Influenza season is from November through April in the US. Each year, the influenza virus changes after an outbreak. A new influenza vaccine must be manufactured each year, in order to be effective against the new virus. Influenza vaccinations are given at the beginning of each flu season. Although the vaccine does not guarantee protection from infection, the risk of infection is reduced greatly.
There are three types of influenza vaccine:
- Influenza immunization by injection:
- Influenza immunization by nasal spray:
- Influenza virus vaccine, intranasal (FluMist)
- Influenza vaccine by injection (now includes H1N1)
On July 29, 2010, the CDC's Advisory Committee on Immunization Practices (ACIP) issued recommendations for everyone 6 months of age and older who do not have any contraindications to vaccination, to receive a flu vaccine each year, beginning this (2010 - 2011) flu season.
ACIP recommends that children 6 months through 8 years of age receive 2 doses of the 2010-2011 flu vaccine with a minimal interval of 4 weeks unless they have received:
- At least 1 dose of 2009 H1N1 flu vaccine last season; and
- At least 1 dose of seasonal flu vaccine prior to the 2009-2010 flu season or 2 doses of 2009-2010 seasonal flu vaccine.
Annual influenza vaccine is strongly recommended for the following:
- Children from 6 months to 18 years of age
- Caregivers of children under the age of 6
- Anyone over 50 years old
- Caregivers of people over 50
- Those who live in crowded conditions:
- Correctional facilities
- Those who take daily oral corticosteroid medication:
- Health care workers
- Nursing home residents
- Pregnant women
- Those who have:
This vaccine should not be given to the following persons:
- Anyone who has had Guillain-Barre syndrome
- Anyone who is ill with a fever over 100.4 degrees F (38 C)
- Anyone with an allergy to eggs
- Females in the early stages of pregnancy
Side effects from influenza vaccination in adults are relatively rare. In children, side effects may be more common. Influenza vaccine cannot cause influenza. The most commonly reported effect is soreness around the vaccination site for several days after the vaccination. This can occur in about one out of every three people getting this vaccine.
Other reported side effects include:
Side effects are most common in those who have not been exposed to the influenza vaccines, such as young children. These reactions begin 6 to 12 hours after vaccination and can last for 1 or 2 days. Minor symptoms can be treated with acetaminophen or ibuprofen. Avoid the use of aspirin in children because of the risk of Reye's syndrome.
Immediate allergic responses to flu vaccine occur very rarely. When they do occur it is usually within minutes to hours of receiving the shot. Severe allergic reactions may cause hives, breathing problems, horse voice, paleness, dizziness, and low blood pressure. There have been rare reports of Guillain-Barre syndrome (GBS) after a flu vaccine.
Despite a small chance of a serious reaction, there is no doubt that the vaccination is safer than the risks of influenza. Vaccination is also far less expensive and more effective than using anti-flu medicines for a flu infection or exposure.
Home care of minor influenza vaccine reactions:
- Use acetaminophen or ibuprofen for mild fever, aches and pains.
- Use warm compresses to help relieve inflammation.
- Mild redness and swelling of the injection site may be expected.
Notify your doctor if:
- You become very weak, confused or disoriented after the vaccine
- You develop a high fever or persistent vomiting after the vaccine
- You develop a new seizure or fit after the vaccine
- You develop a widespread rash after the vaccine
- You develop increasing pain, redness and swelling of the injection site that does not respond to home care
- You develop a boil or draining pus from the injection site
- You develop worsening weakness in the legs after the vaccine
Continue to Influenza Outlook
- Centers for Disease Control and Prevention (CDC)
- Ebell MH, White LL, Casault T. A systematic review of the history and physical examination to diagnose influenza. J Am Board Fam Pract. 2004 Jan-Feb;17(1):1-5. 
- Flu.gov, HHS Interagency Public Affairs Group on Influenza Preparedness and Response
- Jefferson T, Smith S, Demicheli V, Harnden A, Rivetti A, Di Pietrantonj C. Assessment of the efficacy and effectiveness of influenza vaccines in healthy children: systematic review. Lancet. 2005 Feb 26-Mar 4;365(9461):773-80. 
- Montalto NJ. An office-based approach to influenza: clinical diagnosis and laboratory testing. Am Fam Physician. 2003 Jan 1;67(1):111-8. 
- Strategy for Off-Site Rapid Triage(c) (SORT) and Real-time Epidemiological Assessment for Community Health(c) (REACH), Emory University, Principal Investigators: Alexander Isakov, MD, MPH; Arthur Kellermann, MD, MPH, Collaboration with the Emory at Grady Health Literacy Team (Ruth Parker, MD; Kara Jacobson, MPH, CHES; Lorenzo DiFrancesco, MD)
- VHA Office of Public Health Surveillance and Research; Influenza Algorithm Work Group