Kristin L Nichol

Publications of Kristin L Nichol

• Agreement between Internet-Based Self- and Proxy-Reported Health Care Resource Utilization and Administrative Health Care Claims.

  Authors: Liisa Palmer, Stephen S Johnston, Matthew D Rousculp, Bong-Chul Chu, Kristin L Nichol, Parthiv J Mahadevia

  Value in health : the journal of the International Society for Pharmacoeconomics and Outcomes Research. 05/2012; 15(3):458-65.

  Although Internet-based surveys are becoming more common, little is known about agreement between administrative claims data and Internet-based survey self- and proxy-reported health care resourceAlthough Internet-based surveys are becoming more common, little is known about agreement between administrative claims data and Internet-based survey self- and proxy-reported health care resource utilization (HCRU) data. This analysis evaluated the level of agreement between self- and proxy-reported HCRU data, as recorded through an Internet-based survey, and administrative claims-based HCRU data. The Child and Household Influenza-Illness and Employee Function study collected self- and proxy-reported HCRU data monthly between November 2007 and May 2008. Data included the occurrence and number of visits to hospitals, emergency departments, urgent care centers, and outpatient offices for a respondent's and his or her household members' care. Administrative claims data from the MarketScan® Databases were assessed during the same time and evaluated relative to survey-based metrics. Only data for individuals with employer-sponsored health care coverage linkable to claims were included. The Kappa (κ) statistic was used to evaluate visit concordance, and the intraclass correlation coefficient was used to describe frequency consistency. Agreement for presence of a health care visit and the number of visits were similar for self- and proxy-reported HCRU data. There was moderate to substantial agreement related to health care visit occurrence between survey-based and claims-based HCRU data for inpatient, emergency department, and office visits (κ: 0.47-0.77). There was less agreement on health care visit frequencies, with intraclass correlation coefficient values ranging from 0.14 to 0.71. This study's agreement values suggest that Internet-based surveys are an effective method to collect self- and proxy-reported HCRU data. These results should increase confidence in the use of the Internet for evaluating disease burden.

• Cost-effectiveness and socio-economic aspects of childhood influenza vaccination.

  Authors: Kristin L Nichol

  Vaccine. 08/2011; 29(43):7554-8.

  Children have high rates of healthcare utilization due to influenza. In addition, children also transmit influenza to others in their households and the community. The costs of influenza in childrenChildren have high rates of healthcare utilization due to influenza. In addition, children also transmit influenza to others in their households and the community. The costs of influenza in children include the direct medical care costs from increased outpatient visits and hospitalizations, and also indirect costs due to productivity losses especially for their parents and due to transmission of the virus to others. A variety of studies using different methods and assumptions have assessed the cost-effectiveness of influenza vaccination of children, and many find that vaccination is either cost saving or cost effective.

• Telephone survey assessment of household patterns of influenza vaccination, Twin Cities seven county metro area, 2008-2009.

  Authors: Mark A Robien, Alan R Lifson, Sue Duval, Kristin L Nichol, Patricia Ferrieri

  Vaccine. 03/2011; 29(23):4033-42.

  Major national surveys do not collect the influenza vaccination status of all household members, thus limiting current understanding of household influenza vaccination patterns. In an early 2009Major national surveys do not collect the influenza vaccination status of all household members, thus limiting current understanding of household influenza vaccination patterns. In an early 2009 telephone survey of 800 households in the metropolitan Minneapolis-St Paul area, household respondents reported the age, gender, and 2008-2009 seasonal influenza vaccination status of all household members. After poststratification to adjust for nonresponse, the full household influenza vaccination rate for multiperson households is 35.2%, partial household influenza vaccination rate is 39.9% and the rate of complete household nonvaccination is 24.9%. Full household influenza vaccination is more common in households with an elderly resident, intermediate in households with a child under 5 years of age, and less common in the remaining households. No household members are vaccinated in approximately 10% of multiperson households with either an elderly adult or young child; the corresponding rate in other households is 32.8%. An estimated 51.4% of households with children over 1 year of age have all children vaccinated against influenza; 43.5% of households with children had no children vaccinated against influenza. Households with younger children are more likely to have all children vaccinated and less likely to have no children vaccinated. We believe this is the first study to describe the prevalence of household influenza vaccination patterns. Continued efforts to monitor and increase household vaccination may be a valuable strategy to protect individuals and communities from influenza.

• Attending work while sick: implication of flexible sick leave policies.

  Authors: Matthew D Rousculp, Stephen S Johnston, Liisa A Palmer, Bong-Chul Chu, Parthiv J Mahadevia, Kristin L Nichol

  Journal of occupational and environmental medicine / American College of Occupational and Environmental Medicine. 09/2010; 52(10):1009-13.

  To examine the impact of various flexible sick leave policies (FSLPs) on workplace attendance of employees with self-reported "severe" influenza-like-illness (ILI) symptoms. This is a prospectiveTo examine the impact of various flexible sick leave policies (FSLPs) on workplace attendance of employees with self-reported "severe" influenza-like-illness (ILI) symptoms. This is a prospective study of employees from three US employers, which involved collection of information on employees' access to FSLPs and monthly experience with ILI and workplace attendance from November 2007 to April 2008. Multivariate analyses were used to estimate the impact of FSLPs on employees' workplace attendance while they were experiencing severe ILI symptoms. Among 793 employees with ILI, the average duration of severe ILI symptoms was 3.0 days. Most employees (71.9%) attended work with severe ILI symptoms, for an average of 1.3 days. Employees who could telework had a 29.7% lower rate of attending work with severe ILI symptoms (P = 0.026). Employers that implement teleworking policies may be able to reduce employee-to-employee transmission of respiratory illness, including seasonal and pandemic influenza.

• Benefits and risks of live attenuated influenza vaccine in young children.

  Authors: Gerry Oster, Derek Weycker, John Edelsberg, Kristin L Nichol, Jerome O Klein, Robert B Belshe

  The American journal of managed care. 09/2010; 16(9):e235-44.

  To examine the benefit-risk profile of live attenuated influenza vaccine (LAIV) across a range of clinical scenarios in which we varied assumptions regarding both the percentage of children who wouldTo examine the benefit-risk profile of live attenuated influenza vaccine (LAIV) across a range of clinical scenarios in which we varied assumptions regarding both the percentage of children who would receive LAIV in lieu of trivalent inactivated influenza virus (TIV) and the extent of off-label use. Model of expected benefits and risks of immunization of young children against influenza. We estimated expected numbers of cases of influenza illness (FLU), medically significant wheezing (MSW), and hospitalization in a single influenza season under alternative assumptions regarding use of LAIV in lieu of TIV, based on projections from a large phase III trial. Assuming no use of LAIV in nonindicated children (aged <24 months and those with history of recurrent wheezing or asthma), and 50% use in lieu of TIV among children in the indicated population, there would be 2099 fewer FLU cases per 100,000 children aged 12 to 59 months, and no change in MSW or hospitalization. If LAIV also were used in lieu of TIV among 20% of children aged 12 to 23 months and 20% of children aged 24 to 59 months with a history of recurrent wheezing or asthma, there would be a further reduction of 397 FLU cases and 12 hospitalizations per 100,000 children aged 12 to 59 months, but 51 additional MSW cases. Our study suggests that even if LAIV were sometimes used inadvertently in clinical practice in young children for whom it is not indicated, the overall balance of expected benefits and risks would remain favorable.

• Employees' willingness to pay to prevent influenza.

  Authors: Stephen S Johnston, Matthew D Rousculp, Liisa A Palmer, Bong-Chul Chu, Parthiv J Mahadevia, Kristin L Nichol

  The American journal of managed care. 08/2010; 16(8):e205-14.

  To quantify employees' preferences, as measured by willingness to pay, to prevent influenza in themselves and in their child and adult household members and to examine factors associated withTo quantify employees' preferences, as measured by willingness to pay, to prevent influenza in themselves and in their child and adult household members and to examine factors associated with willingness to pay. Prospective observational cohort study of a convenience sample of employees from 3 large US employers. Participants had at least 1 child (< or = 17 years) living in their household for at least 4 days per week. Each month from November 2007 to April 2008, employees completed Web-based surveys regarding acute respiratory illness in their household. In the final survey, employees were presented with descriptions of influenza and questions regarding their willingness to pay to prevent influenza. Factors associated with willingness to pay were examined using multivariate ordinary least squares regression analysis of the log of willingness to pay. Among 2006 employees, 31.3% were female, the mean age was 41.7 years, 85.3% were of white race/ethnicity, and the mean household size was 4.0. Employees' median (mean) willingness to pay to prevent influenza was $25 ($72) for themselves, $25 ($82) for their adult household members, and $50 ($142) (P <.01) for children. However, influenza vaccination rates were approximately equal for children (27.5%), employees (31.5%), and other adult household members (24.5%). This finding may be explained by barriers such as cost, dislike of vaccinations, and disagreement with national influenza vaccination recommendations, which were significantly associated with lower willingness to pay for prevention of influenza (P <.05). Employees expressed a stronger preference to prevent influenza in their children than in themselves or other household members; however, modifiable barriers depress vaccination rates.

• Effect of influenza-like illness and other wintertime respiratory illnesses on worker productivity: The child and household influenza-illness and employee function (CHIEF) study.

  Authors: Liisa A Palmer, Matthew D Rousculp, Stephen S Johnston, Parthiv J Mahadevia, Kristin L Nichol

  Vaccine. 07/2010; 28(31):5049-56.

  Acute respiratory illnesses (ARI), comprising influenza-like illness (ILI) and other wintertime respiratory illnesses (ORI), impose substantial health and economic burdens on the United States.Acute respiratory illnesses (ARI), comprising influenza-like illness (ILI) and other wintertime respiratory illnesses (ORI), impose substantial health and economic burdens on the United States. Little is known about the impact of ILI among household members (HHM), particularly children, on employees' productivity. To quantify the impact of employee and HHM-ILI and ARI on employee productivity, a prospective, observational cohort study was conducted among employees from three large US companies. Employees who had at least one child living at home (N=2013) completed a monthly survey during the 2007-2008 influenza season, reporting the number of days missed from work and hours of presenteeism due to: (1) personal ILI, (2) HHM-ILI, and (3) personal and HHM-ARI. Employee ILI ranged from 4.8% (April) to 13.5% (February). Employees reporting ILI reported more absences than employees not reporting ILI (72% vs 30%, respectively; P<0.001). Overall, 61.2% of employees surveyed had at least one child with an ILI; these employees missed more days of work due to HHM illness than employees without an ARI-ill child (0.9 days vs 0.3 days, respectively; P<0.001). Employees with ILI were less productive, on average, for 4.8h each day that they worked while sick, 2.5h of which was attributable to ILI. HHM illnesses accounted for 17.7% (1389/7868 days) of employee absenteeism, over half of which was due to HHM-ARI. ILI causes a significant amount of employee absence. Household members, particularly children, comprise a sizable proportion of general illness and injury-related employee absences.

• Pneumococcal vaccination and revaccination in the elderly population.

  Authors: Kristin L Nichol

  The Journal of infectious diseases. 03/2010; 201(5):659-61.

• Sensitivity analyses to estimate the potential impact of unmeasured confounding in causal research.

  Authors: Rolf H H Groenwold, David B Nelson, Kristin L Nichol, Arno W Hoes, Eelko Hak

  International journal of epidemiology. 11/2009;

  BACKGROUND: The impact of unmeasured confounders on causal associations can be studied by means of sensitivity analyses. Although several sensitivity analyses are available, these are usedBACKGROUND: The impact of unmeasured confounders on causal associations can be studied by means of sensitivity analyses. Although several sensitivity analyses are available, these are used infrequently. This article is intended as a tutorial on sensitivity analyses, in which we discuss three methods to conduct sensitivity analysis. METHODS: Each method is based on assumed associations between confounder and exposure, confounder and outcome and the prevalence of the confounder in the population at large. In the first method an unmeasured confounder is simulated and subsequently adjusted. The other two methods are analytical methods, in which either the (adjusted) effect estimate is multiplied with a factor based on assumed confounder characteristics, or the (adjusted) risks for the outcome among exposed and unexposed subjects are adjusted by such a factor. These methods are illustrated with a clinical example on influenza vaccine effectiveness. RESULTS: When applied to a dataset constructed to assess the effect of influenza vaccination on mortality, the three reviewed methods provided similar results. After adjustment for observed confounders, influenza vaccination reduced mortality by 42% [odds ratio (OR) 0.58, 95% confidence interval (CI) 0.46-0.73]. To arrive at a 95% CI including one requires a very common confounder (40% prevalence) with strong associations with both vaccination status and mortality, respectively OR </=0.3 and OR >/=3.0 (OR 0.79, 95% CI 0.62-1.00). CONCLUSIONS: In every non-randomized study on causal associations the robustness of the results with respect to unmeasured confounding can, and should, be assessed using sensitivity analyses.

• Challenges in evaluating influenza vaccine effectiveness and the mortality benefits controversy.

  Authors: Kristin L Nichol

  Vaccine. 10/2009; 27(45):6305-11.

  Randomized, controlled trials are the gold standard study design. However, ethical constraints and practical considerations may necessitate other types of studies for evaluating influenza vaccineRandomized, controlled trials are the gold standard study design. However, ethical constraints and practical considerations may necessitate other types of studies for evaluating influenza vaccine effectiveness in the elderly--a high priority group for annual vaccination in many countries. Observational studies therefore comprise the bulk of the vaccine effectiveness evidence in older persons, but these types of studies can be susceptible to selection bias and residual confounding. All observational studies should utilize strategies to minimize the impact of bias and confounding. Recent studies questioning the plausibility of reported mortality benefits among vaccinated elderly persons may themselves be based on assumptions that are susceptible to important limitations and multiple biases. Future studies that incorporate prospectively collected information on functional status, life expectancy, and other types of data may provide additional insights into these concerns. At present, even after taking into account the potential for residual bias and confounding, most studies confirm the benefits of vaccination among the elderly for reducing hospitalization and death.

• Human Coronavirus and Acute Respiratory Illness in Older Adults with Chronic Obstructive Pulmonary Disease.

  Authors: Geoffrey J Gorse, Theresa Z O'Connor, Susan L Hall, Joseph N Vitale, Kristin L Nichol

  The Journal of infectious diseases. 04/2009; 199(6):847-857.

  Background. The clinical features and incidence of human coronavirus (HCoV) infections in chronically ill older adults need better definition. Methods. HCoV infection was determined on the basis of aBackground. The clinical features and incidence of human coronavirus (HCoV) infections in chronically ill older adults need better definition. Methods. HCoV infection was determined on the basis of a 4-fold increase in serum antibody and the detection of HCoV by reverse-transcription polymerase chain reaction. Laboratory-documented influenza (LDI) was detected by serologic assay and culture. HCoV illnesses were compared with other acute respiratory illnesses identified by active surveillance, during the 1998-99 winter respiratory-virus season, of 2215 patients with chronic obstructive pulmonary disease who were 50 years old and who received influenza vaccines. Results. HCoV-229E and HCoV-OC43 were associated with 90 (14%) of 665 illnesses (HCoV-229E in 22, HCoV-OC43 in 67, and both in 1), LDI with 107 (16%) of 678 illnesses. In multivariate logistic regression analysis, myalgia was less likely with HCoV infection than with LDI (OR, 0.27 [95% confidence limit, 0.13-0.58]). A majority of these HCoV and LDI illnesses exhibited each of 11 symptoms and signs of acute respiratory illness. Spirometric results worsened most often with LDI, and many acute respiratory illnesses, regardless of etiology, were associated with hospitalization. A total of 8 illnesses were associated with HCoV-NL63, 1 with HCoV-HKU1. Conclusions. The frequencies of HCoV and LDI illnesses were similar. HCoV illness was less severe than LDI illness, was accompanied by multiple respiratory and systemic symptoms, and was associated with hospitalization.

• Influenza vaccination among college and university students: impact on influenzalike illness, health care use, and impaired school performance.

  Authors: Kristin L Nichol, Sarah D'Heilly, Edward P Ehlinger

  Archives of pediatrics & adolescent medicine. 01/2009; 162(12):1113-8.

  OBJECTIVE: To assess influenza vaccine effectiveness against influenzalike illness (ILI) and ILI impact on health care use and school performance among college and university students. DESIGN: PooledOBJECTIVE: To assess influenza vaccine effectiveness against influenzalike illness (ILI) and ILI impact on health care use and school performance among college and university students. DESIGN: Pooled analysis of 4 consecutive cohorts for the 2002-2003 through 2005-2006 seasons. SETTING: Twin Cities campus of the University of Minnesota (2002-2003 through 2005-2006 seasons) and St. Olaf College in Northfield, Minnesota (2005-2006 season). PARTICIPANTS: Full-time students received e-mail invitations to participate in single-season cohorts. Internet-based surveys collected baseline (October) and follow-up (November-April) data. Main Exposure Influenza vaccination. Main Outcome Measure Proportion of students with ILI. Multivariable regression models assessed the effectiveness of vaccination for reducing ILI during months when influenza was circulating while controlling for confounders and after pooling data across the 4 cohorts. RESULTS: There were 2804, 2783, 3534, and 3674 participants in the 2002-2003, 2003-2004, 2004-2005, and 2005-2006 cohorts respectively, and overall, 30.2% were vaccinated. In the pooled analysis, 24.1% of students experienced at least 1 ILI during influenza seasons. Vaccination was associated with a significant reduction in the likelihood of ILI during influenza seasons (adjusted odds ratio, 0.70; 95% confidence interval, 0.56-0.89) but not during noninfluenza periods (adjusted odds ratio, 0.98; 95% confidence interval, 0.73-1.30). Vaccination was also associated with significant reductions in ILI-associated provider visits, antibiotic use, impaired school performance, and numbers of days of missed class, missed work, and illness during the influenza seasons. CONCLUSIONS: Influenza vaccination was associated with substantial reductions in ILI and ILI-associated health care use and impairment of school performance. College and university students can experience substantial benefits from influenza vaccinations.

• Burden of Influenza-Like Illness and Effectiveness of Influenza Vaccination among Working Adults Aged 50-64 Years.

  Authors: Kristin L Nichol, Sarah J D'Heilly, Michael E Greenberg, Edward Ehlinger

  Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 01/2009;

  Background. @nbsp; Uncertainties regarding influenza disease impact and benefits of vaccination may contribute to low vaccination rates among adults aged 50-64 years. Methods. @nbsp; This prospectiveBackground. @nbsp; Uncertainties regarding influenza disease impact and benefits of vaccination may contribute to low vaccination rates among adults aged 50-64 years. Methods. @nbsp; This prospective cohort study assessed the burden of influenza-like illness (ILI) among working adults aged 50-64 years and the effectiveness of influenza vaccination in reducing the rate of ILI and productivity losses. Employees of the University of Minnesota (Minneapolis) were invited via e-mail to participate in the study during October 2006. The study data were collected using internet-based surveys at baseline (October 2006) and during the follow-up period (from November 2006 through April 2007). Months included in the 2006-2007 influenza season were identified retrospectively from Minnesota Department of Health surveillance data. Vaccine effectiveness for reducing the rate of ILI, ILI-associated health care use, the number of days of illness, work loss, and reduced on-the-job productivity during the influenza season were assessed using multivariable regression models after controlling for important confounders. Results. @nbsp; Four hundred ninety-seven persons were included in the study, 85 (17.1%) of whom experienced an ILI. Among unvaccinated participants, ILI was responsible for 45% of all days of illness during the influenza season, 39% of all illness-related work days lost, and 49% of all days with illness-related reduced on-the-job productivity. In the multivariable regression analyses, vaccination was associated with a significant reduction in the rate of ILI (adjusted odds ratio, 0.48; 95% confidence interval, 0.27-0.86) and fewer days of illness, absenteeism, and impaired on-the-job performance. Conclusion. @nbsp; ILIs were common among our study participants, accounting for a large portion of illness, work loss, and impaired work performance during the influenza season. Vaccination was associated with substantial health and productivity benefits. Vaccine delivery should be improved for this high-priority group.

• Efficacy and effectiveness of influenza vaccination.

  Authors: Kristin L Nichol

  Vaccine. 10/2008; 26 Suppl 4:D17-22.

  Influenza is a major causeof morbidity and mortality. Vaccination remains the most important means of preventing and controlling influenza. A review of the published literature shows that vaccinationInfluenza is a major causeof morbidity and mortality. Vaccination remains the most important means of preventing and controlling influenza. A review of the published literature shows that vaccination of children, healthy younger adults, the elderly, and both children and adults with high-risk medical conditions provides substantial benefits, although the types of benefits vary by age. Vaccination also generally provides benefit even during poor match seasons. Strategies to reduce transmission within households and communities throughthe vaccination of school children and to reduce transmission within health care settings through the vaccination of healthcare workers are also promising. Published by Elsevier Ltd.

• Decline in influenza-associated mortality among Dutch elderly following the introduction of a nationwide vaccination program.

  Authors: Angelique G S C Jansen, Elisabeth A M Sanders, Kristin L Nichol, Anton M van Loon, Arno W Hoes, Eelko Hak

  Vaccine. 09/2008;

  With a retrospective nationwide cohort study in the Netherlands over 1992-2003, using mortality and viral surveillance data, the aim was to assess by means of rate difference methods theWith a retrospective nationwide cohort study in the Netherlands over 1992-2003, using mortality and viral surveillance data, the aim was to assess by means of rate difference methods the influenza-associated mortality in the elderly before and after the introduction of a nationwide influenza vaccination program in 1996 (vaccination coverage raised from below 50 to 80%). The average annual influenza-associated mortality declined in the years before and after the introduction from 131 to 105 per 100,000 persons (relative risk 0.80). The decline was largest in the age group 65-69 years (relative risk 0.54) and less in those aged 75 years and older. Validation by Serfling-type regression analysis revealed similar results. In conclusion, routine influenza vaccination among Dutch elderly was associated with a significant decrease in influenza-associated mortality, notably in those aged 65-69 years.

• Cost-effectiveness of live attenuated influenza vaccine versus inactivated influenza vaccine among children aged 24-59 months in the United States.

  Authors: Bryan R Luce, Kristin L Nichol, Robert B Belshe, Kevin D Frick, Su Xia Li, Audra Boscoe, Matthew D Rousculp, Parthiv J Mahadevia

  Vaccine. 07/2008; 26(23):2841-8.

  BACKGROUND: The US Advisory Committee on Immunization Practices (ACIP) recently expanded the influenza vaccine recommendation to include children 24-59 months of age. In a large head-to-headBACKGROUND: The US Advisory Committee on Immunization Practices (ACIP) recently expanded the influenza vaccine recommendation to include children 24-59 months of age. In a large head-to-head randomized controlled trial, live attenuated influenza vaccine, trivalent (LAIV) demonstrated a 54% relative reduction in culture-confirmed influenza illness compared with trivalent inactivated influenza vaccine (TIV) among children aged 24-59 months. OBJECTIVE: To evaluate the relative cost and benefit between two influenza vaccines (LAIV and TIV) for healthy children 24-59 months of age. METHODS: Using patient-level data from the clinical trial supplemented with cost data from published literature, we modeled the cost-effectiveness of these two vaccines. Effectiveness was measured in quality-adjusted life years (QALY) and cases of influenza avoided. The analysis used the societal perspective. RESULTS: Due to its higher acquisition cost, LAIV increased vaccination costs by USD7.72 per child compared with TIV. However, compared with TIV, LAIV reduced the number of influenza illness cases and lowered the subsequent healthcare use of children and productivity losses of parents. The estimated offsets in direct and indirect costs saved USD15.80 and USD37.72 per vaccinated child, respectively. LAIV had a net total cost savings of USD45.80 per child relative to TIV. One-way and probabilistic sensitivity analyses indicated that the model was robust across a wide range of relative vaccine efficacy and cost estimates. CONCLUSIONS: Due to its increased relative vaccine efficacy over TIV, LAIV reduced the burden of influenza and lowered both direct health care and societal costs among children 24-59 months of age.

• Rapid diagnosis of influenza infection in older adults: Influence on clinical care in a routine clinical setting.

  Authors: Sarah J D'Heilly, Edward N Janoff, Paul Nichol, Kristin L Nichol

  Journal of clinical virology : the official publication of the Pan American Society for Clinical Virology. 06/2008; 42(2):124-8.

  BACKGROUND: Laboratory diagnosis of influenza has previously relied on viral isolation in culture. Rapid antigen tests (RATs) are now available but few studies have examined their use in older adultsBACKGROUND: Laboratory diagnosis of influenza has previously relied on viral isolation in culture. Rapid antigen tests (RATs) are now available but few studies have examined their use in older adults under routine clinical conditions. OBJECTIVES: To determine the utility of the RAT in older adults presenting to a large medical center and how test results impacted clinical care. STUDY DESIGN: Retrospective chart review of patients tested for influenza during the 2003-2004 and 2004-2005 influenza seasons. Clinical data were correlated with the results of laboratory testing. RESULTS: Eighty-four adults tested positive for influenza. Adding the results of the RAT to symptom complexes predictive of influenza significantly enhanced the ability to diagnose influenza in the acute setting. The positive predictive value of fever plus cough increased from 32% to 92% with a positive RAT. The RAT also directed appropriate antiviral therapy. 20/22 (91%) patients with a positive RAT and symptoms </=48h received antiviral treatment compared to only 1/12 (8%) patients with a negative RAT and a positive culture. CONCLUSIONS: Under routine clinical conditions rapid influenza testing enhances the ability to quickly diagnose influenza and can be used to guide early treatment decisions in older adults.

• Effectiveness of influenza vaccine in the community-dwelling elderly.

  Authors: Kristin L Nichol, James D Nordin, David B Nelson, John P Mullooly, Eelko Hak

  The New England journal of medicine. 11/2007; 357(14):1373-81.

  BACKGROUND: Reliable estimates of the effectiveness of influenza vaccine among persons 65 years of age and older are important for informed vaccination policies and programs. Short-term studies mayBACKGROUND: Reliable estimates of the effectiveness of influenza vaccine among persons 65 years of age and older are important for informed vaccination policies and programs. Short-term studies may provide misleading pictures of long-term benefits, and residual confounding may have biased past results. This study examined the effectiveness of influenza vaccine in seniors over the long term while addressing potential bias and residual confounding in the results. METHODS: Data were pooled from 18 cohorts of community-dwelling elderly members of one U.S. health maintenance organization (HMO) for 1990-1991 through 1999-2000 and of two other HMOs for 1996-1997 through 1999-2000. Logistic regression was used to estimate the effectiveness of the vaccine for the prevention of hospitalization for pneumonia or influenza and death after adjustment for important covariates. Additional analyses explored for evidence of bias and the potential effect of residual confounding. RESULTS: There were 713,872 person-seasons of observation. Most high-risk medical conditions that were measured were more prevalent among vaccinated than among unvaccinated persons. Vaccination was associated with a 27% reduction in the risk of hospitalization for pneumonia or influenza (adjusted odds ratio, 0.73; 95% confidence interval [CI], 0.68 to 0.77) and a 48% reduction in the risk of death (adjusted odds ratio, 0.52; 95% CI, 0.50 to 0.55). Estimates were generally stable across age and risk subgroups. In the sensitivity analyses, we modeled the effect of a hypothetical unmeasured confounder that would have caused overestimation of vaccine effectiveness in the main analysis; vaccination was still associated with statistically significant--though lower--reductions in the risks of both hospitalization and death. CONCLUSIONS: During 10 seasons, influenza vaccination was associated with significant reductions in the risk of hospitalization for pneumonia or influenza and in the risk of death among community-dwelling elderly persons. Vaccine delivery to this high-priority group should be improved.

• Improving influenza vaccination rates among adults.

  Authors: Kristin L Nichol

  Cleveland Clinic journal of medicine. 12/2006; 73(11):1009-15.

  Influenza remains an important cause of illness and death in this country. Even though we have safe and effective vaccines, vaccination rates among the elderly and other high-risk groups remainInfluenza remains an important cause of illness and death in this country. Even though we have safe and effective vaccines, vaccination rates among the elderly and other high-risk groups remain static and well below national goals. Health care providers can boost these vaccination rates by educating themselves, by recommending that their patients be vaccinated, and by implementing evidence-based strategies such as programs to remind themselves and patients to be vaccinated, to utilize standing orders for nurses or other qualified professionals to offer and administer vaccines, and to provide feedback on performance. We should also consider alternative paradigms for vaccine delivery, and be sure to be vaccinated ourselves.

• Heterogeneity of influenza case definitions and implications for interpreting and comparing study results.

  Authors: Kristin L Nichol

  Vaccine. 12/2006; 24(44-46):6726-8.

  There is substantial heterogeneity with regard to influenza case definitions used in the medical literature. These different case definitions can vary substantially with regard to their sensitivity,There is substantial heterogeneity with regard to influenza case definitions used in the medical literature. These different case definitions can vary substantially with regard to their sensitivity, specificity and positive and negative predictive values for confirmed influenza. Because of this heterogeneity, it is important that the appropriate case definitions be used to answer the specific questions of the study, with more specific definitions likely being used to answer questions of vaccine efficacy and more sensitive definitions being used to assess overall disease burden. When interpreting the results of studies and comparing results across studies it is essential that the issue of heterogeneity of case definitions be addressed, and that absolute risk reduction be used as the main outcome measure of interest rather than just the relative risk reduction.