Impact of influenza vaccination on seasonal mortality in the US elderly population

BACKGROUND: Observational studies report that influenza vaccination reduces winter mortality risk from any cause by 50% among the elderly. Influenza vaccination coverage among elderly persons (> or =65 years) in the United States increased from between 15% and 20% before 1980 to 65% in 2001. Unexpectedly, estimates of influenza-related mortality in this age group also increased during this period. We tried to reconcile these conflicting findings by adjusting excess mortality estimates for aging and increased circulation of influenza A(H3N2) viruses. METHODS: We used a cyclical regression model to generate seasonal estimates of national influenza-related mortality (excess mortality) among the elderly in both pneumonia and influenza and all-cause deaths for the 33 seasons from 1968 to 2001. We stratified the data by 5-year age group and separated seasons dominated by A(H3N2) viruses from other seasons. RESULTS: For people aged 65 to 74 years, excess mortality rates in A(H3N2)-dominated seasons fell between 1968 and the early 1980s but remained approximately constant thereafter. For persons 85 years or older, the mortality rate remained flat throughout. Excess mortality in A(H1N1) and B seasons did not change. All-cause excess mortality for persons 65 years or older never exceeded 10% of all winter deaths. CONCLUSIONS: We attribute the decline in influenza-related mortality among people aged 65 to 74 years in the decade after the 1968 pandemic to the acquisition of immunity to the emerging A(H3N2) virus. We could not correlate increasing vaccination coverage after 1980 with declining mortality rates in any age group. Because fewer than 10% of all winter deaths were attributable to influenza in any season, we conclude that observational studies substantially overestimate vaccination benefit.     

The impact of influenza epidemics on hospitalizations

The traditional method for assessing the severity of influenza seasons is to estimate the associated increase (i.e., excess) in pneumonia and influenza (P&I) mortality. In this study, excess P&I hospitalizations were estimated from National Hospital Discharge Survey Data from 26 influenza seasons (1970-1995). The average seasonal rate of excess P&I hospitalization was 49 (range, 8-102) /100,000 persons, but average rates were twice as high during A(H3N2) influenza seasons as during A(H1N1)/B seasons. Persons aged <65 years had 57% of all influenza-related hospitalizations; however, the average seasonal risk for influenza-related P&I hospitalizations was much higher in the elderly than in persons aged <65 years. The 26 pairs of excess P&I hospitalization and mortality rates were linearly correlated. During the A(H3N2) influenza seasons after the 1968 pandemic, excess P&I hospitalizations declined among persons aged <65 years but not among the elderly. This suggests that influenza-related hospitalizations will increase disproportionately among younger persons in future pandemics.     

Hospitalizations and deaths due to respiratory illnesses during influenza seasons: a comparison of community residents,senior housing residents,and nursing home residents

BACKGROUND: Although research indicates that influenza is a major cause of morbidity and mortality among older adults, few studies have tried to identify which seniors are particularly at risk of experiencing complications of influenza. The purpose of this study was to compare hospitalizations and deaths due to respiratory illnesses during influenza seasons among seniors (aged 65+) living in the community, senior residences (apartments reserved for seniors), and nursing homes. METHODS: Using administrative data, all hospital admissions and deaths due to respiratory illnesses (pneumonia and influenza, chronic lung disease, and acute respiratory diseases) were identified for all individuals aged 65 and older living in Winnipeg, Canada (approximately 88,000 individuals) during four influenza seasons (1995-1996 to 1998-1999). RESULTS: Hospitalization and death rates for respiratory illnesses increased significantly during influenza seasons, compared to fall periods (e.g., 42.7 vs 25.2 hospitalizations per 1000 population aged 80 and older). Moreover, hospitalization rates for pneumonia and influenza, chronic lung disease, and acute respiratory diseases were higher among individuals living in senior residences (42.5 per 1000 for all respiratory illnesses combined) than their counterparts living in the community (22.8 per 1000). Furthermore, deaths due to pneumonia and influenza and chronic lung disease were higher among senior housing residents (4.2 per 1000) than community residents (2.6 per 1000) and were particularly high among nursing home residents (52.1 per 1000). CONCLUSIONS: Individuals living in seniors residences are at increased risk of being hospitalized for and dying of respiratory illnesses during influenza seasons. Given that influenza vaccination is currently the best method to reduce influenza-associated illnesses among seniors, this suggests that influenza vaccination strategies should be targeted at this population.     

Influenza-related mortality among adults aged 25-54 years with AIDS in South Africa and the United States of america

Background.?Data are limited on human immunodeficiency virus (HIV)-associated influenza burden in sub-Saharan Africa and the impact of highly active antiretroviral therapy (HAART). We compared influenza-related mortality in adults with AIDS in South Africa and the United States in the pre-HAART era and evaluated mortality trends after HAART introduction in the United States. Methods.?Monthly all-cause and pneumonia and influenza (P&I) mortality rates were compiled for adults with AIDS aged 25-54 years in South Africa (1998-2005) and the United States (pre-HAART era, 1987-1994; HAART era, 1997-2005). We estimated influenza-related deaths as excess mortality above a model baseline during influenza epidemic periods. Influenza-related mortality rates in adults with AIDS were compared with rates for age peers in the general population and adults ≥65 years old. Results.?In the United States before HAART, influenza-related mortality rates in adults with AIDS were 150 (95% confidence interval [CI], 49-460) and 208 (95% CI, 74-583) times greater than in the general population for all-cause and P&I deaths, respectively, and 2.5 (95% CI, 0.9-7.2) and 4.1 (95% CI, 1.4-13) times higher than in elderly adults. After HAART introduction , influenza-related mortality in adults with AIDS dropped 3-6-fold but remained elevated compared with the general population (all-cause relative risk [RR], 44 [95% CI, 16-121]); P&I RR, 73 [95% CI, 47-113]). Influenza-related mortality in South African adults with AIDS in recent years was similar to that in the United States in the pre-HAART era. Conclusions.?Adults with AIDS experience substantially elevated influenza-associated mortality, which declines with widespread HAART introduction but does not disappear. These data support increased access to HAART and influenza vaccination for HIV-infected adults.     

Comparison of two vaccination programmes in preventing influenza-related hospitalization among the elderly during two consecutive seasons

The protective effect of influenza vaccine against influenza related hospitalization is well established at an individual level, but the effect of vaccination programme at the population level is unknown. In this study we compared a risk disease-based free-of-charge influenza vaccination programme in preventing hospitalizations due to influenza or pneumonia and cardiovascular diseases during 2 consecutive influenza seasons 1992/93 and 1993/94 in 43 municipalities in northern Finland. Vaccinations were carried out and reported by local staff in health centres. Data of hospital treatment periods were obtained from the National Hospital Discharge Register. During the influenza seasons the number of hospitalizations due to cardiovascular diseases and influenza/pneumonia increased by 13%. In the 1993/1994 season the increase in the study area with the risk disease-based vaccination programme was 22 per 1000 persons (95% CI 19-24), and with an age-based programme 3.3 per 1000 persons (95% CI 2.5-4.0), while the increase in the 1992/1993 season in both areas was 3-4 per 1000. The excess of hospitalization related to influenza epidemics is mostly due to cardiovascular diseases and varies from y to y, as do the benefits gained by vaccination.     

Relation between influenza vaccination and outpatient visits, hospitalization, and mortality in elderly persons with chronic lung disease

BACKGROUND: Influenza vaccine is underused in groups targeted for vaccination. OBJECTIVE: To define the effects of influenza and the benefits of influenza vaccination in elderly persons with chronic lung disease. DESIGN: Retrospective, multiseason cohort study. SETTING: Large managed care organization. PATIENTS: All elderly members of a managed care organization who had a previous diagnosis of chronic lung disease. MEASUREMENTS: Outcomes in vaccinated and unvaccinated persons for the 1993-1994, 1994-1995, and 1995-1996 influenza seasons were compared after adjustment for baseline demographic and health characteristics. All data were obtained from administrative databases. RESULTS: Vaccination rates were greater than 70% for each season. Among unvaccinated persons, hospitalization rates for pneumonia and influenza were twice as high in the influenza seasons as they were in the interim (noninfluenza) periods. Influenza vaccination was associated with fewer hospitalizations for pneumonia and influenza (adjusted risk ratio, 0.48 [95% CI, 0.28 to 0.82]) and with lower risk for death (adjusted odds ratio, 0.30 [CI, 0.21 to 0.43]) during the influenza seasons. It was also associated with fewer outpatient visits for pneumonia and influenza and for all respiratory conditions. CONCLUSIONS: For elderly persons with chronic lung disease, influenza is associated with significant adverse health effects and influenza vaccination is associated with substantial health benefits, including fewer outpatient visits, fewer hospitalizations, and fewer deaths. Health care providers should take advantage of all opportunities to immunize these high-risk patients.     

Mortality attributable to 9 common infections: significant effect of influenza a, respiratory syncytial virus, influenza B, norovirus, and parainfluenza in elderly persons

Background.Because there may be substantial hidden mortality caused by common seasonal pathogens, we estimated the number of deaths in elderly persons attributable to viruses and bacteria for which robust weekly laboratory surveillance data were available. Methods.On weekly time series (1999-2007) we used regression models to associate total death counts in individuals aged 65-74, 75-84, and ≥85 years (a population of 2.5 million) with pathogen circulation-influenza A (season-specific), influenza B, respiratory syncytial virus (RSV), parainfluenza, enterovirus, rotavirus, norovirus, Campylobacter, and Salmonella-adjusted for extreme outdoor temperatures. Results.Influenza A and RSV were significantly (P?相似文献   

Complications of viral influenza

Viral influenza is a seasonal infection associated with significant morbidity and mortality. In the United States more than 35,000 deaths and 200,000 hospitalizations due to influenza occur annually, and the number is increasing. Children aged less than 1 year and adults aged more than 65 years, pregnant woman, and people of any age with comorbid illnesses are at highest risk. Annual vaccination is the cornerstone of prevention, but some older patients may derive less benefit from immunization than otherwise fit individuals. If started promptly, antiviral medications may reduce complications of acute influenza, but increasing resistance to amantadine and perhaps neuraminidase inhibitors underscores the need for novel prevention and treatment strategies. Pulmonary complications of influenza are most common and include primary influenza and secondary bacterial infection. Either may cause pneumonia, and each has a unique clinical presentation and pathologic basis. Staphylococcus aureus, including methicillin-resistant strains, is an important cause of secondary bacterial pneumonia with high mortality. During influenza season, treatment of pneumonia should include empiric coverage for this pathogen. Neuromuscular and cardiac complications are unusual but may manifest in persons of any age.     

Influenza surveillance in an urban area

In Houston the yearly influenza epidemics have been defined virologically by community surveillance obtained by testing specimens submitted from patients with acute respiratory illnesses seen by sentinel physicians. Mortality attributed to influenza and pneumonia has increased regularly during the period of intense influenza virus activity, but the peak has lagged two weeks behind the peak of activity defined by the virological surveillance. Most of the deaths occurred in persons aged 65 years and older; the average annual rate has been 103.5 per 100,000 in that age group. Hospitalizations for pneumonia and other acute respiratory conditions also peaked during influenza epidemics; the highest rate occurred in the elderly, but children under five years of age also had high rates. Morbidity in the ambulatory setting was highest in children. The average visit rate for children under five years of age was 28%; the rate decreased to about 10% for persons aged 10 years and older. Improved coverage with more immunogenic vaccines is needed to protect the elderly. Young children would benefit from universal immunization with available live attenuated vaccines.     

Role of influenza and other respiratory viruses in admissions of adults to Canadian hospitals

Objective We sought to estimate age‐specific hospitalization rates attributed to influenza and other virus for adults. Methods Admissions from Canada’s national hospitalization database (Canadian Institute of Health Information), from 1994/95 to 1999/2000, were modeled as a function of proxy variables for influenza, respiratory syncytial virus (RSV) and other viral activity, seasonality and trend using a Poisson regression model and stratified by age group. Results The average annual influenza‐attributed hospitalization rate for all adults, 20 years of age or older, over the study period, which included three severe seasons, was an estimated 65/100 000 population (95% CI 63–67). Among persons aged 65 and over, 270–340 admissions per 100 000 population per year were attributed to influenza, while 30–110, 60–90 and 130–350 per 100 000 were attributed to RSV, parainfluenza (PIV) and other respiratory viruses, respectively. Although marked season‐to‐season variation in age‐specific hospitalization rates attributable to influenza was observed in persons 50 years of age and older, increasing risk with age was preserved at all time periods. Conclusions Influenza, RSV, PIV and other respiratory viruses were all associated with morbidity requiring hospitalization, while influenza was responsible for peak respiratory admissions. The burden of health care utilization associated with respiratory viruses is appreciable beginning in the sixth decade and increases significantly with age.     

Effect of influenza vaccination on disease progression among HIV-infected persons

OBJECTIVE: To describe the effect of influenza vaccination on long-term change in CD4 count and HIV RNA level, and on progression to AIDS or death. DESIGN AND SETTING: A longitudinal medical record review set in 113 medical clinics in 10 United States cities. PATIENTS: A total of 36,050 HIV-infected persons aged > or = 13 years in care for HIV infection. MAIN OUTCOME MEASURES: Change in CD4 count and HIV RNA level at follow-up (3-12 months after vaccination); hazard ratios (HR) for association of influenza vaccine with progression from baseline CD4 or HIV RNA level to AIDS and to death. RESULTS: The median CD4 count among all persons decreased 28 cells/year during follow-up, with no difference in change in CD4 count between the 8007 (40%) vaccinated (median = 6 months, vaccine to follow-up CD4 count) and the 11,794 unvaccinated persons. In a viral load subanalysis, median HIV RNA level decreased 90 copies/ml per year among all persons during follow-up; decreases were not different between vaccinated and unvaccinated persons (median = 7 months, vaccine to follow-up HIV RNA level determination). Influenza vaccination was weakly associated with decreased risk of progression to clinical AIDS [HR 0.93; 95% confidence interval (CI), 0.87-0.99], but not associated with time to death (HR, 0.97; CI, 0.93-1.01). CONCLUSIONS: No negative long-term effect of influenza vaccination on CD4 counts, HIV RNA levels, or progression to AIDS or death was found in this HIV-infected population. These data suggest that physicians should not withhold influenza vaccine because of concerns about long-term detrimental effects of increased viral replication.     

The health and economic benefits associated with pneumococcal vaccination of elderly persons with chronic lung disease

BACKGROUND: More than 50% of the elderly population has not received pneumococcal vaccination. Uncertainty regarding the benefits of immunization, particularly for noninvasive disease, may contribute to the underuse of pneumococcal vaccine. OBJECTIVE: To assess the health and economic benefits associated with pneumococcal vaccination. METHODS: We conducted a 2-year retrospective cohort study among all elderly members of a staff-model managed care organization who had a baseline diagnosis of chronic lung disease. The study outcomes were assessed over 2 years, from November 15, 1993, through November 14, 1995, and included hospitalizations for pneumonia and influenza, death, and hospitalization costs. Using administrative data, we compared these outcomes for vaccinated and unvaccinated subjects using multivariate models to control for subjects' baseline demographic and health characteristics. The additive benefits of combined influenza and pneumococcal vaccination were also assessed for the 2 influenza seasons included in the study. RESULTS: There were 1898 subjects. Pneumococcal vaccination was associated with significantly lower risks for pneumonia hospitalizations (adjusted risk ratio [RR], 0.57; 95% confidence interval [CI], 0.38-0.84; P=.005) and for death (adjusted RR, 0.71; 95% CI, 0.56-0.91; P = .008). For the control outcome of all nonpneumonia hospitalizations, rates did not differ significantly between the 2 groups (adjusted RR, 0.91; 95% CI, 0.77-1.07; P= .24). During the influenza seasons included in the study, the benefits of pneumococcal and influenza vaccinations were additive, with an adjusted RR of 0.28 (95% CI, 0.14-0.58; P<.001) for the number of hospitalizations for pneumonia and influenza among persons who had received both vaccinations compared with those who had received neither and an adjusted odds ratio of 0.18 (95% CI, 0.11-0.31; P<.001) for death. Over the 2-year outcome period, pneumococcal vaccination was also associated with direct medical care cost savings. CONCLUSIONS: Pneumococcal vaccination of elderly persons with chronic lung disease was associated with fewer hospitalizations for pneumonia, fewer deaths, and direct medical care cost savings.     

Clinical effectiveness of influenza vaccination in persons younger than 65 years with high-risk medical conditions: the PRISMA study

BACKGROUND: Influenza vaccination has consistently been shown to prevent all-cause death and hospitalizations during influenza epidemics among seniors. However, such benefits have not yet been demonstrated among younger individuals with high-risk medical conditions. In the present study, we evaluated the effectiveness of influenza vaccine in persons recommended for vaccination of any age during an epidemic. METHODS: We conducted a case-control study during the 1999-2000 influenza A epidemic nested in a cohort of 75,227 primary care patients. End points were all-cause mortality and episodes of hospitalizations or general practitioner (GP) visits for influenza, pneumonia, other acute respiratory disease, acute otitis media, myocardial infarction, heart failure, and stroke. The effectiveness of vaccination was evaluated by means of logistic regression analysis with adjustments for age, sex, prior health care use, medication use, and comorbid conditions. RESULTS: Among high-risk children and adolescents younger than 18 years (n=5933; 8% of the study population), 1 death, 3 hospitalizations for pneumonia, and 160 GP visits occurred. After adjustments, 43% (95% confidence interval [CI], 10%-64%) of visits were prevented. Among high-risk adults aged between 18 and 64 years (n=24 928; 33% of the study population), 47 deaths, 23 hospitalizations, and 363 GP visits occurred. After adjustments, vaccination prevented 78% of deaths (95% CI, 39%-92%), 87% of hospitalizations (95% CI, 39%-97%), and 26% of GP visits (95% CI, 7%-47%). Among elderly persons (n=44 366; 59% of the study population), 272 deaths and 166 hospitalizations occurred, and after adjustments the vaccine prevented these end points by 50% (95% CI, 23%-68%) and 48% (95% CI, 7%-71%), respectively. CONCLUSION: Persons with high-risk medical conditions of any age can substantially benefit from annual influenza vaccination during an epidemic.     

Estimates of mortality attributable to influenza and RSV in the United States during 1997–2009 by influenza type or subtype,age, cause of death,and risk status

Background

Influenza and respiratory syncytial virus (RSV) cause substantial mortality from respiratory and other causes in the USA, especially among people aged 65 and older.

Objectives

We estimated the influenza-attributable mortality and RSV-attributable mortality in the USA, stratified by age and risk status, using outcome definitions with different sensitivity and specificity.

Methods

Influenza- and RSV-associated mortality was assessed from October 1997–March 2009 using multiple linear regression modeling on data obtained from designated government repositories.

Results

The main outcomes and measures included mortality outcome definitions—pneumonia and influenza, respiratory broad, and cardiorespiratory disease. A seasonal average of 10 682 (2287–16 363), 19 100 (4862–29 245), and 28 169 (6797–42 316) deaths was attributed to influenza for pneumonia and influenza, respiratory broad, and cardiorespiratory outcome definitions, respectively. Corresponding values for RSV were 6211 (4584–8169), 11 300 (8546–14 244), and 17 199 (13 384–21 891), respectively. A/H3N2 accounted for seasonal average of 71% influenza-attributable deaths; influenza B accounted for most (51–95%) deaths during four seasons. Approximately 70% influenza-attributable deaths occurred in individuals ≥75 years, with increasing mortality for influenza A/H3N2 and B, but not A/H1N1. In children aged 0–4 years, an average of 97 deaths was attributed to influenza (A/H3N2 = 49, B = 33, A/H1N1 = 15) and 165 to respiratory broad outcome definition (RSV). Influenza-attributable mortality was 2·94-fold higher in high-risk individuals.

Conclusions

Influenza-attributable mortality was highest in older and high-risk individuals and mortality in children was higher than reported in passive Centers for Disease Control and Prevention surveillance. Influenza B-attributable mortality was higher than A in four of 12 seasons. Our estimates represent an updated assessment of influenza-attributable mortality in the USA.     

Where adults reported receiving influenza vaccination in the United States

BACKGROUND: Influenza vaccination coverage remains unacceptably low among persons aged > or =65 years and younger high-risk adults. This study assessed locations at which US adults receive influenza (flu) vaccinations and the relative roles that traditional and nontraditional vaccination settings play in influenza vaccine delivery. METHODS: We analyzed data on types of settings at which last flu shot was received, reported by adult respondents to the 1999 Behavioral Risk Factor Surveillance System, stratified by age group and medical condition. We used multivariable logistic regression to identify factors associated with nontraditional vaccination settings. RESULTS: In 1998-1999, reported influenza vaccination coverage was 19% for persons aged 18-49 years, 36% for persons aged 50-64 years, and 67% for persons aged > or =65 years. Seventy percent of flu shots received by persons aged > or =18 years were reportedly administered in doctors' offices and other traditional settings. Vaccination in nontraditional settings (eg, workplace, stores, community centers) was more likely for young, healthy, employed, white, college-educated adults who had not had a recent routine checkup. CONCLUSION: Physicians should offer vaccination services at every opportunity. Increasing access to vaccination services in nontraditional settings should be considered as another strategy in pursuit of national vaccination coverage objectives.     

Influenza‐associated mortality in Thailand, 2006–2011

Background

Influenza-associated mortality in subtropical or tropical regions, particularly in developing countries, remains poorly quantified and often underestimated. We analyzed data in Thailand, a middle-income tropical country with good vital statistics and influenza surveillance data.

Methods

We obtained weekly mortality data for all-cause and three underlying causes of death (circulatory and respiratory diseases, and pneumonia and influenza), and weekly influenza virus data, from 2006 to 2011. A negative binomial regression model was used to estimate deaths attributable to influenza in two age groups (<65 and ≥65 years) by incorporating influenza viral data as covariates in the model.

Results

From 2006 to 2011, the average annual influenza-associated mortality per 100 000 persons was 4·0 (95% CI: −18 to 26). Eighty-three percent of influenza-associated deaths occurred among persons aged > 65 years. The average annual rate of influenza-associated deaths was 0·7 (95% CI: −8·2 to 10) per 100 000 population for person aged <65 years and 42 (95% CI: −137 to 216) for person aged ≥ 65 years.

Discussion

In Thailand, estimated excess mortality associated with influenza was considerable even during non-pandemic years. These data provide support for Thailand''s seasonal influenza vaccination campaign. Continued monitoring of mortality data is important to assess impact.     

Effects of antiretroviral therapy and opportunistic illness primary chemoprophylaxis on survival after AIDS diagnosis. Adult/Adolescent Spectrum of Disease Group.

OBJECTIVE: To examine the effects of antiretroviral therapy (ART) and opportunistic illness chemoprophylaxis on the survival of persons with AIDS and survival time based on year of AIDS diagnosis. DESIGN: Longitudinal medical record review. SETTING: Ninety-three hospitals and clinics in nine cities in the USA. PATIENTS: We observed 19,565 persons with AIDS from 1990 through January 1998. INTERVENTIONS: Prescribed use of antiretroviral monotherapy, dual- and triple-combination therapies, primary prophylaxis against Pneumocystis carinii pneumonia and Mycobacterium avium complex, and pneumococcal vaccine. MAIN OUTCOME MEASURES: Time from AIDS diagnosis to death in the presence and absence of ART. Survival curves were compared of AIDS cases diagnosed during 1990-1992 and 1993-1995. RESULTS: Triple ART had the greatest effect on the risk of death [relative risk (RR), 0.15; 95% confidence limit (CL), 0.12, 0.17], followed by dual ART (RR, 0.24; 95% CL, 0.22, 0.26), and monotherapy (RR, 0.38; 95% CL, 0.36, 0.40). Risk of death was decreased among persons receiving Pneumocystis carinii pneumonia prophylaxis (RR, 0.79; 95% CL, 0.70, 0.89) and Mycobacterium avium complex prophylaxis (RR, 0.76; 95% CL, 0.68, 0.86). Median survival increased from 31 months [95% confidence interval (CI), 30-32 months] for AIDS cases diagnosed during 1990-1992 to 35 months (95% CI, 35-38 months) for cases diagnosed during 1993-1995. CONCLUSIONS: The risk of death was decreased for persons receiving triple ART compared with persons receiving dual therapy and persons receiving monotherapy. Increased use of ART and improved ART regimens probably contributed to prolonged survival of persons whose diagnosis was made during 1993-1995 compared with persons whose diagnosis was made during 1990-1992.     

Influenza vaccine effectiveness in preventing hospitalizations and deaths in persons 65 years or older in Minnesota, New York, and Oregon: data from 3 health plans

This study developed methods and determined the impact of influenza vaccination on elderly persons in 3 large health plans: Kaiser Permanente Northwest, HealthPartners, and Oxford Health Plans. Data for the 1996-1997 and 1997-1998 seasons were extracted from administrative databases. Subjects were health plan members > or = 65 years old. Comorbid conditions collected from the preceding year were used for risk adjustment with logistic regression. The virus-vaccine match was excellent for year 1 and fair for year 2. Both years, during peak and total periods, vaccination reduced all causes of death and hospitalization for pneumonia and influenza: hospitalizations were reduced by 19%-20% and 18%-24% for years 1 and 2, respectively, and deaths were reduced by 60%-61% and 35%-39% for the same periods. These results show that all elderly persons should be immunized annually for influenza. The methods used in this study are an efficient cost-effective way to study vaccine impact and similar questions.     

Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity

Please cite this paper as: Jhung et al. (2011) Preliminary results of 2009 pandemic influenza surveillance in the United States using the Aggregate Hospitalization and Death Reporting Activity. Influenza and Other Respiratory Viruses 5(5), 321–327. Background To augment established influenza surveillance systems in the United States, the Centers for Disease Control and Prevention and the Council of State and Territorial Epidemiologists implemented the Aggregate Hospitalization and Death Reporting Activity (AHDRA) in August 2009. The AHDRA was designed to meet increased demands for timely and detailed information describing illness severity during the 2009 H1N1 influenza A (pH1N1) pandemic response. Objectives We describe the implementation of AHDRA and provide preliminary results from this new surveillance activity. Methods All 50 US states were asked to report influenza‐associated hospitalizations and deaths to AHDRA each week using either a laboratory‐confirmed or syndromic surveillance definition. Aggregate counts were used to calculate age‐specific weekly and cumulative rates per 100 000, and laboratory‐confirmed reports were used to estimate the age distribution of pH1N1 influenza‐associated hospitalizations and deaths. Results From August 30, 2009, through April 6, 2010, AHDRA identified 41 689 laboratory‐confirmed influenza‐associated hospitalizations and 2096 laboratory‐confirmed influenza‐associated deaths. Aggregate Hospitalization and Death Reporting Activity rates peaked earlier than hospitalization and death rates seen in previous influenza seasons with other surveillance systems, and the age distribution of cases revealed a tendency for hospitalizations and deaths to occur in persons <65 years for age. Conclusions Aggregate Hospitalization and Death Reporting Activity laboratory‐confirmed reports provided important information during the 2009 pandemic response. Aggregate Hospitalization and Death Reporting Activity syndromic reports were marked by low representativeness and specificity and were therefore less useful. The AHDRA was implemented quickly and may be a useful surveillance system to monitor severe illness during future influenza pandemics.