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Influenza in Older Patients: A Call to Action and Recent Updates for Vaccinations
Miranda Wilhelm, PharmD
Participating Faculty

Influenza in Older Patients: A Call to Action and Recent Updates for Vaccinations

Miranda Wilhelm, PharmD
Pneumonia may be caused by the influenza virus, another virus (eg, respiratory syncytial virus), or bacteria (eg, Streptococcus, Staphylococcus). Primary influenza viral pneumonia can develop rapidly, within 2 to 5 days of the onset of symptoms, and may require intubation and mechanical ventilation.9 Influenza and bacterial coinfection occur in 11% to 35% of patients.11 The most commonly encountered bacteria are Streptococcus pneumoniae and Staphylococcus aureus, accounting for 35% and 28% of identified coinfecting bacteria, respectively. Other pathogens encountered include Pseudomonas aeruginosa, Streptococcus pyogenes, Haemophilus influenzae, Klebsiella pneumoniae, and Mycoplasma pneumoniae. Secondary bacterial pneumonia should be suspected in patients who initially improve, but then worsen within 2 weeks of the onset of influenza symptoms.9

Less Common Complications

Less common serious complications of influenza infection occur in extrapulmonary sites.12 Most often, extrapulmonary complications are associated with the acute phase of the infection. Weeks later, other symptoms, particularly those that affect the central nervous system (eg, Guillain-Barré syndrome, encephalitis, Reye syndrome), and exacerbations of pre-existing comorbidities (eg, myocarditis/pericarditis) may follow. The possibility of late-onset sequelae remains controversial.

Myocarditis has been reported in approximately 0.4% to 13% of hospitalized adult patients with documented influenza, based on elevation of cardiac enzymes and echocardiographic findings.13 In fatal influenza infections, myocarditis and myocyte necrosis have been observed in approximately 30% to 50% of patients at autopsy.12 However, it appears to be more common among younger patients, with 68% of cases in patients younger than 40 years.

Neurologic complications are rare and affect mainly children, although they can affect adults.12 People of Asian/Pacific Islander descent appear to be more susceptible than white, non-Hispanic patients (occurrence rate per million persons of 12.79 vs 3.09, respectively).14

Other complications of influenza infection have been noted, including rhabdomyolysis, ocular manifestations (eg, conjunctivitis, retinopathy, uveal effusion syndrome, optic neuritis), acute kidney injury, hepatic injury, hematologic complications, and complications related to diabetes.12 However, the mechanisms linking these complications with influenza infection are not clear.

The Burden of Illness of Influenza in Older Populations

It is important that older patients receive annual influenza vaccination.9,15 Vaccines are a proven method of reducing the spread of influenza.1 The CDC recommends that all persons older than 6 months receive the vaccine. Importantly, healthcare workers should receive the vaccine to reduce the spread of the virus, particularly if they care for at-risk patients (eg, long-term care residents).1

Rate of Vaccination

Seasonal influenza is associated with significant morbidity and mortality. From 2010-2011 to 2015-2016, influenza-related hospitalizations in the United States ranged from a low of 140,000 (during 2011-2012) to a high of 710,000 (during 2014-2015).1 The hospitalization rate in the 2016-2017 season was 65.0/100,000 for all age groups, and 290.5/100,000 for adults 65 years or older.16

Mortality data are not typically available for 3 years after an influenza season because of the need to model the data. Relying on death certificates for enumerating mortality has several problems, including incomplete and inaccurate reporting. Data modeling circumvents these deficits. The CDC estimates that, between 2010 and 2014, there were 12,000 to 56,000 deaths from seasonal influenza.1

Vaccine Coverage

The global target vaccination coverage rate for persons 65 years or older is 75%; in the United States, it is 90%.17 This target is rarely met in the industrialized world, and the developing world has even poorer coverage.17 The influenza vaccination coverage rate in the United States for the 2016-2017 season was 65.3% in adults 65 years or older, representing an increase of 1.9% over the previous year (Figure 3).1 However, 2015-2016 saw the lowest coverage rate since 2010. The average coverage over the past 7 seasons (2010-2011 to present) has remained at 65.4% (range, 63.4%-66.7%).1

Significant barriers to full coverage exist.18 Lack of confidence in the vaccine and personal complacency are major reasons people skip vaccination. Vaccine avoidance is higher among people with negative attitudes toward vaccines and health authorities and those who perceive vaccines as ineffective. Some people are worried about the safety of vaccines (eg, mercury in thimerosal), perceive the threat of illness as low (eg, generally healthy people), or do not receive encouragement from healthcare providers to be vaccinated. On the other side, people with positive attitudes toward influenza vaccines, high perceived utility of vaccination, cues to action (eg, peers and healthcare providers), and previous influenza vaccinations are more likely to be vaccinated.

Strategies proven to increase adult vaccination rates include screening all patients for immunization status at each visit, educating patients about the importance of vaccination, and providing a strong recommendation to receive needed vaccines. In addition, systems can facilitate vaccination rates by reminding providers about needed vaccines and using alerts to schedule follow-up doses for multidose series.

Vaccine Effectiveness

Because of genetic drift and constant antigenic changes on the virus, people should receive the influenza vaccine each year for optimal protection.1 Vaccine production requires about 9 months to build adequate reserves. The CDC makes a best educated guess at which strains will be prominent in the next influenza season. Often, this guess is a good match between viruses in the vaccine and that season’s circulating viruses. However, sometimes, the vaccine and circulating viruses are mismatched to a degree. This results in reduced vaccine effectiveness. Over the past decade, the overall vaccine effectiveness has hovered in the 40% to 55% range, although some years have been better or worse than others (Figure 4).1 For instance, the 2014-2015 season was particularly bad, with vaccine effectiveness of less than 20%. The influenza vaccine is composed of 3 or 4 viral components. Even if the vaccine is not matched directly to the circulating viruses of that season, it can provide benefits, including reduced severity, due to cross-protection, and protection against viruses that were successfully matched in the vaccine. In an analysis of the 2013-2014 influenza season (the most recent for which data are available), vaccination reduced the odds of in-hospital deaths (adjusted odds ratio [aOR], 0.39; 95% CI, 0.17-0.66), ICU admission (aOR, 0.63; 95% CI, 0.48-0.81), length of ICU stay (adjusted relative hazard [aRH], 1.34; 95% CI, 1.06-1.73), and hospital length of stay (aRH, 1.24; 95% CI, 1.13-1.37) in patients 65 years or older.19 Becoming infected with influenza does not prevent a person from becoming infected the next year, or even in the same season; again, this is due to genetic drift or infection with an unrelated influenza virus. The influenza vaccine does not protect people against other respiratory viruses and illnesses.

Vaccine Timing

Ideally, individuals should be vaccinated several weeks before the influenza season because immunity does not build to sufficient levels until 2 weeks after vaccination. The CDC recommends that people be vaccinated before influenza virus is circulating in the community, and by the end of October at the latest. Getting vaccinated later in the season can be beneficial, but it delays protection and could result in influenza infection.1

A recent examination of vaccine effectiveness among enrollees (all ages) in the US Influenza Vaccine Effectiveness Network for the 2011-2012 through 2014-2015 influenza seasons supports the notion that effectiveness wanes with time.20
  • Adjusted vaccine effectiveness against influenza A (H3N2) virus infection decreased from a maximum of 35% at 14 days post vaccination and reached zero at 158 days (7% decline per 30-day period)
  • Adjusted vaccine effectiveness against influenza A (H1N1)pdm09 virus infection decreased from a maximum of 80% at 14 days post vaccination and reached a minimum of 37% at 128 days (6%-11% decline per 30-day period)
  • Adjusted vaccine effectiveness against influenza B virus infection decreased from a maximum of 59% at 14 days post vaccination and reached a minimum of 23% at 180 days (7% decline per 30-day period)

There is concern that immunity in elderly persons declines more rapidly than in younger people, and that it may not last through the entire season.21-23 However, this may reflect a poorer primary response to vaccination.21 Skowronski et al reviewed 8 studies, results of which reported seroprotection rates in persons 65 years or older.22 They found that adequate seroprotection rates were maintained 4 months or longer, by Committee for Proprietary Medicinal Products standards, in all 8 of the studies reporting for the H3N2 component and in 5 of the 7 studies reporting for the H1N1 and B components. Their review suggested that the primary response to vaccination was of greater predictive importance than secondary antibody decline post vaccination. For those people who seroconverted for the H3N2 and H1N1 vaccine components, seroprotection rates of 70% to 100% were observed in 2 studies at 4 months, 2 studies at 5 months, and 4 studies at longer than 6 months. Less consistent seroprotection against the B component was observed. Seroconversion was inversely correlated with preimmunization titers but not with age.22

Toolkits for Expanding Coverage

The CDC has many toolkits to assist healthcare personnel and institutions improve vaccination coverage.1 These include:
  • General campaign materials for employers, healthcare personnel, and the public
  • Toolkits for establishing and improving an influenza vaccination program
  • Cultural and language resources
  • Guidance for promoting influenza vaccination in a facility
These materials are available as Web-based materials, printable materials, and/or videos/podcasts.24 The toolkits include influenza fact sheets for employers, healthcare personnel, and patients; best practice guidance documents and checklists for patient safety and vaccine effectiveness; and forms and educational content in a variety of languages.

Influenza Vaccination Products for Use in Older Adults

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