Flu seasons are unpredictable and can be severe. Flu-associated deaths in the US range from 3,000 to about 49,000 each year depending on the severity and communicability of the circulating viruses. Mortality is most common in elderly persons, but deaths occur in all age groups, including children. Hospitalizations due to complications from influenza are highest at the extremes of age, with infants and toddlers hospitalized at rates comparable to older persons.
Vaccination is the primary means of prevention
Influenza vaccination is the most effective means of prevention and is recommended annually for all persons 6 months of age and older. Influenza vaccine is available in four forms:
- Traditional injected vaccine is approved for everyone age six months and older
- Nasal spray vaccine is approved for healthy people age two through 49 years
- Intradermal vaccine (smaller needle) is approved for adults age 18 through 64 years
- High-dose vaccine is approved for people age 65 years and older
The range of choices means there is a vaccine option that’s right for everyone age six months and older in this country. Because older persons tend to have a diminished immune response to vaccination, the high-dose vaccine includes four times the amount of antigen as traditional vaccines to help people age 65 years and older mount a protective response. Intradermal vaccine is injected into the skin rather than the muscle and provides an option for adults who want a smaller needle. Traditional injected and nasal spray vaccines have been used safely and effectively for many years.
Influenza onset is abrupt and complications can be severe
Following a one- to four-day incubation period (during which asymptomatic persons may transmit the virus), influenza is usually marked by abrupt onset of fever (up to 104ºF), myalgia, sore throat, and a non-productive cough. Additional symptoms may include rhinorrhea, headache, chills, photophobia, and malaise. Children may also exhibit symptoms uncommon in adults (eg, diarrhea, vomiting, and nausea).
The most common complication of influenza is secondary bacterial pneumonia. Influenza is also associated with other serious illnesses, including encephalopathy, Reyes syndrome, myocarditis, and pericarditis.
Influenza viruses mutate; annual vaccination is necessary
There are three influenza antigen types--A, B, and C. Influenza A usually causes moderate to severe illness and affects all age groups. Influenza B usually causes mild disease and primarily affects children. Influenza C is rarely reported in humans. The influenza vaccine is a trivalent combination including one influenza B and two influenza A strains. It is reformulated annually, with strains chosen by the FDA in collaboration with the World Health Organization to match the strains anticipated to circulate during the following season. Annual vaccination is necessary for optimal protection.
While the vaccine is a good match to circulating strains in the majority of years, influenza viruses can undergo minor changes or mutations, leading to new strains. Scientists call this change "antigenic drift." Drift is an ongoing process and is one way the virus evades the body's immune system.
Larger and more abrupt changes in influenza viruses, called ”antigenic shift” can lead to worldwide pandemic if the new virus is easily transmitted between humans, because most people would have minimal to no immunity against the new strain. Antigenic shift led to three pandemics during the last century (1918-20, 1957-58, 1968-69).
Influenza vaccines are safe
All influenza vaccines are safe and well tolerated. The most common adverse events associated with injected vaccines are mild and transient local reactions (eg, soreness, induration, erythema). The most common adverse events associated with the nasal spray are runny nose and headache across all ages. Children may also experience wheezing, vomiting, muscle aches, and fever, while adults may experience sore throat and cough.
People with a mild allergy to eggs or egg protein, such as those who experience hives, can receive the inactivated influenza vaccine. People with egg allergies should be observed for at least 30 minutes following vaccination. Neither inactivated nor live influenza vaccines should be administered to anyone with a history of a severe reaction to the vaccine or severe systemic (eg, anaphylactic) reaction to eggs or egg proteins.
Everyone age six months and older should be vaccinated annually
Everyone age six months of age and older should be vaccinated annually to protect against influenza. For everyone over age nine, this requires one vaccination each year. Children younger than nine may require more than one dose of vaccine to be fully protected.
While certain groups are at increased risk of serious outcomes from influenza (eg, elderly, infants, toddlers, people with certain chronic conditions), anyone, even the healthiest young adult, can have a serious outcome or die from influenza.
Influenza Immunization Among Healthcare Professionals - Call to Action
NFID has a long commitment to increasing annual influenza vaccination rates among healthcare professionals. NFID issued a Call to Action in 2008 to help draw attention to the issue and serve as a key resource in educating healthcare professionals (HCPs) about the effects of influenza in healthcare settings. Following publication of the Call to Action, the issue was elevated on the national level, with CDC and accrediting and professional organizations, such as The Joint Commission, supporting efforts to increase HCP influenza vaccination rates as an important component of patient safety. There have also been numerous successful initiatives at the local level.
The result is that influenza vaccination rates among HCPs have increased slowly over the past decade, reaching 63.5 percent during the 2010-2011 influenza season. However, coverage is still well below the Healthy People 2020 target of 90 percent. Coverage was highest among physicians, HCPs working in hospital settings, and older HCPs. Near universal coverage (98.1 percent) was achieved among HCPs who reported being subject to an employment requirement for vaccination.