Temporal surveillance of the humoral immunity against influenza vaccine in the elderly over 9 consecutive years

Older Human B Cells and Antibodies

B cells have a number of different roles in the immune response. Their excellent antigen presentation potential can contribute to the activation of other cells of the immune system, and evidence is emerging that specialized subsets of these cells, that may be increased with age, can influence the cell-mediated immune system in antitumor responses. They can also regulate immune responses, to avoid autoreactivity and excessive inflammation. Deficiencies in regulatory B cells may be beneficial in cancer but will only exacerbate the inflammatory environment that is a hallmark of aging. The B cell role as antibody producers is particularly important, since antibodies perform numerous different functions in different environments. Although studying tissue responses in humans is not as easy as in mice, we do know that certain classes of antibodies are more suited to protecting the mucosal tissues (IgA) or responding to T-independent bacterial polysaccharide antigens (IgG₂) so we can make some inference with respect to tissue-specific immunity from a study of peripheral blood. We can also make inferences about changes in B cell development with age by looking at the repertoire of different B cell populations to see how age affects the selection events that would normally occur to avoid autoreactivity, or increase specificity, to antigen.

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.

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.

Lack of correlation between nutritional status and seroprotection against influenza in a long term care facility

We conducted a prospective study in a long-term care facility. Virologic diagnosis was assessed using viral isolation, polymerase chain reaction and serology for all patients with a flu-like syndrome. Albumin, vitamins and trace elements were also measured.

RESULTS

The risk of influenza increased 6.5-fold in patients with an antibody titer of 40 during the influenza outbreak (P=0.04). Micronutrients and vitamins deficiencies were important. Patients with antibody titer >1:40 could still be infected by the virus without correlation with the nutritional status.

CONCLUSION

Humoral protection with a titer >1:40 might not be protective in the elderly. Nutritional deficiencies were too prevalent to detect any effect on the results.

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.

Immunity and immunization in elderly

As the average life expectancy increases, retired people want to travel. Five to 8% of travellers in tropical areas are old persons. Immune system suffers of old age as the other organs. The number and the functions of the T-lymphocytes decrease, but the B-lymphocytes are not altered. So, the response to the vaccinations is slower and lower in the elderly. Influenza is a great cause of death rate in old people. The seroconversion, after vaccine, is 50% from 60 to 70 years old, 31% from 70 to 80 years old, and only 11% after 80 years old. But in public health, the vaccination reduced the morbidity by 25%, admission to hospital by 20%, pneumonia by 50%, and mortality by 70%. Antipoliomyelitis vaccine is useful for travellers, as the vaccines against hepatitis and typhoid fever. Pneumococcal vaccine is effective in 60%. Tetanus is fatal in at last 32% of the people above 80 years, therefore this vaccine is very important.