Two outbreaks of influenza A (H3N2) in a Japanese nursing home in the winter of 1996-1997, with differing vaccine efficacy

Vaccines for preventing influenza in the elderly

BACKGROUND

The consequences of influenza in the elderly (those age 65 years or older) are complications, hospitalisations, and death. The primary goal of influenza vaccination in the elderly is to reduce the risk of death among people who are most vulnerable. This is an update of a review published in 2010. 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 because of their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in the elderly.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 11), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register; MEDLINE (1966 to 31 December 2016); Embase (1974 to 31 December 2016); Web of Science (1974 to 31 December 2016); CINAHL (1981 to 31 December 2016); LILACS (1982 to 31 December 2016); WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017); and ClinicalTrials.gov (1 July 2017).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs assessing efficacy against influenza (laboratory-confirmed cases) or effectiveness against influenza-like illness (ILI) or safety. We considered any influenza vaccine given independently, in any dose, preparation, or time schedule, compared with placebo or with no intervention. Previous versions of this review included 67 cohort and case-control studies. The searches for these trial designs are no longer updated.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed risk of bias and extracted data. We rated the certainty of evidence with GRADE for the key outcomes of influenza, ILI, complications (hospitalisation, pneumonia), and adverse events. We have presented aggregate control group risks to illustrate the effect in absolute terms. We used them as the basis for calculating the number needed to vaccinate to prevent one case of each event for influenza and ILI outcomes.

MAIN RESULTS

We identified eight RCTs (over 5000 participants), of which four assessed harms. The studies were conducted in community and residential care settings in Europe and the USA between 1965 and 2000. Risk of bias reduced our certainty in the findings for influenza and ILI, but not for other outcomes.Older adults receiving the influenza vaccine may experience less influenza over a single season compared with placebo, from 6% to 2.4% (risk ratio (RR) 0.42, 95% confidence interval (CI) 0.27 to 0.66; low-certainty evidence). We rated the evidence as low certainty due to uncertainty over how influenza was diagnosed. Older adults probably experience less ILI compared with those who do not receive a vaccination over the course of a single influenza season (3.5% versus 6%; RR 0.59, 95% CI 0.47 to 0.73; moderate-certainty evidence). These results indicate that 30 people would need to be vaccinated to prevent one person experiencing influenza, and 42 would need to be vaccinated to prevent one person having an ILI.The study providing data for mortality and pneumonia was underpowered to detect differences in these outcomes. There were 3 deaths from 522 participants in the vaccination arm and 1 death from 177 participants in the placebo arm, providing very low-certainty evidence for the effect on mortality (RR 1.02, 95% CI 0.11 to 9.72). No cases of pneumonia occurred in one study that reported this outcome (very low-certainty evidence). No data on hospitalisations were reported. Confidence intervaIs around the effect of vaccines on fever and nausea were wide, and we do not have enough information about these harms in older people (fever: 1.6% with placebo compared with 2.5% after vaccination (RR 1.57, 0.92 to 2.71; moderate-certainty evidence)); nausea (2.4% with placebo compared with 4.2% after vaccination (RR 1.75, 95% CI 0.74 to 4.12; low-certainty evidence)).

AUTHORS' CONCLUSIONS

Older adults receiving the influenza vaccine may have a lower risk of influenza (from 6% to 2.4%), and probably have a lower risk of ILI compared with those who do not receive a vaccination over the course of a single influenza season (from 6% to 3.5%). We are uncertain how big a difference these vaccines will make across different seasons. Very few deaths occurred, and no data on hospitalisation were reported. No cases of pneumonia occurred in one study that reported this outcome. We do not have enough information to assess harms relating to fever and nausea in this population.The evidence for a lower risk of influenza and ILI with vaccination is limited by biases in the design or conduct of the studies. Lack of detail regarding the methods used to confirm the diagnosis of influenza limits the applicability of this result. The available evidence relating to complications is of poor quality, insufficient, or old and provides no clear guidance for public health regarding the safety, efficacy, or effectiveness of influenza vaccines for people aged 65 years or older. Society should invest in research on a new generation of influenza vaccines for the elderly.

Influenza outbreak control practices and the effectiveness of interventions in long-term care facilities: a systematic review

Background

Evaluation of influenza control measures frequently focuses on the efficacy of chemoprophylaxis and vaccination, while the effectiveness of non-pharmaceutical interventions (NPI) receives less emphasis. While influenza control measures are frequently reported for individual outbreaks, there have been few efforts to characterize the real-world effectiveness of these interventions across outbreaks.

Objectives

To characterize influenza case and outbreak definitions and control measures reported by long-term care facilities (LTCFs) of elderly adults and estimate the reduction in influenza-like illness (ILI) attack rates due to chemoprophylaxis and NPI.

Methods

We conducted a literature search in PubMed including English-language studies reporting influenza outbreaks among elderly individuals in LTCFs. A Bayesian hierarchical logistic regression model estimated the effects of control measures on ILI attack rates.

Results

Of 654 articles identified in the literature review, 37 articles describing 60 influenza outbreaks met the inclusion criteria. Individuals in facilities where chemoprophylaxis was used were significantly less likely to develop influenza A or B than those in facilities with no interventions [odds ratio (OR) 0·48, 95% CI: 0·28, 0·84]. Considered by drug class, adamantanes significantly reduced infection risk (OR 0·22, 95% CI: 0·12, 0·42), while neuraminidase inhibitors did not show a significant effect. Although NPI showed no significant effect, the results suggest that personal protective equipment may produce modest protective effects.

Conclusions

Our results indicate pharmaceutical control measures have the clearest reported protective effect in LTCFs. Non-pharmaceutical approaches may be useful; however, most data were from observational studies and standardized reporting or well-conducted clinical trials of NPI are needed to more precisely measure these effects.

Implementing an influenza vaccination programme for adults aged ≥65 years in Poland: a cost-effectiveness analysis

BACKGROUND AND OBJECTIVES

Influenza is a common respiratory disease occurring in seasonal patterns, and may lead to severe complications in frail populations such as the elderly. In Poland, influenza vaccination is recommended for people aged ≥65 years; however the vaccine coverage rate in the elderly is very low. The fact that influenza vaccine is neither reimbursed by the National Health Insurance (Narodowy Fundusz Zdrowia [NFZ]) nor financed via a National Immunization Program (NIP) could be a reason for the low coverage rate. This study assessed the cost effectiveness of the full reimbursement of an influenza vaccination programme in Poland for people aged ≥65 years.

METHODS

A decision-analytic model was developed to compare costs and outcomes associated with the current situation in which influenza vaccination is not reimbursed and a new situation in which it would be fully covered by the NFZ. The model was parameterized to Poland using data from the literature and from the Central Statistic Office of Poland. Within the elderly population, 50% were considered to be at high risk of influenza complications. An influenza attack rate of 3.5% was used for calculation purposes. Influenza-associated hospitalizations and death rates were estimated at 439.9 per 100 000 person-years and 79.1 per 100 000 person-years, respectively. Cost estimates were derived from a cost study conducted in Poland. Costs are presented in Polish Zloty (PLN) [2009 mean exchange rate: 1 PLN = €0.232]. Only direct medical costs were included to fit to the NFZ perspective. To reflect the seasonality of influenza, a time horizon of 1 year was chosen. Life-years and quality-adjusted life-years (QALYs) accumulated over future years were discounted at a rate of 5% as recommended by Polish guidelines. Deterministic and probabilistic sensitivity analyses were conducted.

RESULTS

In Poland, the introduction of the public funding of influenza vaccination for people aged ≥65 years would cost PLN 79 million when an increase in coverage rate from 13.5% to 40% is assumed. 23 900 cases of influenza, 1777 hospitalizations and 548 premature deaths would be averted each year due to the influenza vaccination programme. Fifty-seven persons would need to be vaccinated to prevent one case of influenza. To prevent one hospitalization and one death due to influenza, 842 and 2809 individuals would need to be vaccinated, respectively. The new strategy would be very cost effective compared with the current situation with an incremental cost-effectiveness ratio (ICER) of PLN26 118/QALY, which is below the 2009 yearly gross domestic product (GDP) per capita. Deterministic sensitivity analyses demonstrated that the most influential variables for the ICER were vaccine efficacy against death, excess hospitalization rate, utility norms, influenza attack rate, vaccine efficacy against hospitalization, and discount rates. All ICERs computed were below the threshold of 3 GDP per capita. From the probabilistic analysis, the proposed new influenza vaccination programme, if implemented, was predicted to be cost effective from the NFZ perspective with a probability of 100%, given the same threshold.

CONCLUSION

Implementing a vaccination programme in Poland in which influenza vaccination would be fully reimbursed by the NFZ for people aged ≥65 years would be a very cost-effective strategy.

[Flu vaccination in the elderly]

Seasonal flu is a very serious public health problem in the elderly due to its morbidity and mortality and financial and social costs arising from this. The aim of this review is to describe the magnitude and importance of seasonal flu in this population group, and its prevention by means of vaccination. For this reason, an updated account of the composition of the vaccine, its dosage and administration route, vaccine safety and the evaluation of the immunogenicity and effectiveness of vaccination. There is variation between different countries and official organisations on the age at which flu vaccination must be established in the elderly. New flu vaccination strategies need to be introduced, to further improve flu vaccination cover in Spain.

Vaccines for preventing influenza in the elderly

BACKGROUND

Vaccines have been the main global weapon to minimise the impact of influenza in the elderly for the last four decades and are recommended worldwide for individuals aged 65 years or older. The primary goal of influenza vaccination in the elderly is to reduce the risk of complications among persons who are most vulnerable.

OBJECTIVES

To assess the effectiveness of vaccines in preventing influenza, influenza-like illness (ILI), hospital admissions, complications and mortality in the elderly. To identify and appraise comparative studies evaluating the effects of influenza vaccines in the elderly. To document types and frequency of adverse effects associated with influenza vaccines in the elderly.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), which contains the Cochrane Acute Respiratory Infections (ARI) Group's Specialised Register (The Cochrane Library 2009, issue 4); MEDLINE (January 1966 to October Week 1 2009); EMBASE (1974 to October 2009) and Web of Science (1974 to October 2009).

SELECTION CRITERIA

Randomised controlled trials (RCTs), quasi-RCTs, cohort and case-control studies assessing efficacy against influenza (laboratory-confirmed cases) or effectiveness against influenza-like illness (ILI) or safety. Any influenza vaccine given independently, in any dose, preparation or time schedule, compared with placebo or with no intervention was considered.

DATA COLLECTION AND ANALYSIS

We grouped reports first according to the setting of the study (community or long-term care facilities) and then by level of viral circulation and vaccine matching. We further stratified by co-administration of pneumococcal polysaccharide vaccine (PPV) and by different types of influenza vaccines. We analysed the following outcomes: influenza, influenza-like illness, hospital admissions, complications and deaths.

MAIN RESULTS

We included 75 studies. Overall we identified 100 data sets. We identified one RCT assessing efficacy and effectiveness. Although this seemed to show an effect against influenza symptoms it was underpowered to detect any effect on complications (1348 participants). The remainder of our evidence base included non-RCTs. Due to the general low quality of non-RCTs and the likely presence of biases, which make interpretation of these data difficult and any firm conclusions potentially misleading, we were unable to reach clear conclusions about the effects of the vaccines in the elderly.

AUTHORS' CONCLUSIONS

The available evidence is of poor quality and provides no guidance regarding the safety, efficacy or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly-funded randomised, placebo-controlled trial run over several seasons should be undertaken.

Vaccines for preventing influenza in the elderly

BACKGROUND

Influenza vaccination of elderly individuals is recommended worldwide and has been targeted toward the elderly and those at serious risk of complications.

OBJECTIVES

Our aim was to review the evidence of efficacy, effectiveness and safety of influenza vaccines in individuals aged 65 years or older.

SEARCH STRATEGY

We searched the following databases on The Cochrane Library, the Cochrane Central Register of Controlled Trials (CENTRAL), the Cochrane Database of Systematic Reviews, and the Database of Abstracts of Reviews of Effectiveness (Issue 1, 2006); MEDLINE (January 1966 to March Week 3 2006); EMBASE (Dialog 1974 to 1979; SilverPlatter 1980 to December 2005); Biological Abstracts (SilverPlatter 1969 to December 2004); and Science Citation Index (Web of Science 1974 to December 2004).

SELECTION CRITERIA

We considered randomised, quasi-randomised, cohort and case-control studies assessing efficacy against influenza (laboratory-confirmed cases) or effectiveness against influenza-like illness (ILI) or safety. Any influenza vaccine given independently, in any dose, preparation or time schedule, compared with placebo or with no intervention was considered.

DATA COLLECTION AND ANALYSIS

We grouped reports first according to the setting of the study (community or long-term care facilities) and then by level of viral circulation and vaccine matching. We further stratified by co-administration of pneumococcal polysaccharide vaccine (PPV) and by different types of influenza vaccines. We analysed the following outcomes: influenza, influenza-like illness, hospital admissions, complications and deaths.

MAIN RESULTS

Sixty-four studies were included in the efficacy / effectiveness assessment, resulting in 96 data sets. In homes for elderly individuals (with good vaccine match and high viral circulation) the effectiveness of vaccines against ILI was 23% (6% to 36%) and non-significant against influenza (RR 1.04: 95% CI 0.43 to 2.51). We found no correlation between vaccine coverage and ILI attack rate. Well matched vaccines prevented pneumonia (VE 46%; 30% to 58%), hospital admission (VE 45%; 16% to 64%) and deaths from influenza or pneumonia (VE 42%, 17% to 59%). In elderly individuals living in the community, vaccines were not significantly effective against influenza (RR 0.19; 95% CI 0.02 to 2.01), ILI (RR 1.05: 95% CI 0.58 to 1.89), or pneumonia (RR 0.88; 95% CI 0.64 to 1.20). Well matched vaccines prevented hospital admission for influenza and pneumonia (VE 26%; 12% to 38%) and all-cause mortality (VE 42%; 24% to 55%). After adjustment for confounders, vaccine performance was improved for admissions to hospital for influenza or pneumonia (VE* 27%; 21% to 33%), respiratory diseases (VE* 22%; 15% to 28%) and cardiac disease (VE* 24%; 18% to 30%); and for all-cause mortality (VE* 47%; 39% to 54%). The public health safety profiles of the vaccines appear to be acceptable.

AUTHORS' CONCLUSIONS

In long-term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest. The apparent high effectiveness of the vaccines in preventing death from all causes may reflect a baseline imbalance in health status and other systematic differences in the two groups of participants.

Efficacy and effectiveness of influenza vaccines in elderly people: a systematic review

BACKGROUND

Influenza vaccination of elderly individuals is recommended worldwide. Our aim was to review the evidence of efficacy and effectiveness of influenza vaccines in individuals aged 65 years or older.

METHODS

We searched five electronic databases to December, 2004, in any language, for randomised (n=5), cohort (n=49), and case-control (n=10) studies, assessing efficacy against influenza (reduction in laboratory-confirmed cases) or effectiveness against influenza-like illness (reduction in symptomatic cases). We expressed vaccine efficacy or effectiveness as a proportion, using the formula VE=1-relative risk (RR) or VE*=1-odds ratio (OR). We analysed the following outcomes: influenza, influenza-like illness, hospital admissions, complications, and deaths.

FINDINGS

In homes for elderly individuals (with good vaccine match and high viral circulation) the effectiveness of vaccines against influenza-like illness was 23% (95% CI 6-36) and non-significant against influenza (RR 1.04, 0.43-2.51). Well matched vaccines prevented pneumonia (VE 46%, 30-58) and hospital admission (VE 45%, 16-64) for and deaths from influenza or pneumonia (VE 42%, 17-59), and reduced all-cause mortality (VE 60%, 23-79). In elderly individuals living in the community, vaccines were not significantly effective against influenza (RR 0.19, 0.02-2.01), influenza-like illness (RR 1.05, 0.58-1.89), or pneumonia (RR 0.88, 0.64-1.20). Well matched vaccines prevented hospital admission for influenza and pneumonia (VE 26%, 12-38) and all-cause mortality (VE 42%, 24-55). After adjustment for confounders, vaccine performance was improved for admissions to hospital for influenza or pneumonia (VE* 27%, 21-33), respiratory diseases (VE* 22%, 15-28), and cardiac disease (VE* 24%, 18-30), and for all-cause mortality (VE* 47%, 39-54).

INTERPRETATION

In long-term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest.

Influenza- and respiratory syncytial virus-associated morbidity and mortality in the nursing home population

OBJECTIVES

To estimate winter viral-related morbidity and mortality in Tennessee nursing home residents during 4 consecutive years.

DESIGN

A retrospective cohort study.

SETTING

Three hundred eighty-one Tennessee nursing homes.

PARTICIPANTS

Nursing home residents.

MEASUREMENTS

Viral surveillance data were used to define three seasons: influenza (influenza and respiratory syncytial virus (RSV) cocirculating), RSV (RSV alone circulating), and non winter-viral (neither virus circulating). Adjusted seasonal differences in rates of cardiopulmonary hospitalizations, antibiotic prescriptions, and deaths during these three seasons were calculated to estimate annual hospitalizations, courses of antibiotics, and deaths attributable to influenza and RSV from 1995 to 1999.

RESULTS

Nursing home residents had 81,885 person-years of follow-up. In the 63% of residents with comorbid conditions that increase influenza morbidity, influenza infection contributed to an estimated average of 28 hospitalizations, 147 courses of antibiotics, and 15 deaths per 1,000 persons annually. Similarly, RSV accounted for an annual average of 15 hospitalizations, 76 courses of antibiotics, and 17 deaths per 1,000 persons. Influenza and RSV accounted for 7% of cardiopulmonary hospitalizations and 9% of total deaths in high-risk residents during the 4 study years. Absolute morbidity and mortality were lower in residents without identified comorbid conditions but accounted for 15% of hospitalizations and 14% of deaths. These estimates depend on the assumption that morbidity and mortality from other respiratory viruses were distributed evenly between the three defined seasons.

CONCLUSION

Influenza and RSV substantially increased hospitalization rates, antibiotic use, and deaths in elderly nursing home residents each winter. These data should encourage persistent efforts toward disease prevention, and thoughtful study of vaccine development and delivery, diagnostic tools, and methods of prophylaxis and therapy.

Incidence of amantadine-resistant influenza A viruses in sentinel surveillance sites and nursing homes in Niigata, Japan

We surveyed the incidence of amantadine-resistant influenza A viruses both at sentinel surveillance sites and at nursing homes, and verified their types of change by partial nucleotide sequence analysis of the M2 protein. Fifty-five influenza A viruses from 27 sentinel surveillance sites during six influenza seasons from 1993 to 1999, and 26 influenza A viruses from 5 nursing homes from 1996 to 1999 were examined for susceptibility to the drug by virus titration in the presence or absence of amantadine. While amantadine-resistant viruses were not found in sentinel surveillance sites, a high frequency of resistance (8/26, 30.8%) in nursing homes was observed. Resistant viruses can occur quickly and be transmitted when used in an outbreak situation at nursing homes, where amantadine is used either for neurologic indications or for influenza treatment. Eight resistant viruses had a single amino acid change of the M2 protein at residue 30 or 31. In vitro, all 11 sensitive viruses turned resistant after 3 or 5 passages in the presence of 2 microg/ml amantadine, and they showed an amino acid change at residue 27, 30, or 31. The predominant amino acid substitution in the M2 protein of resistant viruses is Ser-31-Asp (a change at 31, serine to asparagine). The results indicate that a monitoring system for amantadine-resistant influenza viruses should be established without delay in Japan.

Influenza vaccine, anti-influenza drugs, and rapid diagnosis in Japan

The percentage of individuals receiving influenza vaccine is markedly lower in Japan than in many other economically advanced countries. To increase the rate of coverage, the current practice of giving people two inoculations instead of one needs to be changed. In addition, free vaccination services for the elderly and high-risk patients need to be offered. Amantadine is available for the treatment of influenza type A infection in Japan. Moreover, zanamivir, a neuraminidase inhibitor effective against both influenza type A and B viruses, has been approved in Japan. A rapid diagnosis kit for influenza type A virus is available in Japan. With the current threat of new pandemic influenza viruses emerging, it is necessary to actively confront influenza in Japan by increasing the vaccine coverage rate, by employing amantadine and neuraminidase inhibitors for influenza virus infection, and by providing rapid diagnosis of influenza.