Facts about Influenza for Adults

What is Influenza 
Influenza (the “flu”) is a contagious viral infection primarily of the nose, throat, and lungs. Flu is caused only by the influenza virus, but many people confuse illnesses caused by other viruses or bacteria, including severe colds (rhinovirus) or “the stomach flu” (norovirus and other viruses and bacteria) with influenza.

Influenza occurs mainly in the fall and winter months in the US and infects anywhere from 5-20 percent of the population each year. Flu seasons are unpredictable and can be severe. For example, between 1976 and 2006, estimates of flu-associated deaths in the US ranged from a low of about 3,000 to a high of about 49,000 people. Unfortunately, there is no way to know beforehand whether any one flu season will be mild or severe.

Influenza symptoms can include fever, aches, chills, tiredness, and sudden onset. Other symptoms may include cough, runny/stuffy nose, and /or sore throat. Unlike other common respiratory infections that are often called “the flu,” influenza can cause more severe illness that can result in complications leading to hospitalization and death. However, whether symptoms are mild or severe, people can still spread influenza virus to others. In fact, they can spread influenza even before the show any symptoms.

An annual flu vaccine is the best way to prevent influenza. The time to vaccinate is as soon as vaccine becomes available, which can even be by late summer, and any time throughout the influenza season. Vaccination is needed annually for the best protection, as the vaccine is usually updated from one season to the next to protect against the influenza viruses that are most likely to circulate and immunity to influenza declines over time.

Who should get influenza vaccine? 
Annual influenza vaccination is recommended for everyone age 6 months and older. For adults, that means a vaccine each year. Pregnant women are specifically encouraged to get vaccinated and may receive the vaccine any time during their pregnancy. The vaccine is available in several forms:

  • The traditional injected vaccine includes inactivated (or killed) virus and is approved for everyone six months and older.
  • Nasal spray vaccine includes live, but weakened virus and is approved for healthy people age two through 49 years.
  • Intradermal vaccine that is injected into the skin rather than the muscle because it uses a smaller needle; includes inactivated (or killed) virus, and is approved for adults age 18 through 64 years, and may appeal to those who do not like needles.
  • High-dose vaccine containing four times the amount of antigen to induce a greater immune response in people 65 and older.
It is worth noting that children six months through eight years being vaccinated for the first time need two vaccine doses separated by four weeks.Also, infants younger than six months cannot get influenza vaccine, but they are at high risk of serious complications and hospitalization if they get influenza. The best way to protect them is to be sure everyone around them is vaccinated and for pregnant women to be vaccinated. Infants born to vaccinated women are protected against flu for the first six months of their lives.

UPDATE: On June 22, 2016, the CDC Advisory Committee on Immunization Practices (ACIP) recommended a change to US influenza vaccination policy for 2016-2017. ACIP voted that live attenuated influenza vaccine (LAIV), also known as the “nasal spray” flu vaccine, should not be used during the 2016-2017 flu season. ACIP continues to recommend annual flu vaccination, with either the inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV), for all individuals age 6 months and older.  

Vaccine safety 

All types of influenza vaccines are safe and well tolerated. The injected vaccines may result in some mild soreness, redness, or swelling at the injection site lasting one to two days. Other possible mild side effects include a headache and low-grade fever for a day after vaccination. The nasal spray vaccine may result in a runny nose, headache, low-grade fever, sore throat, fatigue or cough after vaccination. The potential risks associated with influenza are much greater than the potential risks associated with vaccination.
Disease and vaccine facts
  • FACT: Influenza vaccines are safe and are the best way to help prevent influenza.
  • FACT: Every adult in the US should get the influenza vaccine every year.
  • FACT: Circulating influenza viruses change often, which affects how severe and how common the illness is from year to year.
  • FACT: Flu seasons are unpredictable and can be severe. Between 1976 and 2006, estimates of flu-associated deaths in the US ranged from a low of about 3,000 to a high of about 49,000 people. 
  • FACT: In the US, more than 200,000 individuals are hospitalized by influenza every year, including 20,000 children.
  • FACT: Infants younger than six months cannot get influenza vaccine, but they are high risk of serious complications and hospitalization if they get the flu. The best way to protect them is by vaccinating everyone around them.
  • FACT: The flu is caused only by influenza virus. People often mistake other, less severe illnesses with influenza, like the common cold or the “stomach flu,” which is not influenza at all. Stomach illnesses are caused by other viruses, like norovirus, and many types of bacteria.
  • FACT: Total direct hospitalization costs of a severe influenza epidemic are estimated to be over $6 billion.
  • FACT: Influenza vaccine is needed every year because the immunity wears off over time and also because in most years the vaccine is updated to match circulating strains.
  • FACT: Influenza can make chronic conditions worse. It can be associated with heart attacks, make it harder for diabetics to control their sugar levels, make asthma worse, and lead to pneumonia.

1. Special note for 2011-2012 season: children ages six months through eight years who received at least one dose of 2010-2011 influenza vaccine require just one dose of 2011-2012 vaccine.

January 2012

For more information, speak with your healthcare professional or visit www.adultvaccination.org.