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Seasonal Influenza Vaccine Dosage & Administration

Questions & Answers

Can I pre-fill syringes for a flu shot clinic? If so, how long before the clinic can I pre-fill the syringes?

CDC does not recommend pre-filling syringes in the clinic because of the potential for administration errors. Exceptions include a mass vaccination clinic or a flu-specific vaccination clinic. We recommend not drawing up more than one vial or 10 doses at a time (whichever is less). The same person who draws vaccine should ideally be the person who administers it. Once the needle is placed on the syringe it should be used immediately. Any syringes except those filled by the manufacturer should be discarded at the end of the clinic day.

What is the appropriate dosing age for young children?

The following children will require 2 doses of influenza vaccine, administered at least 4 weeks apart, for 2015-16:

  • Children aged 6 months through 8 years who have never been vaccinated against influenza or for whom vaccination history is unknown;
  • Children who have not received at least two doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2015.

The following children will require only one dose of influenza vaccine for 2015-16:

  • Children 6 months through 8 years who have received at least two doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2015.
  • Children 9 years of age and older.

For inactivated (injectable) vaccine (IIV), the dose for children aged 6-35 months is 0.25 mL and the dose for children aged 36 months-9 years is 0.5 mL. For live attenuated vaccine (intranasal) (LAIV), the dose for all persons 2 years old and older is a 0.2 mL sprayer (0.1 mL in each nostril)

What length of needle should we use to give influenza vaccinations to adults?

A 1- to 1.5-inch needle should be used to give inactivated influenza vaccine intramuscularly to adults. Some experts recommend a 5/8 inch needle for adults who weigh less than 60 kg. For vaccination with the intradermal vaccine, the specifically designed microinjector has a 3/50 inch needle.

Does protection from seasonal influenza vaccine decline or wane within 3 or 4 months of vaccination? Should I wait until October or November to vaccinate my elderly or medically frail patients?

Antibody levels induced by vaccine decline post vaccination123. Although a 2008 literature review found no clear evidence of more rapid decline among older adults4, a 2010 study noted a statistically significant decline in antibody titers 6 months post vaccination among persons 65 years and older3. A case-control study conducted in Navarre, Spain, during the 2011–12 influenza season revealed a decline in vaccine effectiveness, primarily affecting persons 65 years and older5. While delaying vaccination might permit greater immunity later in the season, deferral might result in missed opportunities to vaccinate, as well as difficulties in vaccinating a population within a more constrained time period. Vaccination programs should balance maximizing the likelihood of persistence of vaccine-induced protection through the season with avoiding missed opportunities to vaccinate or vaccinating after influenza virus circulation begins.

If adult inactivated influenza vaccine is not available, can a high-risk adult or a high-risk child receive the pediatric product (thimerosal preservative-free 0.25 ml dose) as long as they are given 0.5ml?

If there is not an adequate supply of adult formulation, providers vaccinating high-risk individuals requiring 0.5mL of influenza vaccine when the provider has only the 0.25mL prefilled syringes of pediatric vaccine may choose to give two separate injections of the 0.25mL product to protect the high-risk individual. Providers should never attempt to transfer vaccine from one syringe to another for the purpose of administering only one injection.

Flu vaccine is available and recommended for almost everyone 6 months of age and older. If an adequate supply of adult formulation is available in the community, CDC does not recommend that providers combine two 0.25mL doses of pediatric influenza vaccine to vaccinate a single individual who requires a 0.5mL dose of vaccine. 

Should I repeat a dose of influenza vaccine administered by an incorrect route (such as intradermal)?

If a formulation labeled for intramuscular injection is given by the subcutaneous or intradermal route, it should not be counted.

Should I repeat a dose of influenza vaccine that is less than the recommended dose (0.25mL for children 6-35 months; 0.5mL for persons 36 months and older)?

If a dose of influenza vaccine is administered which is less than that specified in the package insert for that product and for the age of the recipient, it should NOT be counted as valid, and should be repeated.

  1. Ochiai H, Shibata M, Kamimura K, Niwayama S. Evaluation of the efficacy of split-product trivalent A(H1N1), A(H3N2), and B influenza vaccines: reactogenicity, immunogenicity and persistence of antibodies following two doses of vaccines. Microbiol Immunol 1986;30:1141–9.
  2. Künzel W, Glathe H, Engelmann H, Van Hoecke C. Kinetics of humoral antibody response to trivalent inactivated split influenza vaccine in subjects previously vaccinated or vaccinated for the first time. Vaccine 1996;14:1108–10.
  3. Song JY, Cheong HJ, Hwang IS, et al. Long-term immunogenicity of influenza vaccine among the elderly: Risk factors for poor immune response and persistence. Vaccine 2010;28:3929–35.
  4. Skowronski DM, Tweed SA, De Serres G. Rapid decline of influenza vaccine-induced antibody in the elderly: is it real, or is it relevant? J Infect Dis 2008;197:490–502.
  5. Castilla J, Martínez-Baz I, Martínez-Artola V, et al.; Primary Health Care Sentinel Network; Network for Influenza Surveillance in Hospitals of Navarre. Decline in influenza vaccine effectiveness with time after vaccination, Navarre, Spain, season 2011/12. Euro Surveill 2013;18:20388.