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Influenza Vaccination: A Summary for Clinicians

Influenza vaccination is the most effective method for preventing influenza virus infection and its potentially severe complications.

  • There are two types of influenza vaccine: Trivalent Inactivated Influenza Vaccine (TIV) (pdf) and Live, Intranasal Influenza Vaccine (LAIV) (pdf).
  • TIV is injected into the muscle of the upper arm or thigh. It can be used for people 6 months of age or older, including healthy people, those with chronic medical conditions, and pregnant women.
  • LAIV is given as a nasal spray. It can be used for healthy* people 2-49 years of age who are not pregnant.
  • Influenza vaccine reduces the likelihood of becoming ill with influenza or transmitting influenza to others.                                            

When should vaccination occur?
Providers should begin vaccinating their patients as soon as they have influenza vaccine and should continue to offer vaccine to their patients in December and later. While influenza outbreaks can happen as early as October, most of the time influenza activity peaks in January or later.  

When should health care providers start and stop vaccination efforts?

Beginning each September, or even earlier if vaccine is available, the flu vaccine should be offered to people when they are seen by health care providers for routine care or as a result of hospitalization.
 
However, persons and institutions planning substantial organized vaccination campaigns (e.g., health departments, occupational health clinics, and community vaccinators) should consider scheduling these events after at least mid-October, because the availability of vaccine in any location cannot be ensured consistently in early fall. Scheduling campaigns after mid-October will minimize the need for cancellations because vaccine is unavailable. These vaccination clinics should be scheduled through December, and later if feasible, with attention to settings that serve children, pregnant women, other persons younger than 50 years of age at increased risk for influenza-related complications, persons aged 50 years and older, health care personnel, and persons who are household contacts of children aged younger than 60 months (5 years) or other persons at high risk.

In addition, vaccination efforts should be structured to ensure the vaccination of as many persons as possible over the course of several months, with emphasis on vaccinating before influenza activity in the community begins. Even if vaccine distribution begins before October, distribution probably will not be completed until December or January. Flu seasons vary in terms of length and severity. As a result, instead of setting a firm date to stop vaccinating, CDC generally recommends that vaccination efforts continue as long as influenza is circulating in the community. Clinicians should be aware that more than one wave of influenza can occur in communities, and that a decline in influenza illnesses during the fall or winter might be followed by another increase in illness caused by a different influenza virus strain. Clinicians deciding whether to continue vaccination efforts into May may consider accessing state and/or local influenza surveillance information to determine if flu is still circulating in the community.
However, end-of-season vaccination (in April and May) may particularly benefit the following people:

  • Persons likely to be traveling to the Southern Hemisphere, where influenza may be circulating before the 2009-10 vaccine is available, and
  • Children younger than 9 years of age being vaccinated against influenza for the first time who still have not gotten their second recommended dose of vaccine.

Who Should Get Vaccinated?
In general, anyone 6 months of age or older who wants to reduce their chances of getting influenza can get vaccinated. However, it is recommended by ACIP that certain people should get vaccinated each year.

Vaccination for Children

Influenza vaccination is recommended for all children aged 6 months up to their 19th birthday.  The recommendation to vaccinate children 6 months up to their 5th birthday has been in place since 2006. These children should all be vaccinated annually.  In 2008, ACIP added children 5 years up to their 19th birthday and recommended that vaccination of these children begin before or during the 2008-09 influenza season if feasible, but no later than the 2009-10 influenza season.

Children and adolescents at higher risk for influenza complications should continue to be a focus of vaccination efforts as providers and programs transition to routinely vaccinating all children and adolescents.  Children under 6 months old are the pediatric group at highest risk of influenza complications, but they are too young to get an influenza vaccine. The best way to protect young children is to make sure members of their household and their caregivers are vaccinated.

Vaccination for Adults

Vaccination is especially important for people at higher risk of serious influenza complications or people who live with or care for people at higher risk for serious complications.
Persons working in health care settings also should be vaccinated annually against influenza. Vaccination of health care professionals has been associated with reduced work absenteeism and with fewer deaths among nursing home patients.

People recommended for vaccination based on their risk of complications from influenza or because they are in close contact with someone at higher risk of influenza complications include:

  • Children aged 6 months until their 5th birthday,
  • Pregnant women,
  • People 50 years of age and older,
  • People of any age with certain chronic health conditions (such as asthma, diabetes, or heart disease),
  • People who live in nursing homes and other long-term care facilities,
  • Household contacts of person at high risk for complications from influenza,
  • Household contacts and out of home caregivers of children less than 6 months of age, and
  • Health care workers.

People who should NOT be vaccinated include:

  • People who have a severe allergy to chicken eggs,
  • People who have had a severe reaction to an influenza vaccination,
  • People who have developed Guillian-Barré syndrome within 6 weeks of getting an influenza vaccine,
  • Children less than 6 months of age (influenza vaccine is not approved for this age group), and
  • People who have a moderate to severe illness with a fever (they should wait until they recover to get vaccinated).

Trivalent Inactivated Influenza Vaccine (TIV) Dosing and Side Effects

  • TIV is recommended for use in people 6 months and older, including those with high-risk conditions.
  • Children aged 6 months up to their 9th birthday who were vaccinated for the first time during the 2007–2008 influenza season but only received 1 dose during that season should receive 2 doses of the 2008–09 influenza vaccine. All other children aged 6 months up to their 9th birthday who have previously received 1 or more doses of influenza vaccine at any time should receive 1 dose of the 2008–09 influenza vaccine. Previously unvaccinated children aged 6 months up to their 9th birthday who only received a single vaccination during a season before 2007–08 should receive 1 dose of the 2008–09 influenza vaccine.
  • The viruses in the injectable influenza vaccine are inactivated so they do not cause influenza.
  • Minor side effects that can occur include soreness, redness or swelling at the injection site, fever (low grade), or aches. If these problems occur, they begin soon after vaccination and usually last 1 or 2 days.

Live, Attenuated Influenza Vaccine (LAIV) Dosing and Side Effects

    • LAIV is recommended for use in healthy* people 2-49 years of age who are not pregnant.
    • Children aged 2 years up to their 9th birthday who were vaccinated for the first time during the 2007–2008 influenza season but only received 1 dose during that season should receive 2 doses of the 2008–09 influenza vaccine. All other children aged 2 years to their 9th birthday who have previously received 1 or more doses of influenza vaccine at any time should receive 1 dose of the 2008–09 influenza vaccine. Previously unvaccinated children aged 2 years up to their 9th birthday who only received a single vaccination during a season before 2007–08 should receive 1 dose of the 2008–09 influenza vaccine.
    • LAIV is made from weakened viruses and does not cause influenza. The vaccine can cause mild illness in some people who get it.
    • In children, minor side effects can include runny nose or mild temporary wheezing. Occasionally headache, vomiting, muscle aches, or fever have been reported.
    • In adults, minor side effects can include runny nose, headache, sore throat, or cough.

* "Healthy" indicates persons who do not have an underlying medical condition that predisposes them to influenza complications.

 

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