Influenza: Why should I get the vaccine?

What is influenza?

Influenza is an acute respiratory illness caused by Influenza A and Influenza B virus. It mainly is prevalent during the winter season. Although the virus can be debilitating, it is a self-limited infection in the general population. This is termed uncomplicated influenza. The worst cases that cause an increase in morbidity and mortality in certain-high risk populations are cases of complicated influenza.

What is the current status of the virus?

The CDC gathers information and updates their website weekly. At the end of January 31, 2015 the CDC reports there have been 21 cases of H1N1 and 569 cases of H3N2. In the United States, the majority of recently circulating influenza virus have been susceptible to oseltamivir (Tamiflu), zanamivir, and peramivir. It should be noted that there have been some strains that are resistant to Tamiflu; this includes the H1N1 and H3N2 detected worldwide.

The CDC still recommends antiviral treatment with oseltamivir, zanamivir, or peramivir as early as possible for patients who are confirmed or suspected influenza who have severe, complicated, or progressive illness. You can find more information by visiting the CDC.

How is influenza transmitted?

Transmission of the virus often is as a result of contact with an infected person. This can be from respiratory secretions, like sneezing and coughing. Large particle droplets do not remain suspended in the air and they travel only short distances (about 6 feet).

In healthy adults, viral shedding can be detected 24 to 48 hours before illness onset. In clinical trials, shedding ceased after 6 to 7 days in most studies, up to 10 days in some trials.

In the elderly, immune suppressed, and those with chronic illnesses, viral shedding was detected on average 6 days.

What makes influenza so "complicated" if it is self-limited?

Pneumonia is the most common complication of influenza. This can range from primary influenza pneumonia, which can be severe enough that causes hypoxia and even death. In addition, secondary bacterial pneumonia contributes substantially to morbidity and mortality. This is especially concerning in the population aged greater than 65 years of age.

Cardiac complications include heart attack, inflammation around the heart, including myocarditis and pericarditis.

What is the treatment?

Given the growing resistance to antiviral agents, physicians have the responsibility of reserving these agents for those who are at high risk for complications, hospitalizations, and evidence of lower respiratory tract infection.

The current recommendation is to treat with zanamivir and oseltamivir for all individuals confirmed or suspected of influenza virus infection who are severely ill. Antiviral treatment should be within 48 hours of symptom onset. There is also evidence to use antiviral agents for outpatient patients who present more than 48 hours after symptom onset with confirmed or suspected influenza infection and who are at increased risk for complications provided they are still not improving.

If an individual has uncomplicated influenza then antiviral agents are generally not recommended. The usual over the counter medications to help with symptoms, plenty of rest, fluids, and nutrition should suffice to treat this illness.

What is the value in getting the flu vaccine?

Remember from the above discussion that there are 2 types of influenza: A and B. The current vaccine protects individuals from type A H1N1 and other subtypes of type A influenza as well as type B. The prevalent H3N2 strain is resistant to the current vaccine. This should NOT prevent individuals from getting vaccinated.

During the 2003-2004 influenza season, according to the CDC, the inactivated influenza vaccine effectiveness against the laboratory-confirmed influenza was 60% among healthy persons and 48% among those with high-risk medical conditions in a case-control study among people 50-64 years old.

The live vaccine has been shown to be associated with reductions in severe febrile illnesses of 19% and febrile upper respiratory tract illnesses of 24% in healthy adults according to the CDC.

Please visit http://www.cdc.gov/flu/professionals/vaccination/effectivenessqa.htm for more information.

The data also suggests that as a society, the flu vaccine reduces health care costs. Thus, there is not only a health benefit, but also an economic benefit of getting vaccinated. I encourage you to inform yourself of the illness and the vaccine to make more informed decisions for you and your loved ones. As always, consult with your primary care physician if you have any other questions.