Influenza-associated Hospitalizations Research Articles

Effects of Air Pollution and Other Environmental Exposures on Estimates of Severe Influenza Illness, Washington, USA.

Ecologic models of influenza burden may be confounded by other exposures that share winter seasonality. We evaluated the effects of air pollution and other environmental exposures in ecologic models estimating influenza-associated hospitalizations. We linked hospitalization data, viral surveillance, and environmental data, including temperature, relative humidity, dew point, and fine particulate matter for 3 counties in Washington, USA, for 2001–2012. We used negative binomial regression models to estimate the incidence of influenza-associated respiratory and circulatory (RC) hospitalizations and to assess the effect of adjusting for environmental exposures on RC hospitalization estimates. The modeled overall incidence rate of influenza-associated RC hospitalizations was 31/100,000 person-years. The environmental parameters were statistically associated with RC hospitalizations but did not appreciably affect the event rate estimates. Modeled influenza-associated RC hospitalization rates were similar to published estimates, and inclusion of environmental covariates in the model did not have a clinically important effect on severe influenza estimates.

Effectiveness of influenza vaccine in reducing influenza-associated hospitalizations and deaths among the elderly population; Lazio region, Italy, season 2016-2017

ABSTRACT Background This study aimed to estimate influenza vaccine effectiveness (VE) in preventing influenza-related deaths and hospitalizations in the elderly population. Methods We retrospectively analyzed the cohort of 1,251,218 elderly aged ≥65 years who were residing in the Lazio region in 2016–2017. We estimated influenza VE using the Cox proportional hazards model, adjusting for demographic characteristics, preexisting health-risk conditions, and prior vaccinations. Results Estimated VE was 14% (95% confidence interval (CI): 11 to 17); 26% (95%CI: 19 to 33) in preventing influenza-related deaths and 13% (95%CI: 10 to 16) in preventing influenza-related hospitalizations. Seasonal VE was higher in the elderly vaccinated in prior seasons (VE = 20%, 95%CI: 17 to 23). We found no significant differences in effectiveness by vaccine type, although the MF59-adjuvanted vaccine appeared more effective than other vaccines in individuals aged ≥75 years, particularly in those aged ≥90 years (VE = 18%, 95%CI: 9 to 26). Conclusions Although VE was low, vaccination still provided benefits in preventing influenza-related hospitalizations and deaths in the elderly, particularly among those vaccinated in prior seasons. Efforts should therefore be made to improve vaccine uptake and the utilization of vaccines with greater effectiveness in the oldest elderly (e.g. high-dose and adjuvanted cell-based vaccines).

Influenza Vaccine Effectiveness in Inpatient and Outpatient Settings in the United States, 2015-2018.

Demonstration of influenza vaccine effectiveness (VE) against hospitalized illness in addition to milder outpatient illness may strengthen vaccination messaging. Our objective was to compare patient characteristics and VE between United States (US) inpatient and outpatient VE networks. We tested adults with acute respiratory illness (ARI) for influenza within 1 outpatient-based and 1 hospital-based VE network from 2015 through 2018. We compared age, sex, and high-risk conditions. The test-negative design was used to compare vaccination odds in influenza-positive cases vs influenza-negative controls. We estimated VE using logistic regression adjusting for site, age, sex, race/ethnicity, peak influenza activity, time to testing from, season (overall VE), and underlying conditions. VE differences (ΔVE) were assessed with 95% confidence intervals (CIs) determined through bootstrapping with significance defined as excluding the null. The networks enrolled 14 573 (4144 influenza-positive) outpatients and 6769 (1452 influenza-positive) inpatients. Inpatients were older (median, 62 years vs 49 years) and had more high-risk conditions (median, 4 vs 1). Overall VE across seasons was 31% (95% CI, 26%-37%) among outpatients and 36% (95% CI, 27%-44%) among inpatients. Strain-specific VE (95% CI) among outpatients vs inpatients was 37% (25%-47%) vs 53% (37%-64%) against H1N1pdm09; 19% (9%-27%) vs 23% (8%-35%) against H3N2; and 46% (38%-53%) vs 46% (31%-58%) against B viruses. ΔVE was not significant for any comparison across all sites. Inpatients and outpatients with ARI represent distinct populations. Despite comparatively poor health among inpatients, influenza vaccination was effective in preventing influenza-associated hospitalizations.

A Population-Based Propensity Score-Matched Study to Assess the Impact of Repeated Vaccination on Vaccine Effectiveness for Influenza-Associated Hospitalization Among the Elderly.

BackgroundInfluenza is a major cause of morbidity and mortality in the elderly worldwide. Influenza vaccination can prevent morbidity/mortality from influenza infection. A gap of 1–2 years, before an epidemic strain is recommended by the World Health Organization (WHO) to be the vaccine strain in Southeast Asia, has been reported; this results in a high rate of vaccine mismatch and excess influenza-associated morbidity. The aim of the current study was to evaluate the effect of repeated vaccination on vaccine effectiveness (VE) among the elderly in Taiwan, during years with and without early appearance of antigenically drifted strains.MethodsA historical cohort study was conducted to evaluate the impact of repeated vaccination on the reduction of influenza-associated hospitalization among persons older than 64 years over two influenza seasons: 2007–08, with all circulating virus strains mismatched, and 2008–09, with all virus strains matched with the vaccine strains, considering four exposure effects, namely current vaccine effect, sequential vaccination effect, residual protection effect and no vaccination effect. Propensity score matching on vaccination status was performed to ensure similar baseline characteristics between the groups that received and did not receive vaccination.ResultsOnly current-year vaccination in combination with prior history of annual revaccination significantly reduced the risk of hospitalization, with adjusted hazard ratios of 0.68 (95% CI: 0.54, 0.85) and 0.74 (95% CI: 0.57, 0.95) during the 2007–08 and 2008–09 influenza seasons, respectively. Further stratification showed that even during the 2007–08 influenza season, when all vaccinations were mismatched with the circulating strains, sequential vaccinations still significantly reduced influenza-associated hospitalization in the female population aged 68–74 and 75–84 years, with adjusted VE of 25.2% (95% CI: −9.6, 49.0%) and 36.9% (95% CI: 17.1, 52.0%), respectively.ConclusionOur study supports the recommendation of annual revaccination against influenza in the elderly, even though the circulating strain of influenza virus was antigenically mismatched with the vaccine strains.

Vaccine Effectiveness Against Influenza Hospitalization Among Children in the United States, 2015-2016.

Annual United States (US) estimates of influenza vaccine effectiveness (VE) in children typically measure protection against outpatient medically attended influenza illness, with limited data evaluating VE against influenza hospitalizations. We estimated VE for preventing laboratory-confirmed influenza hospitalization among US children. We included children aged 6 months-17 years with acute respiratory illness enrolled in the New Vaccine Surveillance Network during the 2015-2016 influenza season. Documented influenza vaccination status was obtained from state immunization information systems, the electronic medical record, and/or provider records. Midturbinate nasal and throat swabs were tested for influenza using molecular assays. We estimated VE as 100% × (1 - odds ratio), comparing the odds of vaccination among subjects testing influenza positive with subjects testing negative, using multivariable logistic regression. Of 1653 participants, 36 of 707 (5%) of those fully vaccinated, 18 of 226 (8%) of those partially vaccinated, and 85 of 720 (12%) of unvaccinated children tested positive for influenza. Of those vaccinated, almost 90% were documented to have received inactivated vaccine. The majority (81%) of influenza cases were in children ≤ 8 years of age. Of the 139 influenza-positive cases, 42% were A(H1N1)pdm09, 42% were B viruses, and 14% were A(H3N2). Overall, adjusted VE for fully vaccinated children was 56% (95% confidence interval [CI], 34%-71%) against any influenza-associated hospitalization, 68% (95% CI, 36%-84%) for A(H1N1)pdm09, and 44% (95% CI, -1% to 69%) for B viruses. These findings demonstrate the importance of annual influenza vaccination in prevention of severe influenza disease and of reducing the number of children who remain unvaccinated or partially vaccinated against influenza.

Relative and Absolute Effectiveness of High-Dose and Standard-Dose Influenza Vaccine Against Influenza-Related Hospitalization Among Older Adults-United States, 2015-2017.

Seasonal influenza causes substantial morbidity and mortality in older adults. High-dose inactivated influenza vaccine (HD-IIV), with increased antigen content compared to standard-dose influenza vaccines (SD-IIV), is licensed for use in people aged ≥65 years. We sought to evaluate the effectiveness of HD-IIV and SD-IIV for prevention of influenza-associated hospitalizations. Hospitalized patients with acute respiratory illness were enrolled in an observational vaccine effectiveness study at 8 hospitals in the United States Hospitalized Adult Influenza Vaccine Effectiveness Network during the 2015-2016 and 2016-2017 influenza seasons. Enrolled patients were tested for influenza, and receipt of influenza vaccine by type was recorded. Effectiveness of SD-IIV and HD-IIV was estimated using a test-negative design (comparing odds of influenza among vaccinated and unvaccinated patients). Relative effectiveness of SD-IIV and HD-IIV was estimated using logistic regression. Among 1487 enrolled patients aged ≥65 years, 1107 (74%) were vaccinated; 622 (56%) received HD-IIV, and 485 (44%) received SD-IIV. Overall, 277 (19%) tested positive for influenza, including 98 (16%) who received HD-IIV, 87 (18%) who received SD-IIV, and 92 (24%) who were unvaccinated. After adjusting for confounding variables, effectiveness of SD-IIV was 6% (95% confidence interval [CI] -42%, 38%) and that of HD-IIV was 32% (95% CI -3%, 54%), for a relative effectiveness of HD-IIV versus SD-IIV of 27% (95% CI -1%, 48%). During 2 US influenza seasons, vaccine effectiveness was low to moderate for prevention of influenza hospitalization among adults aged ≥65 years. High-dose vaccine offered greater effectiveness. None of these findings were statistically significant.

A severe influenza season in Austria and its impact on the paediatric population: mortality and hospital admission rates, november 2017 - march 2018

BackgroundIn Austria paediatric influenza-associated hospitalisations and deaths have never been systematically monitored. We examined the influenza season 2017/18 in terms of hospitalisation and mortality in the Austrian paediatric population and put the results into perspective of the available data from the last 15 years.MethodsCases of influenza-associated hospitalisations and deaths for season 2017/18 in children below 18 years were retrospectively collected from 12 and 33 Austrian hospitals, respectively. Hospitalisation and mortality rates for the whole Austrian paediatric population were estimated, adjusting for the population in each catchment area. Two Austrian databases were queried for hospitalisations and deaths associated with influenza during 2002–2016. Rough estimate of the vaccination coverage was calculated from a survey on 100 inpatients.ResultsInfluenza-related paediatric hospitalisation rate in season 2017/18 was estimated as 128 (CI: 122–135) per 100,000 children, much higher than the national average of 40 per 100,000 over the years 2002–2016. There were nine reported influenza-associated deaths among children, resulting in mortality rate of 0.67 (CI: 0.32–1.21) per 100,000 children.ConclusionsReported influenza-associated hospitalisations and fatalities demonstrate a high burden of influenza in the Austrian paediatric population corresponding with very low vaccination coverage.

Effects of Influenza Vaccination in the United States During the 2018-2019 Influenza Season.

Multivalent influenza vaccine products provide protection against influenza A(H1N1)pdm09, A(H3N2), and B lineage viruses. The 2018-2019 influenza season in the United States included prolonged circulation of A(H1N1)pdm09 viruses well-matched to the vaccine strain and A(H3N2) viruses, the majority of which were mismatched to the vaccine. We estimated the number of vaccine-prevented influenza-associated illnesses, medical visits, hospitalizations, and deaths for the season. We used a mathematical model and Monte Carlo algorithm to estimate numbers and 95% uncertainty intervals (UIs) of influenza-associated outcomes prevented by vaccination in the United States. The model incorporated age-specific estimates of national 2018-2019 influenza vaccine coverage, influenza virus-specific vaccine effectiveness from the US Influenza Vaccine Effectiveness Network, and disease burden estimated from population-based rates of influenza-associated hospitalizations through the Influenza Hospitalization Surveillance Network. Influenza vaccination prevented an estimated 4.4 million (95%UI, 3.4 million-7.1 million) illnesses, 2.3 million (95%UI, 1.8 million-3.8 million) medical visits, 58 000 (95%UI, 30 000-156 000) hospitalizations, and 3500 (95%UI, 1000-13 000) deaths due to influenza viruses during the US 2018-2019 influenza season. Vaccination prevented 14% of projected hospitalizations associated with A(H1N1)pdm09 overall and 43% among children aged 6 months-4 years. Influenza vaccination averted substantial influenza-associated disease including hospitalizations and deaths in the United States, primarily due to effectiveness against A(H1N1)pdm09. Our findings underscore the value of influenza vaccination, highlighting that vaccines measurably decrease illness and associated healthcare utilization even in a season in which a vaccine component does not match to a circulating virus.

521: Influenza-associated hospital admissions and ICU-level interventions during pregnancy

521: Influenza-associated hospital admissions and ICU-level interventions during pregnancy

Risk of Severe Influenza Among Adults With Chronic Medical Conditions.

Severe influenza illness is presumed more common in adults with chronic medical conditions (CMCs), but evidence is sparse and often combined into broad CMC categories. Residents (aged 18-80 years) of Central and South Auckland hospitalized for World Health Organization-defined severe acute respiratory illness (SARI) (2012-2015) underwent influenza virus polymerase chain reaction testing. The CMC statuses for Auckland residents were modeled using hospitalization International Classification of Diseases, Tenth Revision codes, pharmaceutical claims, and laboratory results. Population-level influenza rates in adults with congestive heart failure (CHF), coronary artery disease (CAD), cerebrovascular accidents (CVA), chronic obstructive pulmonary disease (COPD), asthma, diabetes mellitus (DM), and end-stage renal disease (ESRD) were calculated by Poisson regression stratified by age and adjusted for ethnicity. Among 891 276 adults, 2435 influenza-associated SARI hospitalizations occurred. Rates were significantly higher in those with CMCs compared with those without the respective CMC, except for older adults with DM or those aged <65 years with CVA. The largest effects occurred with CHF (incidence rate ratio [IRR] range, 4.84-13.4 across age strata), ESRD (IRR range, 3.30-9.02), CAD (IRR range, 2.77-10.7), and COPD (IRR range, 5.89-8.78) and tapered with age. Our findings support the increased risk of severe, laboratory-confirmed influenza disease among adults with specific CMCs compared with those without these conditions.

Influenza vaccine effectiveness against hospitalizations in children and older adults—Data from South America, 2013–2017. A test negative design

BackgroundIn 2013, the Pan American Health Organization established a multi-site, multi-country network to evaluate influenza vaccine effectiveness (VE). We pooled data from five consecutive seasons in five countries to conduct an analysis of southern hemisphere VE against laboratory-confirmed influenza hospitalizations in young children and older adults. MethodsWe used a test-negative design to estimate VE against laboratory-confirmed influenza in hospitalized young children (aged 6─24 months) and older adults (aged ≥60 years) in Argentina, Brazil, Chile, Colombia, and Paraguay. Following country-specific influenza surveillance protocol, hospitalized persons with severe acute respiratory infections (SARI) at 48 sentinel hospitals (March 2013–December 2017) were tested for influenza virus infection by rRT-PCR. VE was estimated for young children and older adults using logistic random effects models accounting for cluster (country), adjusting for sex, age (months for children, and age-in-year categories for adults), calendar year, country, preexisting conditions, month of illness onset and prior vaccination as an effect modifier for the analysis in adults. ResultsWe included 8426 SARI cases (2389 children and 6037 adults) in the VE analyses. Among young children, VE against SARI hospitalization associated with any influenza virus was 43% (95%CI: 33%, 51%) for children who received two doses, but was 20% (95%CI: −16%, 45%) and not statistically significant for those who received one dose in a given season. Among older adults, overall VE against SARI hospitalization associated with any influenza virus was 41% (95%CI: 28%, 52%), 45% (95%CI: 34%, 53%) against A(H3N2), 40% (95%CI: 18%, 56%) against A(H1N1)pdm09, and 20% (95%CI: −40%, 54%) against influenza B viruses. ConclusionsOur results suggest that over the five-year study period, influenza vaccination programs in five South American countries prevented more than one-third of laboratory confirmed influenza-associated hospitalizations in young children receiving the recommended two doses and vaccinated older adults.

Hospitalizations Associated with Respiratory Syncytial Virus and Influenza in Children, Including Children Diagnosed with Asthma.

There is uncertainty about the burden of hospitalization associated with respiratory syncytial virus (RSV) and influenza in children, including those with underlying medical conditions. We applied previously developed methodology to Health Care Cost and Utilization Project hospitalization data and additional data related to asthma diagnosis/previous history in hospitalized children to estimate RSV and influenza-associated hospitalization rates in different subpopulations of US children between 2003 and 2010. The estimated average annual rates (per 100,000 children) of RSV-associated hospitalization with a respiratory cause (ICD-9 codes 460-519) present anywhere in the discharge diagnosis were 2,381 (95% CI(2252,2515)) in children <1 year of age; 710.6 (609.1, 809.2) (1 y old); 395 (327.7, 462.4) (2 y old); 211.3 (154.6, 266.8) (3 y old); 111.1 (62.4, 160.1) (4 y old); 72.3 (29.3, 116.4) (5-6 y of age); 35.6 (9.9,62.2) (7-11 y of age); and 39 (17.5, 60.6) (12-17 y of age). The corresponding rates of influenza-associated hospitalization were lower, ranging from 181 (142.5, 220.3) in <1 year old to 17.9 (11.7, 24.2) in 12-17 years of age. The relative risks for RSV-related hospitalization associated with a prior diagnosis of asthma in age groups <5 y ranged between 3.1 (2.1, 4.7) (<1 y old) and 6.7 (4.2, 11.8) (2 y old; the corresponding risks for influenza-related hospitalization ranged from 2.8 (2.1, 4) (<1y old) to 4.9 (3.8, 6.4) (3 y old). RSV-associated hospitalization rates in young children are high and decline rapidly with age. There are additional risks for both RSV and influenza hospitalization associated with a prior diagnosis of asthma, with the rates of RSV-related hospitalization in the youngest children diagnosed with asthma being particularly high.

2329. Incidences and Characteristics of Influenza Among Pregnant Women in Middle-Income Countries: Preliminary Results of the Pregnancy and Influenza Multinational Epidemiologic (PRIME) Study

BackgroundThe World Health Organization recommends influenza vaccination for pregnant women. However, few data exist on influenza incidence and clinical course among pregnant women in middle-income countries where influenza vaccine use during pregnancy is often limited. We conducted a prospective cohort study of pregnant women to estimate incidences of influenza in Lima, Peru; Bangkok, Thailand; and Nagpur, India.MethodsPrior to and early in the 2017 and 2018 influenza seasons, we enrolled pregnant women aged > 18 years with expected delivery dates > 8 weeks after the start of the season. We contacted women twice weekly until end of pregnancy to identify illnesses with myalgia, cough, runny nose, sore throat, or difficulty breathing and collected nasal swabs from symptomatic women for influenza real-time reverse transcription polymerase chain reaction testing. Using 2017 cohort data, we calculated crude incidences per 10,000 pregnancy-months during influenza season by site and trimester and overall incidence weighted for population of women of childbearing age in each country.ResultsWe enrolled 4774 women with a median age of 26 years (interquartile range [IQR] 23–31) and gestational age of 20 weeks (IQR 15–24); 15% received influenza vaccine. Local influenza seasons spanned 4.5–8 months. Overall, 143 participants (3%) had influenza (113 (79%) influenza A and 30 (21%) influenza B). Weighted influenza incidence was 88.7/10,000 pregnancy-months (95% CI 68.6–114.8), though incidences varied up to two-fold by site (Figure 1). Incidences did not differ by pregnancy trimester (Figure 2). Among the 143 influenza episodes, the median duration was 7 days (IQR 5–10), 30% involved fever or chills, 43% disrupted daily activities, 47% prompted medical attention, 4% were associated with hospitalization, and < 1% were treated with antiviral medications.ConclusionOverall, pregnant women had an average risk of influenza of 0.9% per month of pregnancy spent in the influenza season with almost half of illnesses disrupting daily activities and prompting medical attention. Influenza-associated hospitalization was infrequent. These findings provide valuable inputs to estimate illnesses averted by vaccine programs and evaluate their cost–benefit among pregnant women in middle-income countries. Disclosures All authors: No reported disclosures.

2631. Influenza-Associated Intensive Care Unit Hospitalizations and Deaths in Children, During 2010–2019 in Greece

BackgroundThe clinico-epidemiological characteristics of children with severe influenza-related intensive care unit (ICU) admissions in Greece during 2010–2019 are described.MethodsAll laboratory-confirmed influenza cases (real-time PCR), in children 0–16 years old, admitted to Pediatric ICUs throughout the country, are reported using a mandatory notification system to the National Public Health Organization of Greece. Case fatality rates (CFR) were analyzed according to age and presence of comorbidities.ResultsFrom October 2010 to April 2019, 131 influenza cases [7.2/100,000 children, 65 (49.6%) girls] with PICUs admissions were recorded. The majority of cases (n = 78; 60%) occurred in the age group 0–4 years-old [31 (24%) children were < 12 months-old]. Sixty-five (49.6%) children had underlying comorbidities (22 neurological disease, 12 congenital syndromes, 7 cancer, 5 chronic respiratory, 19 other). The most common diagnosis was febrile ARDS and 67 (51.14%) had severe pneumonia (40% viral, 7% bacterial). Seventy-five (57.2%) children required invasive ventilation. Influenza A accounted for 102 (77.86%) of cases; out of 86 (84.31%) subtyped, 68 (79%) were AH1N1pdm09, and 18 (21%) were AH3N2. Influenza B accounted for 29 (22.13%) of cases. All children received oseltamivir. Median length of stay was 10 days (range 1–90). A total of 32 deaths was recorded (CFR 24.4%, total rate: 1.76/100,000 children); 13 (40.1%) deaths occurred in children with no known co-morbidity. Mortality rates were higher in children aged > 4 years (18/53, 33.9% vs. 14/78, 17.9%, P = 0.04) while there was a trend for children with comorbidities (19/65, 29.2% vs. 13/66, 19.69%, P = 0.1). Only 4% of children were previously immunized against influenza.ConclusionAH1N1pdm09 accounted for the vast majority of severe cases and influenza associated deaths in children in Greece over the last 10 years. Severe disease occurred also in children with no comorbitidies. Longitudinal clinico-epidemiological data should be considered in shaping the national immunization program.Disclosures All authors: No reported disclosures.

1615. Influenza Outbreaks in Long-Term Care Facilities, 2017–2018 Influenza Season, Dallas, Texas

BackgroundHigh rates of influenza-related hospitalizations and deaths occurred in the United States during the 2017–2018 influenza season. A record number of influenza outbreaks were reported in long-term care facilities (LTCF) in Dallas County. Public health surveillance of influenza-related intensive care unit (ICU) admissions and deaths in acute care hospitals improved early identification of outbreaks in LTCFs.MethodsA confirmed LTCF influenza outbreak was defined as at least 1 lab-confirmed influenza case plus at least 1 case of influenza-like illness among residents or staff within 72 hours. Outbreaks were self-reported by facilities or identified by the health department during investigations of ICU hospitalizations and deaths. CDC guidance for influenza outbreak management was provided and daily active surveillance was continued for at least 1 week after the last case was identified. Data collected included: numbers of ill residents and staff, vaccination rates, dates of illness and chemoprophylaxis initiation, hospitalizations and deaths. Fisher exact tests and Chi-square were performed using SAS 9.4.ResultsDuring this influenza season, 32 confirmed influenza outbreaks were identified in Dallas County LTCFs: 17 in skilled nursing facilities (SNF), 13 in assisted-living facilities (ALF) and 2 in hybrid SNF/ALF. The average attack rate in residents was 9.8% (range: 1–35%). Influenza hospitalization rates were higher in ALF compared with SNF outbreaks (OR: 2.2). Influenza-associated mortality rates were higher in ALF compared with SNF (OR: 3.1). Of the 32 outbreaks, 20 (63%) were self-reported by facilities to public health and 12 (38%) were identified through health department review of influenza-associated ICU hospitalizations. Facilities where outbreak cases were identified through public health surveillance of ICU admissions had significantly lower overall attack rates (5.9% vs. 12.1%, P = 0.01) and shorter time to initiation of facility-wide chemoprophylaxis (0.4 vs. 2.4 days, P = 0.05).ConclusionActive surveillance of influenza-associated ICU admissions in acute-care hospitals facilitated the early identification of influenza outbreaks in LTCFs, which was associated with lower overall attack rates and shorter time to initiation of facility-wide chemoprophylaxis.Disclosures All authors: No reported disclosures.

2746. Effectiveness of Influenza Vaccine for Prevention of Influenza-associated Hospitalizations Among Immunocompromised Adults—2017–2018

BackgroundImmunocompromised (IC) individuals are at higher risk for severe complications of influenza. Little literature describes vaccine effectiveness (VE) in this population. We evaluated VE for prevention of influenza-associated hospitalization among IC adults.MethodsWe analyzed data from adults hospitalized with acute respiratory illness (ARI) during the 2017–2018 FLU season at 9 hospitals participating in the US Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) study. Details of disease severity, underlying health status, and vaccination status were obtained through enrollment interviews and medical records. Prior year clinical encounter diagnoses and enrollment interviews were used to define IC groups. IC groups were mutually exclusive. VE was evaluated with a test-negative case–control design using multivariate logistic regression with PCR-confirmed influenza as the outcome and vaccination status as the exposure, adjusting for age, race, and other factors, and stratifying by immunocompromising conditions.ResultsOf 3524 adults hospitalized with ARI, 1210 (34%) had an immunocompromising condition. Chronic steroid (n = 397), chemo/radiation therapy (n = 242), hematologic condition (n = 175), and organ transplant (n = 144) were most common. HIV (n = 45) and stem cell transplant (SCT) (n = 28) were least common. IC patients were more likely to be vaccinated than non-IC (60% vs. 55%, P = 0.002). Overall, vaccination reduced risk of influenza hospitalization by 36% (95% CI: 24,46). Among IC adults, VE was 9% (95% CI: −25,34). VE was 32% (95% CI: 5,51) for chemo/radiation therapy, 29% (95% CI: 6,47) for chronic steroids, 29% (95% CI: -6,52) for hematologic conditions, −1% (95% CI: −50,32) for organ transplant, −48% (95% CI: −190,25) for HIV, and −154% (95% CI = −458,−15) for SCT (Figure 1).ConclusionVaccination reduced risk of influenza hospitalization among adults with the most prevalent immunocompromising conditions in our cohort; however, it had little to no effect in other groups, such as in HIV and organ and stem cell transplant recipients. Results support using other preventative strategies in addition to vaccinating adults with immunocompromising conditions, such as vaccination of close contacts. Disclosures All authors: No reported disclosures.

Vital Signs: Burden and Prevention of Influenza and Pertussis Among Pregnant Women and Infants - United States.

IntroductionVaccinating pregnant women with influenza vaccine and tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis vaccine (Tdap) can reduce influenza and pertussis risk for themselves and their infants.MethodsSurveillance data were analyzed to ascertain influenza-associated hospitalization among pregnant women and infant hospitalization and death associated with influenza and pertussis. An Internet panel survey was conducted during March 27–April 8, 2019, among women aged 18–49 years who reported being pregnant any time since August 1, 2018. Influenza vaccination before or during pregnancy was assessed among respondents with known influenza vaccination status who were pregnant any time during October 2018–January 2019 (2,097). Tdap receipt during pregnancy was assessed among respondents with known Tdap status who reported a live birth by their survey date (817).ResultsFrom 2010–11 to 2017–18, pregnant women accounted for 24%–34% of influenza-associated hospitalizations per season among females aged 15–44 years. From 2010 to 2017, a total of 3,928 pertussis-related hospitalizations were reported among infants aged <2 months (annual range = 262–743). Maternal influenza and Tdap vaccination coverage rates reported as of April 2019 were 53.7% and 54.9%, respectively. Among women whose health care providers offered vaccination or provided referrals, 65.7% received influenza vaccine and 70.5% received Tdap. The most commonly reported reasons for nonvaccination were believing the vaccine is not effective (influenza; 17.6%) and not knowing that vaccination is needed during each pregnancy (Tdap; 37.9%), followed by safety concerns for the infant (influenza =15.9%; Tdap = 17.1%).Conclusions and Implications for Public Health PracticeMany pregnant women do not receive the vaccines recommended to protect themselves and their infants, even when vaccination is offered. CDC and provider organizations’ resources are available to help providers convey strong, specific recommendations for influenza and Tdap vaccination that are responsive to pregnant women’s concerns.

Influenza and tuberculosis co-infection: A systematic review.

IntroductionThere are limited data on risk of severe disease or outcomes in patients with influenza and pulmonary tuberculosis (PTB) co‐infection compared to those with single infection.MethodsWe conducted a systematic review of published literature on the interaction of influenza viruses and PTB. Studies were eligible for inclusion if they presented data on prevalence, disease association, presentation or severity of laboratory‐confirmed influenza among clinically diagnosed or laboratory‐confirmed PTB cases. We searched eight databases from inception until December 2018. Summary characteristics of each study were extracted, and a narrative summary was presented. Cohort or case‐control studies were assessed for potential bias using the Newcastle‐Ottawa scale.ResultsWe assessed 5154 abstracts, reviewed 146 manuscripts and included 19 studies fulfilling selection criteria (13 human and six animal). Of seven studies reporting on the possible effect of the underlying PTB disease in patients with influenza, three of four analytical studies reported no association with disease severity of influenza infection in those with PTB, whilst one study reported PTB as a risk factor for influenza‐associated hospitalization.An association between influenza infection and PTB disease was found in three of five analytical studies; whereas the two other studies reported a high frequency of PTB disease progression and complications among patients with seasonal influenza co‐infection.ConclusionHuman analytical studies of an association between co‐infection and severe influenza‐ or PTB‐associated disease or increased prevalence of influenza co‐infection in individuals' hospitalized for PTB were not conclusive. Data are limited from large, high‐quality, analytical epidemiological studies with laboratory‐confirmed endpoints.

Influenza Vaccine Effectiveness in Preventing Hospitalizations in Older Patients With Chronic Obstructive Pulmonary Disease.

Annual influenza immunization is recommended for people with chronic obstructive pulmonary disease (COPD) by all major COPD clinical practice guidelines. We sought to determine the seasonal influenza vaccine effectiveness (VE) against laboratory-confirmed influenza-associated hospitalizations among older adults with COPD. We conducted a test-negative study of influenza VE in community-dwelling older adults with COPD in Ontario, Canada using health administrative data and respiratory specimens collected from patients tested for influenza during the 2010-11 to 2015-16 influenza seasons. Influenza vaccination was ascertained from physician and pharmacist billing claims. Multivariable logistic regression was used to estimate the adjusted odds ratio of influenza vaccination in people with, compared to those without, laboratory-confirmed influenza. Receipt of seasonal influenza vaccine was associated with an adjusted 22% (95% confidence interval [CI], 15%-27%) reduction in laboratory-confirmed influenza-associated hospitalization. Adjustment for potential misclassification of vaccination status increased this to 43% (95% CI, 35%-52%). Vaccine effectiveness was not found to vary by patient- or influenza-related variables. During the studied influenza seasons, influenza vaccination was at least modestly effective in reducing laboratory-confirmed influenza-associated hospitalizations in people with COPD. The imperfect effectiveness emphasizes the need for better influenza vaccines and other preventive strategies.

Burden of influenza-associated respiratory hospitalizations in the Americas, 2010-2015.

BackgroundDespite having influenza vaccination policies and programs, countries in the Americas underutilize seasonal influenza vaccine, in part because of insufficient evidence about severe influenza burden. We aimed to estimate the annual burden of influenza-associated respiratory hospitalizations in the Americas.MethodsThirty-five countries in the Americas with national influenza surveillance were invited to provide monthly laboratory data and hospital discharges for respiratory illness (International Classification of Diseases 10th edition J codes 0–99) during 2010–2015. In three age-strata (<5, 5–64, and ≥65 years), we estimated the influenza-associated hospitalizations rate by multiplying the monthly number of respiratory hospitalizations by the monthly proportion of influenza-positive samples and dividing by the census population. We used random effects meta-analyses to pool age-group specific rates and extrapolated to countries that did not contribute data, using pooled rates stratified by age group and country characteristics found to be associated with rates.ResultsSixteen of 35 countries (46%) contributed primary data to the analyses, representing 79% of the America’s population. The average pooled rate of influenza-associated respiratory hospitalization was 90/100,000 population (95% confidence interval 61–132) among children aged <5 years, 21/100,000 population (13–32) among persons aged 5–64 years, and 141/100,000 population (95–211) among persons aged ≥65 years. We estimated the average annual number of influenza-associated respiratory hospitalizations in the Americas to be 772,000 (95% credible interval 716,000–829,000).ConclusionsInfluenza-associated respiratory hospitalizations impose a heavy burden on health systems in the Americas. Countries in the Americas should use this information to justify investments in seasonal influenza vaccination—especially among young children and the elderly.