Do hospital employees benefit from the influenza vaccine? A placebo-controlled clinical trial

Effect of a multimodal strategy for prevention of nosocomial influenza: a retrospective study at Grenoble Alpes University Hospital from 2014 to 2019

Background

A multimodal strategy to prevent nosocomial influenza was implemented in 2015–2016 in Grenoble Alpes University Hospital. Three modalities were implemented in all units: promotion of vaccination among healthcare workers, epidemiologic surveillance and communication campaigns. Units receiving a high number of patients with influenza implemented 2 additional modalities: improvement of diagnosis capacities and systematic surgical mask use. The main objective was to assess the effectiveness of the strategy for reducing the risk of nosocomial influenza.

Methods

A study was conducted retrospectively investigating 5 epidemic seasons (2014–2015 to 2018–2019) including all patients hospitalized with a positive influenza test at Grenoble Alpes University Hospital. The weekly number of nosocomial influenza cases was analyzed by Poisson regression and incidence rate ratios (IRR) were estimated.

Results

A total of 1540 patients, resulting in 1559 stays, were included. There was no significant difference between the 5 influenza epidemic seasons in the units implementing only 3 measures. In the units implementing the 5 measures, there was a reduction of nosocomial influenza over the seasons when the strategy was implemented compared to the 2014–2015 epidemic season (IRR = 0.56, 95% CI = 0.23–1.34 in 2015–2016; IRR = 0.39, 95% CI = 0.19–0.81 in 2016–2017; IRR = 0.50, 95% CI = 0.24–1.03 in 2017–2018; IRR = 0.48, 95% CI = 0.23–0.97 in 2018–2019).

Conclusions

Our data mainly suggested that the application of the strategy with 5 modalities, including systematic surgical mask use and rapid diagnosis, seemed to reduce by half the risk of nosocomial influenza. Further data, including medico-economic studies, are necessary to determine the opportunity of extending these measures at a larger scale.

A Systematic Review and Meta-Analysis of Seasonal Influenza Vaccination of Health Workers

A systematic review and meta-analysis was conducted to estimate the pooled effect of influenza vaccinations for health workers (HWs). Nine databases were screened to identify randomized clinical trials and comparative observational studies that reported the effect of influenza vaccination among HWs. The risk ratio (RR), standardized mean difference, and 95% confidence interval (CI) were employed to study the effect size using fixed/random-effect models. Subgroup analyses and sensitivity analyses were conducted accordingly. Publication bias was examined. Sixteen studies (involving 7971 HWs from nine countries) were included after a comprehensive literature search. The combined RR regarding the incidence of laboratory-confirmed influenza was 0.36 (95% CI: 0.25 to 0.54), the incidence of influenza-like illness (ILI) was 0.69 (95% CI: 0.45 to 1.06), the absenteeism rate was 0.63 (95% CI: 0.46 to 0.86), and the integrated standardized mean difference of workdays lost was −0.18 (95% CI: −0.28 to −0.07) days/person. The subgroup analysis indicated that vaccination significantly decreases the incidence of laboratory-confirmed influenza in different countries, study populations, and average-age vaccinated groups. Influenza vaccinations could effectively reduce the incidence of laboratory-confirmed influenza, absenteeism rates, and workdays lost among HWs. It is advisable, therefore, to improve the coverage and increase the influenza vaccination count among HWs, which may benefit both workers and medical institutions.

A rapid evidence appraisal of influenza vaccination in health workers: An important policy in an area of imperfect evidence

INTRODUCTION

The World Health Organization recommends vaccination of health workers (HWs) against influenza, but low uptake is intransigent.We conducted a Rapid Evidence Appraisal on: the risk of influenza in HWs, transmission risk from HWs to patients, the benefit of HW vaccination, and strategies for improving uptake. We aimed to capture a 'whole-of-system' perspective to consider possible benefits for HWs, employers and patients.

METHODS

We executed a comprehensive search of the available literature published from 2006 to 2018 in the English language. We developed search terms for seven separate questions following the PICO framework (population, intervention, comparators, outcomes) and queried nine databases.

RESULTS

Of 3784 publications identified, 52 met inclusion criteria. Seven addressed HW influenza risk, of which four found increased risk; 15 addressed influenza vaccine benefit to HWs or their employers, of which 10 found benefit; 11 addressed influenza transmission from HWs to patients, of which 6 found evidence for transmission; 12 unique studies addressed whether vaccinating HWs produced patient benefit, of which 9 concluded benefits accrued. Regarding the number of HWs needed to vaccinate (NNV) to deliver patient benefit, NNV estimates ranged from 3 to 36,000 but were in significant disagreement. Fourteen studies provided insights on strategies to improve uptake; the strongest evidence was for mandatory vaccination.

CONCLUSIONS

The evidence on most questions related to influenza vaccination in HWs is mixed and often of low-quality. Substantial heterogeneity exists in terms of study designs and settings, making comparison between studies difficult. Notwithstanding these limitations, a majority of studies suggests that influenza vaccination benefit HWs and their employers; and HWs are implicated in transmission events. The effects of vaccinating HWs on patient morbidity and mortality may include reductions in all-cause mortality and influenza-like illness (ILI). Taken together, the evidence suggests that HW vaccination is an important policy for HWs themselves, their employers, and their patients.

A systematic review and meta-analysis of the direct epidemiological and economic effects of seasonal influenza vaccination on healthcare workers

BACKGROUND

Influenza vaccination is a commonly used intervention to prevent influenza infection in healthcare workers (HCWs) and onward transmission to other staff and patients. We undertook a systematic review to synthesize the latest evidence of the direct epidemiological and economic effectiveness of seasonal influenza vaccination among HCW.

METHODS

We conducted a systematic search of MEDLINE/PubMed, Scopus, and Cochrane Central Register of Controlled Trials from 1980 through January 2018. All studies comparing vaccinated and non-vaccinated (i.e. placebo or non-intervention) groups of HCWs were included. Research articles that focused on only patient-related outcomes or monovalent A(H1N1)pdm09 vaccines were excluded. Two reviewers independently selected articles and extracted data. Pooled-analyses were conducted on morbidity outcomes including laboratory-confirmed influenza, influenza-like illnesses (ILI), and absenteeism. Economic studies were summarized for the characteristics of methods and findings.

RESULTS

Thirteen articles met eligibility criteria: three articles were randomized controlled studies and ten were cohort studies. Pooled results showed a significant effect on laboratory-confirmed influenza incidence but not ILI. While the overall incidence of absenteeism was not changed by vaccine, ILI absenteeism was significantly reduced. The duration of absenteeism was also shortened by vaccination. All published economic evaluations consistently found that the immunization of HCW was cost saving based on crude estimates of avoided absenteeism by vaccination. No studies, however, comprehensively evaluated both health outcomes and costs of vaccination programs to examine cost-effectiveness.

DISCUSSION

Our findings reinforced the influenza vaccine effects in reducing infection incidence and length of absenteeism. A better understanding of the incidence of absenteeism and comprehensive economic program evaluations are required to ensure the best possible management of ill HCWs and the investment in HCW immunization in increasingly constrained financial environments. These steps are fundamental to establish sustainability and cost-effectiveness of vaccination programs and underpin HCW immunization policy.

Vaccines for preventing influenza in healthy adults

BACKGROUND

The consequences of influenza in adults are mainly time off work. Vaccination of pregnant women is recommended internationally. This is an update of a review published in 2014. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE (January 1966 to 31 December 2016), Embase (1990 to 31 December 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017), as well as checking the bibliographies of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. Previous versions of this review included observational comparative studies assessing serious and rare harms cohort and case-control studies. Due to the uncertain quality of observational (i.e. non-randomised) studies and their lack of influence on the review conclusions, we decided to update only randomised evidence. The searches for observational comparative studies are no longer updated.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We rated certainty of evidence for key outcomes (influenza, influenza-like illness (ILI), hospitalisation, and adverse effects) using GRADE.

MAIN RESULTS

We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines. We have presented findings from 25 studies comparing inactivated parenteral influenza vaccine against placebo or do-nothing control groups as the most relevant to decision-making. The studies were conducted over single influenza seasons in North America, South America, and Europe between 1969 and 2009. We did not consider studies at high risk of bias to influence the results of our outcomes except for hospitalisation.Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vaccination to 0.9% (risk ratio (RR) 0.41, 95% confidence interval (CI) 0.36 to 0.47; 71,221 participants; moderate-certainty evidence), and they probably reduce ILI from 21.5% to 18.1% (RR 0.84, 95% CI 0.75 to 0.95; 25,795 participants; moderate-certainty evidence; 71 healthy adults need to be vaccinated to prevent one of them experiencing influenza, and 29 healthy adults need to be vaccinated to prevent one of them experiencing an ILI). The difference between the two number needed to vaccinate (NNV) values depends on the different incidence of ILI and confirmed influenza among the study populations. Vaccination may lead to a small reduction in the risk of hospitalisation in healthy adults, from 14.7% to 14.1%, but the CI is wide and does not rule out a large benefit (RR 0.96, 95% CI 0.85 to 1.08; 11,924 participants; low-certainty evidence). Vaccines may lead to little or no small reduction in days off work (-0.04 days, 95% CI -0.14 days to 0.06; low-certainty evidence). Inactivated vaccines cause an increase in fever from 1.5% to 2.3%.We identified one RCT and one controlled clinical trial assessing the effects of vaccination in pregnant women. The efficacy of inactivated vaccine containing pH1N1 against influenza was 50% (95% CI 14% to 71%) in mothers (NNV 55), and 49% (95% CI 12% to 70%) in infants up to 24 weeks (NNV 56). No data were available on efficacy against seasonal influenza during pregnancy. Evidence from observational studies showed effectiveness of influenza vaccines against ILI in pregnant women to be 24% (95% CI 11% to 36%, NNV 94), and against influenza in newborns from vaccinated women to be 41% (95% CI 6% to 63%, NNV 27).Live aerosol vaccines have an overall effectiveness corresponding to an NNV of 46. The performance of one- or two-dose whole-virion 1968 to 1969 pandemic vaccines was higher (NNV 16) against ILI and (NNV 35) against influenza. There was limited impact on hospitalisations in the 1968 to 1969 pandemic (NNV 94). The administration of both seasonal and 2009 pandemic vaccines during pregnancy had no significant effect on abortion or neonatal death, but this was based on observational data sets.

AUTHORS' CONCLUSIONS

Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalisations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review.Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenza vaccination and serious adverse events in the comparative studies considered in this review. Fifteen included RCTs were industry funded (29%).

Estimation of sickness absenteeism among Italian healthcare workers during seasonal influenza epidemics

OBJECTIVES

To analyze absenteeism among healthcare workers (HCWs) at a large Italian hospital and to estimate the increase in absenteeism that occurred during seasonal flu periods.

DESIGN

Retrospective observational study.

METHODS

The absenteeism data were divided into three "epidemic periods," starting at week 42 of one year and terminating at week 17 of the following year (2010-2011, 2011-2012, 2012-2013), and three "non-epidemic periods," defined as week 18 to week 41 and used as baseline data. The excess of the absenteeism occurring among HCWs during periods of epidemic influenza in comparison with baseline was estimated. All data, obtained from Hospital's databases, were collected for each of the following six job categories: medical doctors, technical executives (i.e., pharmacists), nurses and allied health professionals (i.e., radiographers), other executives (i.e., engineers), nonmedical support staff, and administrative staff. The HCWs were classified by: in and no-contact; vaccinated and unvaccinated.

RESULTS

5,544, 5,369, and 5,291 workers in three years were studied. The average duration of absenteeism during the epidemic periods increased among all employees by +2.07 days/person (from 2.99 to 5.06), and the relative increase ranged from 64-94% among the different job categories. Workers not in contact with patients experienced a slightly greater increase in absenteeism (+2.28 days/person, from 2.73 to 5.01) than did employees in contact with patients (+2.04, from 3.04 to 5.08). The vaccination rate among HCWs was below 3%, however the higher excess of absenteeism rate among unvaccinated in comparison with vaccinated workers was observed during the epidemic periods (2.09 vs 1.45 days/person).

CONCLUSION

The influenza-related absenteeism during epidemic periods was quantified as totaling more than 11,000 days/year at the Italian hospital studied. This result confirms the economic impact of sick leave on healthcare systems and stresses on the necessity of encouraging HCWs to be immunized against influenza.

Regulatory mechanisms for absenteeism in the health sector: a systematic review of strategies and their implementation

BACKGROUND

A systematic review was undertaken to identify regulatory mechanisms aimed at mitigating health care worker absenteeism, to describe where and how they have been implemented as well as their possible effects. The goal was to propose potential policy options for managing the problem of absenteeism among human resources for health in low- and middle-income countries. Mechanisms described in this review are at the local workplace and broader national policy level.

METHODS

A comprehensive online search was conducted on EMBASE, CINAHL, PubMed, Google Scholar, Google, and Social Science Citation Index using MEDLINE search terms. Retrieved studies were uploaded onto reference manager and screened by two independent reviewers. Only publications in English were included. Data were extracted and synthesized according to the objectives of the review.

RESULTS

Twenty six of the 4,975 published articles retrieved were included. All were from high-income countries and covered all cadres of health workers. The regulatory mechanisms and possible effects include 1) organizational-level mechanisms being reported as effective in curbing absenteeism in low- and middle-income countries (LMICs); 2) prohibition of private sector activities in LMICs offering benefits but presenting a challenge for the government to monitor the health workforce; 3) contractual changes from temporary to fixed posts having been associated with no reduction in absenteeism and not being appropriate for LMICs; 4) multifaceted work interventions being implemented in most settings; 5) the possibility of using financial and incentive regulatory mechanisms in LMICs; 6) health intervention mechanisms reducing absenteeism when integrated with exercise programs; and 7) attendance by legislation during emergencies being criticized for violating human rights in the United States and not being effective in curbing absenteeism.

CONCLUSION

Most countries have applied multiple strategies to mitigate health care worker absenteeism. The success of these interventions is heavily influenced by the context within which they are applied.

Influenza vaccination for healthcare workers in the UK: appraisal of systematic reviews and policy options

BACKGROUND

The UK Department of Health recommends annual influenza vaccination for healthcare workers, but uptake remains low. For staff, there is uncertainty about the rationale for vaccination and evidence underpinning the recommendation.

OBJECTIVES

To clarify the rationale, and evidence base, for influenza vaccination of healthcare workers from the occupational health, employer and patient safety perspectives.

DESIGN

Systematic appraisal of published systematic reviews.

RESULTS

The quality of the 11 included reviews was variable; some included exactly the same trials but made conflicting recommendations. 3 reviews assessed vaccine effects in healthcare workers and found 1 trial reporting a vaccine efficacy (VE) of 88%. 6 reviews assessed vaccine effects in healthy adults, and VE was consistent with a median of 62% (95% CI 56 to 67). 2 reviews assessed effects on working days lost in healthcare workers (3 trials), and 3 reported effects in healthy adults (4 trials). The meta-analyses presented by the most recent reviews do not reach standard levels of statistical significance, but may be misleading as individual trials suggest benefit with wide variation in size of effect. The 2013 Cochrane review reported absolute effects close to 0 for laboratory-confirmed influenza, and hospitalisation for patients, but excluded data on clinically suspected influenza and all-cause mortality, which had shown potentially important effects in previous editions. A more recent systematic review reports these effects as a 42% reduction in clinically suspected influenza (95% CI 27 to 54) and a 29% reduction in all-cause mortality (95% CI 15 to 41).

CONCLUSIONS

The evidence for employer and patient safety benefits of influenza vaccination is not straightforward and has been interpreted differently by different systematic review authors. Future uptake of influenza vaccination among healthcare workers may benefit from a fully transparent guideline process by a panel representing all relevant stakeholders, which clearly communicates the underlying rationale, evidence base and judgements made.

Understanding healthcare worker uptake of influenza vaccination: a survey

he growing threat of pandemic influenza highlights the importance of influenza vaccination as a public health measure. Yet despite the many benefits associated with influenza vaccination, national uptake by healthcare workers has remained low since being introduced for such staff in 2000. Improving uptake of influenza vaccination in healthcare workers has potential health benefits for individuals in terms of protection against the disease. Other possible benefits include a reduction in risk of nosocomial transmission to patient populations, improved public health for the population as a whole along with more efficient use of healthcare resources within the NHS. This research explored factors influencing influenza vaccination uptake in healthcare workers, by investigating knowledge, attitudes and behaviour of qualified nursing staff directly involved in patient care in NHS Lanarkshire. Differences in knowledge, attitudes and behaviours towards influenza vaccination were found across the targeted population. Such findings have the potential to inform and enhance the design and implementation of upcoming vaccination campaigns.

Prevention of Nosocomial Influenza

Objective:

To study compliance with preventive strategies at a university hospital during an outbreak of nosocomial influenza A during the winter of 1988, and the rates of vaccination of healthcare workers and of nosocomial influenza following changes in vaccine practices after the outbreak.

Design:

Retrospective review of employee health, hospital epidemiology, hospital computing, and clinical microbiology records.

Setting:

A university hospital.

Interventions:

Unvaccinated personnel with exposure within the previous 72 hours to an unisolated case of influenza were offered influenza vaccine and 14 days of amantadine hydrochloride prophylaxis. Personnel with exposure more than 72 hours before evaluation were offered vaccine. A mobile cart was introduced for vaccinating personnel after the 1988 outbreak.

Results:

An outbreak of influenza with 10 nosocomial cases occurred in 1988. Only 4% of exposed employees had been vaccinated previously and 23% of exposed, unvaccinated employees agreed to take vaccine, amantadine, or both. A mobile-cart vaccination program was instituted, and annual vaccination rates steadily increased from 26.3% in 1989 to 1990 to 38% in 1993 to 1994 (P<.0001). The relative frequency of documented cases of influenza in employees with symptoms of influenza decreased significantly during this period (P=.025), but nosocomial influenza rates among patients did not change significantly.

Conclusion:

A mobile-cart influenza vaccination program was associated with a significant increase in compliance among healthcare workers, but a majority still remained unvaccinated. The rate of nosocomial influenza among patients was not reduced by the modest increase in the vaccination rate, but influenza rates remained acceptably low, perhaps due to respiratory isolation of patients and furlough of employees with influenza.

Use of, Effectiveness of, and Attitudes Regarding Influenza Vaccine Among House Staff

Objective:

To determine influenza vaccination rates, vaccine effectiveness, and factors influencing vaccination decisions among house staff.

Design:

Cross-sectional survey.

Setting and Participants:

All residents registered at the University of Toronto were surveyed after the 1999-2000 influenza season. Of the 1,159 questionnaires mailed, 670 (58%) could be evaluated.

Results:

Influenza-like illnesses were reported by 36% of house staff. The vaccination rate was 51% among respondents, being highest for community and occupational medicine and pediatric staff (77% and 75%) and lowest for psychiatry, surgery, and radiology staff (32%, 36%, and 36%). Vaccinees reported significantly fewer episodes of illness (42 vs 54 per 100 subjects; P = .03) and fewer days of illness (272 vs 374 per 100 subjects; P = .02); absenteeism was not different (63 vs 69 per 100 subjects; P = .69). Self-protection was the most common reason for vaccination. Vaccinees believed the vaccine was more effective than did non-vaccinees (P < .01). Non-vaccinees considered influenza-like symptoms the most important side effect of the vaccine. Busy schedules and inconvenience were the most common reasons for not getting vaccinated. Overall, 44% of house staff believed the influenza vaccine should be mandatory.

Conclusions:

Influenza-like illness was common among house staff. They tended to work through their illnesses, potentially putting patients at risk. They were motivated mostly by self-protection and did report a benefit. Despite busy schedules and an unfounded fear of getting influenza symptoms from the vaccine, many thought the vaccine should be mandatory.

Visualizing knowledge and attitude factors related to influenza vaccination of physicians

PURPOSE

To characterize groups of primary healthcare physicians according to sociodemographic data, years of professional experience and knowledge of and attitudes to influenza, and to evaluate differences between groups with respect to influenza vaccination in the 2011-2012 season.

METHODS

We carried out an anonymous web survey of Spanish primary healthcare physicians in 2012. Information on vaccination, and knowledge of and attitudes to influenza was collected. Multiple correspondence analysis and cluster analysis were used to define groups of physicians.

RESULTS

We included 835 physicians and identified three types. Type B were physicians with low professional experience of influenza. Types A and C were physicians with high professional experience with influenza, type A also had a high awareness of influenza and seasonal vaccination. Types A and C were older and more often male than type B (p<0.0001). Knowledge of influenza was greatest in type A and lowest in type B. Awareness of influenza was greatest in type A and lowest in type C. In type A, 71.0% of physicians were vaccinated in the 2011-2012 season, compared with 48.1% and 33.6% from types B and C, respectively (p<0.001).

CONCLUSIONS

Additional efforts should be made to increase interest and concerns about preventing the transmission of influenza in physicians who do not believe influenza is a severe disease and are not concerned about its transmission.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced worldwide. Vaccination of pregnant women is recommended internationally, while healthy adults are targeted in North America.

OBJECTIVES

To identify, retrieve and assess all studies evaluating the effects (efficacy, effectiveness and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 2), MEDLINE (January 1966 to May 2013) and EMBASE (1990 to May 2013).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. We also included comparative studies assessing serious and rare harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 90 reports containing 116 data sets; among these 69 were clinical trials of over 70,000 people, 27 were comparative cohort studies (about eight million people) and 20 were case-control studies (nearly 25,000 people). We retrieved 23 reports of the effectiveness and safety of vaccine administration in pregnant women (about 1.6 million mother-child couples).The overall effectiveness of parenteral inactivated vaccine against influenza-like illness (ILI) is limited, corresponding to a number needed to vaccinate (NNV) of 40 (95% confidence interval (CI) 26 to 128). The overall efficacy of inactivated vaccines in preventing confirmed influenza has a NNV of 71 (95% CI 64 to 80). The difference between these two values depends on the different incidence of ILI and confirmed influenza among the study populations: 15.6% of unvaccinated participants versus 9.9% of vaccinated participants developed ILI symptoms, whilst only 2.4% and 1.1%, respectively, developed laboratory-confirmed influenza.No RCTs assessing vaccination in pregnant women were found. The only evidence available comes from observational studies with modest methodological quality. On this basis, vaccination shows very limited effects: NNV 92 (95% CI 63 to 201) against ILI in pregnant women and NNV 27 (95% CI 18 to 185) against laboratory-confirmed influenza in newborns from vaccinated women.Live aerosol vaccines have an overall effectiveness corresponding to a NNV 46 (95% CI 29 to 115).The performance of one-dose or two-dose whole virion pandemic vaccines was higher, showing a NNV of 16 (95% CI 14 to 20) against ILI and a NNV of 35 (95% CI 33 to 47) against influenza, while a limited impact on hospitalisation was found (NNV 94, 95% CI 70 to 1022).Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates. Inactivated vaccines caused local harms. No evidence of association with serious adverse events was found, but the harms evidence base was limited.The overall risk of bias in the included trials is unclear because it was not possible to assess the real impact of bias.

AUTHORS' CONCLUSIONS

Influenza vaccines have a very modest effect in reducing influenza symptoms and working days lost in the general population, including pregnant women. No evidence of association between influenza vaccination and serious adverse events was found in the comparative studies considered in the review. This review includes 90 studies, 24 of which (26.7%) were funded totally or partially by industry. Out of the 48 RCTs, 17 were industry-funded (35.4%).

What, in Fact, Is the Evidence That Vaccinating Healthcare Workers against Seasonal Influenza Protects Their Patients? A Critical Review

Background and Methods. Vaccination of all healthcare workers is widely recommended by health authorities and medical institutions and support for mandatory vaccination is increasing. This paper presents the relevant literature and examines the evidence for patient benefit from healthcare worker vaccination. Articles identified by Medline searches and citation lists were inspected for internal and external validity. Emphasis was put on RCTs. The literature on self-protection from vaccination is also presented. Results. Published research shows that personal benefit from vaccinating healthy nonelderly adults is small and there is no evidence that it is any different for HCWs. The studies aiming to prove the widespread belief that healthcare worker vaccination decreases patient morbidity and mortality are heavily flawed and the recommendations for vaccination biased. No reliable published evidence shows that healthcare workers' vaccination has substantial benefit for their patients-not in reducing patient morbidity or mortality and not even in increasing patient vaccination rates. Conclusion. The arguments for uniform healthcare worker influenza vaccination are not supported by existing literature. The decision whether to get vaccinated should, except possibly in extreme situations, be that of the individual healthcare worker, without legal, institutional, or peer coercion.

Effectiveness of seasonal influenza vaccination in healthcare workers: a systematic review

Vaccination is considered a key measure to protect vulnerable groups against influenza infection. The objectives of this review are to determine the effect of influenza vaccinations in reducing laboratory-confirmed influenza infections, influenza-like illnesses (ILIs), working days lost among vaccinated HCWs, and associated adverse effects after vaccination. Twenty-two healthcare-related databases and internet resources, as well as reference lists, and the bibliographies of all of the retrieved articles were examined. All randomized controlled trials (RCTs) comparing the effectiveness of any kind of influenza vaccine among all groups of HCWs with a placebo/vaccine other than the influenza vaccine/no intervention were included in the review. Only three RCTs matched the inclusion criteria. There is a limited amount of evidence suggesting that receiving influenza vaccination reduces laboratory-confirmed influenza infections in HCWs. No evidence can be found of influenza vaccinations significantly reducing the incidence of influenza, number of ILI episodes, days with ILI symptoms, or amount of sick leave taken among vaccinated HCWs. There is insufficient data to assess the adverse effects after vaccination. There is no definitive conclusion on the effectiveness of influenza vaccinations in HCWs because of the limited number of related trials. Further research is necessary to evaluate whether annual vaccination is a key measure to protect HCWs against influenza infection and thus increase their confidence in the vaccine. In the mean time, the direction of promoting influenza vaccination to HCWs can be shifted from staff protection to patient protection, with accurate information to address concerns and misconceptions.

How to develop a program to increase influenza vaccine uptake among workers in health care settings?

Background

Apart from direct protection and reduced productivity loss during epidemics, the main reason to immunize healthcare workers (HCWs) against influenza is to provide indirect protection of frail patients through reduced transmission in healthcare settings. Because the vaccine uptake among HCWs remains far below the health objectives, systematic programs are needed to take full advantage of such vaccination. In an earlier report, we showed a mean 9% increase of vaccine uptake among HCWs in nursing homes that implemented a systematic program compared with control homes, with higher rates in those homes that implemented more program elements. Here, we report in detail the process of the development of the implementation program to enable researchers and practitioners to develop intervention programs tailored to their setting.

Methods

We applied the intervention mapping (IM) method to develop a theory- and evidence-based intervention program to change vaccination behaviour among HCWs in nursing homes.

Results

After a comprehensive needs assessment, we were able to specify proximal program objectives and selected methods and strategies for inducing behavioural change. By consensus, we decided on planning of three main program components, i.e., an outreach visit to all nursing homes, plenary information meetings, and the appointment of a program coordinator -- preferably a physician -- in each home. Finally, we planned program adoption, implementation, and evaluation.

Conclusion

The IM methodology resulted in a systematic, comprehensive, and transparent procedure of program development. A potentially effective intervention program to change influenza vaccination behaviour among HCWs was developed, and its impact was assessed in a clustered randomised controlled trial.

An appraisal of the evidence underlying performance measures for community-acquired pneumonia

Numerous organizations use performance measures to monitor the quality of care provided for a variety of clinical conditions. An appraisal of the evidence underlying such performance measures has never been reported. Our objective was to estimate the effects of interventions recommended by performance measures and to determine the quality of evidence from which those estimates derive, using the Joint Commission and the Centers for Medicare and Medicaid Services' performance measures for community-acquired pneumonia (CAP) as examples. We performed systematic reviews of the literature to identify evidence related to the performance measures for CAP. Metaanalyses were then performed to estimate the absolute and relative effects of the interventions recommended by the performance measures. The Grading Recommendations, Assessment, Development, and Evaluation system was used to determine the quality of evidence. The estimated effects favored the interventions recommended by five of the six performance measures. These included pneumococcal vaccination (incidence of pneumococcal pneumonia: relative risk [RR], 0.43; 95% confidence interval [CI], 0.24-0.75), blood cultures, antibiotic administration within 6 hours, use of a guideline-compliant antibiotic regimen, and influenza vaccination (incidence of symptomatic influenza: RR, 0.30; 95% CI, 0.22-0.40). However, among these performance measures, only influenza vaccination was supported by high-quality evidence. One-step smoking cessation counseling was contradicted by moderate-quality evidence (smoking quit rate: RR, 1.05; 95% CI, 0.90-1.22). The evidence supporting performance measures is frequently not of high quality and occasionally contradictory.

High vaccination rates for seasonal and pandemic (A/H1N1) influenza among healthcare workers in Dutch general practice

In previous years, the influenza vaccination rate among Dutch general practitioners (GPs) was low (36% during the 2007/2008 season). Since 2008, yearly influenza vaccination has been actively recommended for GPs in The Netherlands. Moreover, in 2009 the Dutch government urged healthcare workers to receive additional vaccination against the pandemic influenza (A/H1N1). The effects of these recommendations are unknown. In February 2010, a questionnaire was mailed to random samples of GPs (n=810) and GP-trainees (n=300). Vaccination rates were determined and motives and barriers for vaccination were assessed. The response rates for GPs and GP-trainees were 83% and 90%, respectively. In total, 63% of the GPs were vaccinated against seasonal influenza and 85% against pandemic (A/H1N1) influenza. For GP-trainees, these percentages were 47% and 77%, respectively. With regard to the medical staff working in the respondents' practices, 60% received the seasonal and 76% the pandemic (A/H1N1) influenza vaccine. Reducing the risk of transmitting the virus to vulnerable patients and the individual's personal protection were the most frequently reported motives for vaccination. Having no medical indication for influenza vaccination and the conviction of being protected against influenza because of frequent professional exposure to the virus were the most frequently mentioned reasons for not being vaccinated. In conclusion, the seasonal influenza vaccination rate among Dutch GPs has risen considerably since the previous survey and the vaccination rate against pandemic (A/H1N1) influenza was very high. Moreover, Dutch GPs were convinced that influenza vaccination will reduce the risk of transmitting the virus to their patients.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced worldwide. Healthy adults are presently targeted mainly in North America.

OBJECTIVES

Identify, retrieve and assess all studies evaluating the effects of vaccines against influenza in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2010, issue 2), MEDLINE (January 1966 to June 2010) and EMBASE (1990 to June 2010).

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally-occurring influenza in healthy individuals aged 16 to 65 years. We also included comparative studies assessing serious and rare harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

We included 50 reports. Forty (59 sub-studies) were clinical trials of over 70,000 people. Eight were comparative non-RCTs and assessed serious harms. Two were reports of harms which could not be introduced in the data analysis. In the relatively uncommon circumstance of vaccine matching the viral circulating strain and high circulation, 4% of unvaccinated people versus 1% of vaccinated people developed influenza symptoms (risk difference (RD) 3%, 95% confidence interval (CI) 2% to 5%). The corresponding figures for poor vaccine matching were 2% and 1% (RD 1, 95% CI 0% to 3%). These differences were not likely to be due to chance. Vaccination had a modest effect on time off work and had no effect on hospital admissions or complication rates. Inactivated vaccines caused local harms and an estimated 1.6 additional cases of Guillain-Barré Syndrome per million vaccinations. The harms evidence base is limited.

AUTHORS' CONCLUSIONS

Influenza vaccines have a modest effect in reducing influenza symptoms and working days lost. There is no evidence that they affect complications, such as pneumonia, or transmission.WARNING: This review includes 15 out of 36 trials funded by industry (four had no funding declaration). An earlier systematic review of 274 influenza vaccine studies published up to 2007 found industry funded studies were published in more prestigious journals and cited more than other studies independently from methodological quality and size. Studies funded from public sources were significantly less likely to report conclusions favorable to the vaccines. The review showed that reliable evidence on influenza vaccines is thin but there is evidence of widespread manipulation of conclusions and spurious notoriety of the studies. The content and conclusions of this review should be interpreted in light of this finding.

Which determinants should be targeted to increase influenza vaccination uptake among health care workers in nursing homes?

Although health care workers (HCWs) have been recommended to be immunized against influenza, vaccine uptake remains low. So far, research on determinants of influenza vaccination among HCWs has been limited by design, population or theoretical framework. Therefore we conducted a questionnaire study in Dutch nursing homes to assess which demographical, behavioural and organisational determinants were associated with influenza vaccine uptake among HCWs. We were able to accurately predict vaccine uptake based on a 13-item prediction model including two demographical, nine behavioural and two organisational determinants developed with data from 1,125 respondents (response rate 60%). To further increase influenza vaccine uptake, implementation programs should target these determinants.

On the use of hemagglutination-inhibition for influenza surveillance: surveillance data are predictive of influenza vaccine effectiveness

The hemagglutination-inhibition (HI) assay is the main tool used by epidemiologists to quantify antigenic differences between circulating influenza virus strains, with the goal of selecting suitable vaccine strains. However, such quantitative measures of antigenic difference were recently shown to have poor predictive accuracy with respect to influenza vaccine effectiveness (VE) in healthy adults. Here, we re-examine those results using a more rigorous criterion for predictive accuracy -- considering only cases when the vaccine (V) and dominant (D) circulating strains are antigenically different -- and greater numbers of HI titers. We find that the Archetti -- Horsfall measure of antigenic difference, which is based on both the normalized HI titer (NHI) of D relative to antisera raised against V and the NHI of V relative to D, predicts VE very well (R(2)=0.62, p=4.1x10(-3)). In contrast, the predictive accuracies of the NHI of D relative to V alone (R(2)=0.01), and two other measures of antigenic difference based on the amino acid sequence of influenza virus hemagglutinin (R(2)=0.03 for both measures) are relatively poor. Furthermore, while VE in the elderly is generally high in cases when D and V are antigenically identical (VE=35%, S.E.=5%), in other cases VE appears to increase with the antigenic difference between D and V (R(2)=0.90, p=2.5x10(-5)). This paradoxical observation could reflect the confounding effects of prior immunity on estimates of VE in the elderly. Together, our results underscore the need for consistently accurate selection of suitable vaccine strains. We suggest directions for further studies aimed at improving vaccine-strain selection and present a large collection of HI titers that will be useful to such studies.

Willingness of healthcare workers to accept voluntary stockpiled H5N1 vaccine in advance of pandemic activity

Healthcare workers may be at risk during the next influenza pandemic. Priming with stockpiled vaccine may protect staff and reduce nosocomial transmission. Despite campaigns to increase seasonal influenza vaccine coverage, uptake among healthcare workers is generally low; creating uncertainty whether they would participate in pre-pandemic vaccine programmes. We conducted a cross-sectional questionnaire survey of healthcare workers in a UK hospital during, and 6 months after, a period of media reporting of an H5N1 outbreak at a commercial UK poultry farm. A total of 520 questionnaires were returned, representing 20% of frontline workforce. More respondents indicated willingness to accept stockpiled H5N1 vaccine during the period of media attention than after (166/262, 63.4% vs. 134/258, 51.9%; p=0.009). Following multivariate analysis, factors associated with willingness to accept H5N1 vaccine included: previous seasonal vaccine (OR 6.2, 95% CI 3.0-12.8, p<0.0001), awareness of occupational seasonal vaccine campaigns (OR 2.2, 95% CI 1.4-3.5, p=0.001), belief that seasonal vaccine benefits themselves (OR 2.5, 95% CI 1.6-4.0, p<0.0001) or the hospital (OR 3.6, 95% CI 2.3-5.8, p<0.0001), belief that pandemic risk is high/moderate (OR 14.1, 95% CI 7.6-26.1, p<0.0001) and would threaten healthcare workers (OR 2.9, 95% CI 1.8-4.5, p<0.0001). Those who would not accept vaccine (220 respondents, 42.7%) if offered before the pandemic do not perceive pandemic influenza as a serious threat, and have concerns regarding vaccine safety. A majority of healthcare workers are amenable to accept stockpiled H5N1 vaccine if offered in advance of pandemic activity.

Influenza immunization of Dutch general practitioners: vaccination rate and attitudes towards vaccination

With effect from the 2008/2009 season, yearly influenza immunization will be recommended to all Dutch general practitioners (GPs). For successful implementation of this recommendation, knowledge about the current vaccination rate and attitudes towards vaccination is necessary. In February 2008, a questionnaire was mailed to a random sample (n=730) of practicing GPs. Vaccination rate was determined and the factors associated with not being vaccinated were assessed using multivariate logistic regression. Reasons for being vaccinated or not were also recorded. Of the 730 questionnaires sent out, 698 (96%) were completed and returned. In total, 248 GPs (36%) had been immunized against influenza. Independent factors related to not being vaccinated were female gender and age <40 years. Having no medical indication for an influenza vaccination and the conviction that one is protected against influenza because of frequent professional exposure to the virus were the most frequently reported reasons for not being vaccinated. The most frequently reported motives for being vaccinated were personal protection against influenza and a lower risk of transmitting the virus to patients. Education of GPs about the effects of vaccination may be needed to ensure their compliance to the current recommendation of yearly influenza immunization.

Does vaccinating ED health care workers against influenza reduce sickness absenteeism?

This study aims to investigate the association between influenza vaccination of health care workers (HCWs) and sickness absenteeism. A retrospective cohort study was conducted in an emergency department (ED) of an acute care hospital. All full-time HCWs except physicians (73 nurses and health care attendants) were included. Influenza vaccine was administered to HCWs on a voluntary basis commencing November 2004. Absenteeism due to influenza-like illness during the period from January to October 2005 was noted. The mean number of cumulative sick leave days per person was smaller (1.0 days against 1.75 days) in vaccine recipients than in vaccine nonrecipients although the difference was not statistically significant. A significantly larger proportion of subjects took sick leave because of influenza-like illness in the vaccine nonrecipient group (55% against 30.3%, P = .034).

CONCLUSION

Influenza vaccination of HCWs in the ED setting is significantly associated with a fewer number of HCWs requiring sick leave.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Different types of influenza vaccines are currently produced world-wide. Healthy adults are at present targeted only in North America. Despite the publication of a large number of clinical trials, there is still substantial uncertainty about the clinical effectiveness of influenza vaccines and this has a negative impact on their acceptance and uptake.

OBJECTIVES

To identify, retrieve and assess all studies evaluating the effects (efficacy, effectiveness and harms) of vaccines against influenza in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 4, 2005) which contains the Cochrane Acute Respiratory Infections Group trials register; MEDLINE (January 1966 to January 2006); and EMBASE (1990 to January 2006). We wrote to vaccine manufacturers and first or corresponding authors of studies in the review.

SELECTION CRITERIA

Any randomised or quasi-randomised studies comparing influenza vaccines in humans with placebo, no intervention. Live, attenuated, or killed vaccines or fractions of them administered by any route, irrespective of antigenic configuration were assessed. Only studies assessing protection from exposure to naturally occurring influenza in healthy individuals aged 16 to 65 years were considered. Comparative non-randomised studies were included if they assessed evidence of the possible association between influenza vaccines and serious harms.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data.

MAIN RESULTS

Forty-eight reports were included: 38 (57 sub-studies) were clinical trials providing data about effectiveness, efficacy and harms of influenza vaccines and involved 66,248 people; 8 were comparative non-randomised studies and tested the association of the vaccines with serious harms; 2 were reports of harms which could not be introduced in the data analysis. Inactivated parenteral vaccines were 30% effective (95% CI 17% to 41%) against influenza-like illness, and 80% (95% CI 56% to 91%) efficacious against influenza when the vaccine matched the circulating strain and circulation was high, but decreased to 50% (95% CI 27% to 65%) when it did not. Excluding the studies of the 1968 to 1969 pandemic, effectiveness was 15% (95% CI 9% to 22%) and efficacy was 73% (95% CI 53% to 84%). Vaccination had a modest effect on time off work, but there was insufficient evidence to draw conclusions on hospital admissions or complication rates. Inactivated vaccines caused local tenderness and soreness and erythema. Spray vaccines had more modest performance. Monovalent whole-virion vaccines matching circulating viruses had high efficacy (VE 93%, 95% CI 69% to 98%) and effectiveness (VE 66%, 95% CI 51% to 77%) against the 1968 to 1969 pandemic.

AUTHORS' CONCLUSIONS

Influenza vaccines are effective in reducing cases of influenza, especially when the content predicts accurately circulating types and circulation is high. However, they are less effective in reducing cases of influenza-like illness and have a modest impact on working days lost. There is insufficient evidence to assess their impact on complications. Whole-virion monovalent vaccines may perform best in a pandemic.

Effectiveness of influenza vaccination: A survey within the Italian Ministry of Health personnel

An initiative of active prevention, to promote an influenza vaccination programme, has been carried out in the Ministry of Health of Rome, Directorate General of Health Prevention: during October 2004 influenza vaccine has been actively offered to all the employees; 46 out of the 129 workers (about 36% of the total) accepted to be vaccinated. Afterward, the propensity to get influenza of the vaccinated has been compared with that of a control group, operating in the same setting, but not vaccinated. Taking into account that the groups in question is far too small, the statistical results showed that influenza vaccination of healthy working adults did not reduce the rates of influenza-like-illness (ILI), in addition, the difference between average duration of disease in unvaccinated persons was not statistically significant.

Influenza vaccination health impact and cost effectiveness among adults aged 50 to 64 and 65 and older

BACKGROUND

Influenza causes approximately 36,000 deaths per year in the United States despite the presence of an effective vaccine. This assessment of the value of influenza vaccination to the U.S. population is part of an update to the 2001 ranking of clinical preventive services recommended by the U.S. Preventive Services Task Force. The forthcoming ranking will include the new recommendation of the Advisory Committee on Immunization Practices to extend influenza vaccination to adults aged 50 to 64 years.

METHODS

This service is evaluated on the two most important dimensions: burden of disease prevented and cost effectiveness. Study methods, described in a companion article, are designed to ensure consistency across many services.

RESULTS

Over the lifetime of a birth cohort of 4 million, it is estimated that about 275,000 quality-adjusted life years (QALYs) would be saved if influenza vaccination were offered annually to all people after age 50. Eighty percent of the QALYs saved (220,000) would be achieved by offering the vaccine only to persons aged 65 and older. In year 2000 dollars, the cost effectiveness of influenza vaccination is $980 per QALY saved in persons aged 65 and older, and $28,000 per QALY saved in persons aged 50 to 64. When the costs of patient time and travel are excluded, the cost effectiveness ratio of vaccinating 50- to 64-year-olds decreases to $7200 per QALY saved, and vaccinating those aged 65 and older saves $17 per person vaccinated.

CONCLUSIONS

Influenza vaccination is a high-impact, cost-effective service for persons aged 65 and older. Vaccinations are also cost effective for persons aged 50 to 64.

Vaccination versus treatment of influenza in working adults: a cost-effectiveness analysis

PURPOSE

To determine the cost-effectiveness of influenza vaccination, antiviral therapy, or no intervention for healthy working adults, accounting for annual variation in vaccine efficacy.

METHODS

We conducted a cost-effectiveness analysis based on published clinical trials of influenza vaccine and antiviral drugs, incorporating 10 years of surveillance data from the World Health Organization. We modeled influenza vaccination, treatment of influenza-like illness with antiviral drugs, or both, as compared with no intervention, targeting healthy working adults under age 50 years in the general community or workplace. Outcomes included costs, illness days, and quality-adjusted days gained.

RESULTS

In the base case analysis, the majority of costs incurred for all strategies were related to lost productivity from influenza illness. The least expensive strategy varied from year to year. For the 10-year period, antiviral therapy without vaccination was associated with the lowest overall costs (234 US dollars per person per year). Annual vaccination cost was 239 US dollars per person, and was associated with 0.0409 quality-adjusted days saved, for a marginal cost-effectiveness ratio of 113 US dollars per quality-adjusted day gained or 41,000 US dollars per quality-adjusted life-year saved compared with antiviral therapy. No intervention was the most expensive and least effective option. In sensitivity analyses, lower vaccination costs, higher annual probabilities of influenza, and higher numbers of workdays lost to influenza made vaccination more cost-effective than treatment. If vaccination cost was less than 16 US dollars or time lost from work exceeded 2.4 days per episode of influenza, then vaccination was cost saving compared with all other strategies.

CONCLUSION

Influenza vaccination for healthy working adults is reasonable economically, and under certain circumstances is cost saving. Antiviral therapy is consistently cost saving.

Methodological quality of studies and patient age as major sources of variation in efficacy estimates of influenza vaccination in healthy adults: a meta-analysis

A meta-analysis of randomized and quasi-randomized control trials evaluating influenza vaccination efficacy in healthy adults was carried out to investigate potential sources of heterogeneity among the published studies. The pooled estimates of vaccine efficacy were 22% (95% CI = 16-28) for preventing clinically diagnosed cases of influenza and 63% (95% CI = 53-71) for preventing laboratory confirmed cases of influenza. These estimates are likely to vary substantially according to the age of the subjects, with vaccine efficacy decreasing significantly with the increase of the mean age of the patients, and to the methodological quality of trials, with low quality trials associated with an overestimation of influenza vaccine efficacy. Some evidence of publication bias was found, particularly when the outcome assessed was clinically diagnosed influenza. Further high-quality clinical trials, designed to facilitate future pooled analyses, are needed to provide definitive answers for policy-makers.

Vaccines for preventing influenza in healthy adults

BACKGROUND

Three different types of influenza vaccines are currently produced worldwide. None is traditionally targeted to healthy adults. Despite the publication of a large number of clinical trials, there is still substantial uncertainty about the clinical effectiveness of influenza vaccines and this has negative impact on the vaccines acceptance and uptake.

OBJECTIVES

To assess the effects of vaccines on influenza in healthy adults. To assess the effectiveness of vaccines in preventing cases of influenza in healthy adults. To estimate the frequency of adverse effects associated with influenza vaccination in healthy adults.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1, 2004) which contains the Cochrane Acute Respiratory Infections Group trials register; MEDLINE (January 1966 to December 2003); and EMBASE (1990 to December 2003). We wrote to vaccine manufacturers and first or corresponding authors of studies in the review.

SELECTION CRITERIA

Any randomised or quasi-randomised studies comparing influenza vaccines in humans with placebo, control vaccines or no intervention, or comparing types, doses or schedules of influenza vaccine. Live, attenuated or killed vaccines or fractions thereof administered by any route, irrespective of antigenic configuration were considered. Only studies assessing protection from exposure to naturally occurring influenza in healthy individuals aged 14 to 60 (irrespective of influenza immune status) were considered.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Twenty five reports of studies involving 59,566 people were included. The recommended live aerosol vaccines reduced the number of cases of serologically confirmed influenza by 48% (95% confidence interval (CI) 24% to 64%), whilst recommended inactivated parenteral vaccines had a vaccine efficacy of 70% (95% CI 56% to 80%). The yearly recommended vaccines had low effectiveness against clinical influenza cases: 15%(95% CI 8% to 21%) and 25% (95% CI 13% to 35%) respectively. Overall the percentage of participants experiencing clinical influenza decreased by 6%. Use of the vaccine significantly reduced time off work but only by 0.16 days for each influenza episode (95% CI 0.04 to 0.29 days); Analysis of vaccines matching the circulating strain gave higher estimates of efficacy, whilst inclusion of all other vaccines reduced the efficacy.

REVIEWERS' CONCLUSIONS

Influenza vaccines are effective in reducing serologically confirmed cases of influenza. However, they are not as effective in reducing cases of clinical influenza and number of working days lost. Universal immunisation of healthy adults is not supported by the results of this review.

A prospective, Internet-based study of the effectiveness and safety of influenza vaccination in the 2001–2002 influenza season

The effectiveness of the influenza vaccine used in the 2001-2002 influenza season in Japan was investigated in a large-scale, geographically widely distributed, Internet-based study. Data were collected from 8841 of 9902 subjects registered by 38 clinics prior to the start of influenza season. Subjects were categorized into three groups by vaccination regimen: unvaccinated, vaccinated once, and vaccinated twice. Efficacy was also analyzed for three age groups: 0-15, 16-64, and 65-104 years. Influenza-like illness (ILI) was diagnosed according to Ministry of Health (MWH, Labor and Welfare in Japan) criteria. Laboratory-confirmed influenza cases were analyzed separately. The respective vaccine efficacy in the 0-15 years group for the one- and two-dose regimens was 67.6 and 84.5% for ILI and 54.0 and 79.8% for laboratory-confirmed influenza. Influenza vaccination was also shown to be effective in subjects 16-64 years. Vaccine effectiveness was not able to be determined for the over 65 years group, probably due to an insufficient number of infected patients. These results suggest that influenza vaccination is effective for children and adults and that a two-dose regimen is superior to a single dose in children 0-15 years.

A Markov model for sample size calculation and inference in vaccine cost-effectiveness studies

Sample size and power formulae are derived for designing trials of vaccine cost-effectiveness in healthy working adults. When existing trials of influenza vaccine have presented sample size calculations, these have been based on vaccine effectiveness. A Markov model is introduced to account for non-independence of working days lost. Two effect sizes need to be specified, one for a reduction in the number of episodes of absence and the second for a reduction in the mean duration of episodes. The relative cost of vaccine provision is also incorporated. Applying the resulting formulae to published studies indicates that most were underpowered to detect any financial benefit. Moreover, biased estimates of variance have led to led to incorrect inference.

Influenza: New Insights Into an Old Disease

In the United States each year, influenza accounts for an estimated 20,000 to 40,000 deaths, nearly 300,000 hospitalizations, and millions of days lost from work. In the past few years, there has been an explosion of information in the medical literature related to influenza. This paper reviews these latest developments that enhance our understanding of influenza epidemiology and virology and expand our prevention and treatment options. Diminishing the impact of influenza in this country will require continued intense surveillance, increased use of influenza vaccine, and the availability of alternative vaccines and antivirals with the potential for broader protection against shift-and-drift strains of influenza.

Randomized, placebo-controlled double blind study on the efficacy of influenza immunization on absenteeism of health care workers

BACKGROUND

In healthy adults influenza immunization reduces absenteeism caused by respiratory infections, but data on its efficacy among health care workers are scarce.

OBJECTIVE

To determine the effect of the conventional inactivated influenza A vaccine on reducing absenteeism related to respiratory infections among pediatric health care providers.

STUDY DESIGN

A randomized, placebo-controlled, double blind study on vaccine efficacy was conducted in two pediatric hospitals during the winter season 1996 to 1997. The primary endpoint was days of work lost from the hospital because of respiratory infections. The documentation of absenteeism was based on personal sickness logs.

RESULTS

Of the 547 randomized vaccinees 427 (78%) persons completed the 4-month follow-up and returned the sickness logs. Immunization failed to reduce episodes of respiratory infections (1.8 episodes/study period among vaccinees vs. 2.0 among controls). Similarly the vaccine failed to affect the total number of days the vaccinees suffered from respiratory infections (13.5 days vs. 14.6 days, respectively). However, days of work lost because of respiratory infections (1.0 days vs. 1.4 days, respectively, P = 0.02) and especially total numbers of days the study persons felt themselves unable to work when either on or off duty (2.5 days vs. 3.5 days, P 0.02) were significantly decreased.

CONCLUSION

Influenza vaccination reduced absenteeism related to respiratory infections by 28%. We therefore believe that routine annual influenza immunizations should be recommended to health care providers working in pediatric settings.

Cost-effectiveness of the influenza vaccine in a healthy, working-age population

To determine if the influenza vaccine can reduce absenteeism and the cost of Influenza-Like Illness (ILI) in healthy adults in the workplace, a prospective, non-randomized, non-placebo control trial was done in six North Carolina textile plants. One hundred thirty-one vaccinated employees were compared with 131 age- and gender-matched non-vaccines from different plants. Twenty-six (20%) of the vaccinated and 64 (49%) of the unvaccinated group had ILI (P = 0.0000008). Fifteen (11%) of the vaccinated and 31 (24%) of the unvaccinated employees missed work because of ILI (P = 0.01). There were 43 lost workdays in vaccinated and 93 in unvaccinated employees (P = 0.00004). The "cost per saved lost workday" was $22.36, for a company savings of $2.58 per dollar invested in the vaccination program. We concluded that the influenza vaccine can give significant reductions in incidence, absenteeism, and cost associated with ILJ in the workplace.