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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 because of the potential for administration errors. 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 full protection:

  • Children aged 6 months to 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 vaccine and at least one dose of pandemic 2009(H1N1)-containing vaccine previously;
  • Children who have received at least two doses of seasonal vaccine and at least one dose of pandemic 2009(H1N1) vaccine previously will need only one dose this season. ACIP has developed an algorithm that might be helpful in determining the number of doses needed.

Children 6 months through 8 years who have received at least two doses of seasonal vaccine and at least one dose of pandemic 2009(H1N1) vaccine previously will need only one dose this season. Children 9 years of age and older need only one dose this season.

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

CDC recommends that seasonal influenza vaccine be administered ideally by October. Antibody to seasonal inactivated influenza vaccine does decline in the months following vaccination, but experts believe that it is still high enough to provide protection to the end of the season. A recent review concluded that there was no evidence that antibody-induced immune response decreased faster in the elderly than in young adults.

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 still 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.

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

If the dose (amount) of vaccine was age-appropriate, it can be counted as valid if given by the subcutaneous route. If an intramuscular formulation is given by the 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 less than an age-appropriate dose of influenza vaccine is administered it should NOT be counted as valid regardless of the route it was given, and should be repeated.