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) [51KB, 2 pages]
  • Live, Intranasal Influenza Vaccine (LAIV) [48KB, 2 pages]
• 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?

2010-11 flu vaccine shipments have begun. Doctors and nurses are encouraged to begin vaccinating their patients as soon as flu vaccine is available in their area, even as early as August, and continue vaccinating through the remainder of the flu season. 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?

Vaccine shipments have already begun, so vaccination should begin as soon as flu vaccine is delivered to their location. Flu vaccines 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 might 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 2010-11 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?

On February 24, 2010 vaccine experts voted that everyone 6 months and older should get a flu vaccine each year starting with the 2010-2011 influenza season. While everyone should get a flu vaccine each flu season, ita??s especially important that certain people get vaccinated either because they are at high risk of having serious flu-related complications or because they live with or care for people at high risk for developing flu-related complications.

Vaccination for Children

Influenza vaccination is recommended for all children aged 6 months up to their 19th birthday.

All children 6 months through 8 years of age are recommended to receive 2 doses of 2010-11 flu vaccine 4 or more weeks apart unless they have received:

1. at least 1 dose of 2009 H1N1 vaccine last flu season, and
2. at least 1 dose of seasonal vaccine prior to the 2009-2010 flu season or 2 doses of 2009-10 seasonal flu vaccine
   
   If a child has fulfilled both requirements, they only need 1 2010-11 flu vaccine.

The first dose should be given as soon as vaccine becomes available, and the second dose should be given 28 more days after the first dose. The first dose "primes" the immune system; the second dose provides immune protection. Children who only get one dose but need two doses can have reduced or no protection from a single dose of flu vaccine. Two doses are necessary to protect these children. If your child needs the two doses, begin the process early, so that children are protected before influenza starts circulating in your community. Be sure to follow up to get your child a second dose if they need one. It usually takes about two weeks after the second dose for protection to begin.

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

Everyone 6 months of age and older are recommended to get the flu vaccine, which includes even the healthiest 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-Barr?? 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.
• All children 6 months through 8 years of age are recommended to receive 2 doses of 2010-11 flu vaccine 4 or more weeks apart unless they have received:
  1. at least 1 dose of 2009 H1N1 vaccine last flu season, and
  2. at least 1 dose of seasonal vaccine prior to the 2009-2010 flu season or 2 doses of 2009-10 seasonal flu vaccine
     If a child has fulfilled both requirements, they only need 1 2010-11 flu 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.
• All children 2 years through 8 years of age are recommended to receive 2 doses of 2010-11 flu vaccine 4 or more weeks apart unless they have received:
  1. at least 1 dose of 2009 H1N1 vaccine last flu season, and
  2. at least 1 dose of seasonal vaccine prior to the 2009-2010 flu season or 2 doses of 2009-10 seasonal flu vaccine
     
     If a child has fulfilled both requirements, they only need 1 2010-11 flu 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.