Influenza vaccination of residents of long-term care facilities (and of health care workers at these facilities) is critical for the prevention of influenza in this frail population. Detection, chemoprophylaxis, and treatment have limitations. Infection control measures should be in place during and between outbreaks. Acute care facilities such as emergency departments and hospitals can assist by testing residents of long-term care facilities who present with influenza-like illness during seasonal epidemics of influenza, and by notifying the receiving facility if a patient with influenza would be arriving.
THE EXTENT OF THE PROBLEM
From 5% to 20% of the US population, including residents and health care workers in long-term care facilities, are infected with influenza every year.1,2 The proportion of those infected who develop clinical illness ranges from 40% to 80%. Each influenza illness is associated with an average of 10 days of respiratory sickness, resulting in approximately 3 days of bed confinement or restricted activity. About 30% to 50% of patients with microbiologically confirmed influenza seek medical care, of whom 16% undergo laboratory tests, 17% undergo radiologic tests, and 75% are recommended an over-the-counter drug or are prescribed a medication. Annual influenza-related hospitalizations range from 200,000 to 400,000, depending on seasonal variations in virulence.2,3 Thus, influenza causes 1.3 hospitalizations per 1,000 people, and 25% of these are in people age 65 and older. In the United States, about 40,000 to 60,000 people die of influenza every year, and 90% of these are age 65 and older.4
POLICIES TO FIGHT ANTIVIRAL RESISTANCE
In January 2006, the US Centers for Disease Control and Prevention (CDC) recommended against the use of the adamantanes—ie, amantadine (Symmetrel) and rimantadine (Flumadine)—for the treatment or prevention of influenza because of a high level of resistance in circulating influenza A/H3N2 in the community. Unfortunately, this resistance trend has not reversed since then, with 96% to 100% of influenza A/H3N2 isolates in the United States showing resistance.5 During the 2007–2008 influenza season, influenza A/H1N1 isolates resistant to oseltamivir (Tamiflu) emerged in Europe, particularly in Norway and France. In the United States, influenza A/H1N1 resistance to oseltamivir increased from 0.7% in the 2006–2007 season, to 10.9% in the 2007–2008 season, and to 98% during the 2008–2009 season.6,7
Fortunately, all oseltamivir-resistant isolates remain susceptible to zanamivir (Relenza). In April 2009, a new influenza A/H1N1 variant (previously referred to as swine-origin influenza virus, or SOIV) emerged in North America and spread to many countries worldwide, and the World Health Organization eventually declared a pandemic. This new variant is susceptible to oseltamivir and zanamivir but resistant to the adamantanes. Resistance patterns for future influenza seasons cannot be predicted, but the current extent of influenza resistance and its development over the past decade8 are alarming.
WHY IS INFLUENZA MORE SERIOUS IN LONG-TERM CARE RESIDENTS?
Influenza is usually introduced to long-term care facilities by workers and visitors. Inside, the closed environment and limited mobility of residents facilitate transmission of infection.
The clinical presentation of influenza in residents of long-term care facilities can be subtle, with a blunted febrile response and a decline in mental and functional status.9
Residents commonly have underlying diseases that can be exacerbated by influenza infection, such as congestive heart failure, chronic obstructive lung disease, chronic kidney disease, and dementia. In addition, residents are at higher risk of serious influenza-related complications than are community-dwelling elderly people.
Impaired oral intake, limited dexterity, and altered consciousness may limit treatment options, thus further adversely affecting outcomes. Bacterial pneumonia secondary to influenza has dire consequences in long-term care residents. Rates of hospitalization for pneumonia and influenza and for exacerbation of chronic lung disease are higher in these patients than in their community-dwelling counterparts.10 Death rates are also higher, exceeding 5% during influenza epidemics.11
PREVENTING INFLUENZA IN LONG-TERM CARE FACILITIES
Immunizing residents is essential
Vaccination is the most important measure in preventing influenza in long-term care facilities, and vaccination programs should include residents and health care workers.
Influenza outbreaks are more common in facilities where the rate of immunization is below 80%, as well as in larger facilities (with > 100 beds), suggesting that herd immunity may play a role.12 Unfortunately, influenza vaccine coverage rates vary widely in this patient population—from 57% to 98% in one report.13
The live-attenuated intranasal vaccine is approved only for healthy people under age 50, so most residents of long-term care facilities should receive only the inactivated trivalent intramuscular vaccine.
The effectiveness of a vaccine in preventing influenza depends in part on the adequacy of the match between vaccine serotypes and circulating strains. Studies of all types—randomized, observational, case-control, and cohort studies, as well as meta-analyses and systematic reviews—have shown preventive efficacy rates of influenza vaccination in elderly residents of long-term care facilities to be 23% to 43% for influenza-like illness, 0% to 58% for influenza, 46% for pneumonia, 45% for hospitalization, 42% for death from influenza or pneumonia, and 60% for death from all causes.14,15 Vaccine performance improved after adjustment for confounders.
Obviously, this protection is variable and incomplete, since influenza outbreaks continue to occur even in long-term care facilities in which most residents are vaccinated.13