there was a 41% reduction in the risk of laboratory-confirmed influenza virus infection (relative risk, 0.59; 95% confidence interval, 0.37–0.93) and a 39% reduction in the risk of hospitalization for ILI (relative risk, 0.61; 95% confidence interval, 0.45–0.84) among infants of vaccinated women. Moreover, hemagglutinin inhibition antibody titers to each of the 8 influenza virus antigens tested at birth and at 2 to 3 months of age were significantly higher in infants born to mothers vaccinated during pregnancy. These findings show that maternal influenza vaccination increased influenza antibody titers in infants through 2 to 3 months of age, reducing their risk of both influenza virus infection and ILI hospitalization during the first 6 months of life. These data demonstrate the public health importance of maternal influenza vaccination.

A population-based study on incidence and economic burden of influenza-like illness in south China, 2007

The disease burden of influenza-like illness (ILI) in most tropical and subtropical countries has not been described adequately to date. The aim of this study was to determine the epidemiology and incidence of ILI, and to assess the economic burden in south China. Prospective study. A population-based household survey was conducted quarterly in 2007 in Guangdong Province. The average number of subjects in each quarterly survey was 13,687. In total, 1002 cases of self-reported ILI were identified in all four surveys, indicating an annual incidence of 7.23 cases of ILI per 100 persons. The second quarter had the highest incidence of ILI (2.83 cases per 100 persons). Children aged 1-4 years, <1 year and 5-9 years had the highest annual incidence rates of ILI (49.87, 35.19 and 21.24 cases per 100 persons, respectively). The incidence of ILI was significantly higher in males than females (P<0.001), and significantly higher in rural residents than urban residents (P<0.001). The individual cost per episode of ILI represented approximately 20% of monthly per-capita income of residents. The results of this large-scale household study confirm that ILI places a substantial health and economic burden on south China. Ultimately, the results of this study will provide further information for understanding the disease burden of influenza in subtropical areas.

Impaired Response to Influenza Vaccine Associated with Persistent Memory B Cell Depletion in Non-Hodgkin’s Lymphoma Patients Treated with Rituximab-Containing Regimens

Influenza vaccination is generally recommended for non-Hodgkin's lymphoma (NHL) patients, but no data are available about the activity of this vaccine after treatment with rituximab-containing regimens. We evaluated the humoral response to the trivalent seasonal influenza vaccine in a group of NHL patients in complete remission for ≥6 mo (median, 29 mo) after treatment with rituximab-containing regimens (n = 31) compared with age-matched healthy subjects (n = 34). B cell populations and incidence of influenza-like illness were also evaluated. For each viral strain, the response was significantly lower in patients compared with controls and was particularly poor in patients treated with fludarabine-based regimens. In the patient group, the response to vaccination did not fulfill the immunogenic criteria based on the European Committee for Medicinal Products for Human Use requirements. Among the patients, CD27(+) memory B cells were significantly reduced, and their reduction correlated with serum IgM levels and vaccine response. Episodes of influenza-like illness were recorded only in patients. These results showed that NHL patients treated with rituximab-containing regimens have persisting perturbations of B cell compartments and Ig synthesis and may be at particular risk for infection, even in long-standing complete remission.

Clinical manifestations and socio-economic impact of influenza among healthy children in the community

To evaluate the total burden of influenza among healthy children in the community in order to analyse the cost of influenza in paediatric age. This prospective study involved a total community population of 21,986 children, 6988 of whom experienced an influenza-like illness (ILI) between 1 November 2008 and 30 April 2009. An electronic chart was completed, a nasopharyngeal swab was obtained, and information was recorded concerning the clinical outcomes and household impact of the ILI episodes. Influenza A and B viruses were detected in all the swabs by means of polymerase chain reaction, and costs of the disease were calculated. Influenza viruses were detected in 2143 cases (30.7%), an incidence of 96.4 per 1000 children. Influenza A and B viruses were found in respectively 1751 (81.7%) and 392 cases (18.3%). The mean cost of influenza was no less than €130, 32% higher than the cost of influenza-negative ILIs (p < 0.001). The influenza A cases were significantly more expensive than the influenza B cases (p < 0.001), and influenza in children aged <2 and 2-5 years was significantly more expensive than in children aged >5 years (p < 0.05). The differences were mainly related to the indirect costs of the parents' lost working days. The findings of this study confirm that influenza among healthy children is important because of its frequency and its indirect consequences on the households of infected children, and support the use of influenza vaccination in healthy children aged between 6 months and 5 years.

Influenza Vaccination in Healthy Working Adults in Russia

All age groups are affected by influenza infection, resulting in significant medical and economic burden. Influenza infection of healthy working adults can have a marked effect on companies due to lost work days and reduced productivity. Studies in corporate settings have shown that vaccination programmes reduce this burden, although there is a lack of data in Eastern European countries. To determine the effectiveness of influenza vaccination in healthy working adults in Russia and the economic benefits of such a programme from an employer's perspective. In a prospective, non-randomized, non-placebo-controlled, observational study, healthy vaccinated and unvaccinated adults employed at the Russian Railways Public Corporation were followed for 8 months during the 2005-6 influenza season using questionnaires. A first questionnaire was administered at inclusion to collect general employee information; a second questionnaire was administered to collect data on post-vaccination adverse events; and monthly questionnaires were used to gather data on influenza-like illness (ILI). Effectiveness calculations and cost analyses were performed to evaluate the impact of the influenza vaccination programme on employee productivity and costs for the employer. The study vaccine used was the trivalent, inactivated, split vaccine Vaxigrip® (sanofi pasteur, France). A total of 1331 employees volunteered for the study: 701 were vaccinated and 630 were not. The vaccine effectiveness was 70.4% against ILI events and 80.8% against sick leave days. Assuming that employees working with ILI symptoms had a reduced level of productivity (30-70% of normal), cost savings per vaccinated employee ranged from &U20AC;2.13 to &U20AC;5.43. This study showed that an influenza vaccination programme significantly reduced ILI episodes and absenteeism, and may provide a positive return on investment for the employer.

Vaccination against the 2009 pandemic influenza A (H1N1) among healthcare workers in the major teaching hospital of Sicily (Italy)

The aim of the study was to investigate factors involved in vaccination acceptance among healthcare workers (HCWs) and adverse reactions rates associated with pandemic influenza vaccination. The study was carried out in the major teaching hospital of Sicily from November 2009 to February 2010 on 2267 HCWs. A total of 407 (18%) HCWs were vaccinated against the 2009 pandemic influenza A (H1N1). A logistic regression analysis indicates an increased risk of non-vaccination against pandemic influenza in females (OR=1.6; 95% CI=1.3–2.1) compared to males, in nurses/technicians/administrative workers (OR=1.7; 95% CI=1.3–2.2) compared to doctors/biologists, and in HCWs who were non-vaccinated against seasonal influenza in 2008–2009 (OR=4.9; 95% CI=3.7–6.5) compared to vaccinated HCWs. Overall, 302 (74.2%) out of 407 questionnaires distributed to vaccinated HCWs were returned within the observation period. One hundred fifty-two workers (50.3%) experienced at least one adverse reaction (30.1%, local reactions; 6.6% systemic reactions and 13.6% both of them). The most frequent side effect of vaccination was pain at the injection site (43.4%). Twelve (3.9%) out of 302 HCWs stated they experienced influenza-like illness episodes during the follow-up period. The use of an adjuvanted vaccine against pandemic influenza A (H1N1) appears to be an effective and safe preventive strategy, showing a prevalence of both local and systemic adverse reactions not very different from that seen after vaccination with non-adjuvanted seasonal influenza vaccine. Despite this finding, vaccination coverage among HCWs remains very low, suggesting the need to implement educational campaigns directed to groups with lower coverage rates.

Modeling Competing Infectious Pathogens From a Bayesian Perspective: Application to Influenza Studies With Incomplete Laboratory Results

In seasonal influenza epidemics, pathogens such as respiratory syncytial virus (RSV) often cocirculate with influenza and cause influenza-like illness (ILI) in human hosts. However, it is often impractical to test for each potential pathogen or to collect specimens for each observed ILI episode, making inference about influenza transmission difficult. In the setting of infectious diseases, missing outcomes impose a particular challenge because of the dependence among individuals. We propose a Bayesian competing-risk model for multiple cocirculating pathogens for inference on transmissibility and intervention efficacies under the assumption that missingness in the biological confirmation of the pathogen is ignorable. Simulation studies indicate a reasonable performance of the proposed model even if the number of potential pathogens is misspecified. They also show that a moderate amount of missing laboratory test results has only a small impact on inference about key parameters in the setting of close contact groups. Using the proposed model, we found that a nonpharmaceutical intervention is marginally protective against transmission of influenza A in a study conducted in elementary schools.

Influenza vaccine for healthy adult workers: An issue for health authorities or employers?

Objective To contribute to the debate whether extending public coverage of influenza vaccination to healthy workers is cost-effective, particularly in the perspective of EU countries. Methods First, we reviewed the recent international literature on the extension of vaccination to subjects aged 50–64 years in highly developed countries. Second, we estimated the broad economic impact of influenza vaccination on the Italian healthy adult working population. Finally, we ran a pilot observational study to assess the healthcare and labour outcomes of influenza vaccination on the employees of our organization. Results The methodological weaknesses of the studies reviewed, all built on models, undermine the credibility of their optimistic results. The more cautious the model design, the less favourable the final results, as our conservative analysis on the Italian setting confirmed. The only common result was a steady relationship between potential vaccination benefits and indirect costs of absenteeism from work. This “modelling-based evidence” was confirmed by our internal survey: vaccinated workers showed less tendency to stay at home during influenza-like illness episodes and their relapses. Conclusions The economic advantage of extending public influenza vaccination to healthy adult workers is still uncertain and mainly relates to the indirect costs of productivity losses, making the extension strategy more a labour than a health issue.

Maternal Influenza Vaccination and Effect on Influenza Virus Infection in Young Infants

To assess the effect of seasonal influenza vaccination during pregnancy on laboratory-confirmed influenza in infants to 6 months of age. Nonrandomized, prospective, observational cohort study. Navajo and White Mountain Apache Indian reservations, including 6 hospitals on the Navajo reservation and 1 on the White Mountain Apache reservation. A total of 1169 mother-infant pairs with mothers who delivered an infant during 1 of 3 influenza seasons. Maternal seasonal influenza vaccination. In infants, laboratory-confirmed influenza, influenza-like illness (ILI), ILI hospitalization, and influenza hemagglutinin inhibition antibody titers. A total of 1160 mother-infant pairs had serum collected and were included in the analysis. Among infants, 193 (17%) had an ILI hospitalization, 412 (36%) had only an ILI outpatient visit, and 555 (48%) had no ILI episodes. The ILI incidence rate was 7.2 and 6.7 per 1000 person-days for infants born to unvaccinated and vaccinated women, respectively. There was a 41% reduction in the risk of laboratory-confirmed influenza virus infection (relative risk, 0.59; 95% confidence interval, 0.37-0.93) and a 39% reduction in the risk of ILI hospitalization (relative risk, 0.61; 95% confidence interval, 0.45-0.84) for infants born to influenza-vaccinated women compared with infants born to unvaccinated mothers. Infants born to influenza-vaccinated women had significantly higher hemagglutinin inhibition antibody titers at birth and at 2 to 3 months of age than infants of unvaccinated mothers for all 8 influenza virus strains investigated. Maternal influenza vaccination was significantly associated with reduced risk of influenza virus infection and hospitalization for an ILI up to 6 months of age and increased influenza antibody titers in infants through 2 to 3 months of age.

Original Article: Assessing physicians’ in training attitudes and behaviors during the 2009 H1N1 influenza season: a cross‐sectional survey of medical students and residents in an urban academic setting

Despite concern for hospital-based transmission of influenza, little research has been carried out on perceptions and behaviors of physicians in training with regard to influenza-like illness (ILI), especially in light of the recent H1N1 pandemic. We aimed to evaluate self-reported episodes of ILI among medical students and residents to determine the impact of ILI on school and clinical performance, absenteeism, and patterns of preventive measures used by this population both in and out of the healthcare setting. We anonymously surveyed medical students and residents at an urban institution between November 3 and December 11, 2009. Data were analyzed separately for medical students and residents for frequency of close-ended responses. Open-ended answers were analyzed thematically. Our Institutional Review Board exempted this study from review. Forty-five percent of medical students and 53% of resident respondents perceived the risk of acquiring H1N1 at school or work as high, and although 43% of medical students and 66% of resident respondents had received the influenza vaccination and most reported increasing non-pharmaceutical preventive measures, 9% of medical students and 61% of residents with one or more episodes of ILI chose to continue to attend class or work when ill. Although students and residents report high risk of infection because of work- or school-related activities, many involved in patient care activities do not comply with recommended infection control precautions. Educational campaigns should be developed and infection control guidelines should be included in routine medical student and resident curricular activities.