Seasonal Influenza Vaccine Dosage & Administration

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

CDC recommends only preparing and drawing up vaccines just prior to administration. General-use syringes are designed for immediate administration—not for storage. Contamination and microorganism growth can occur in syringes with predrawn vaccine, especially with vaccine that does not contain a preservative. In addition, vaccine components may interact with polymers in a plastic syringe over time, potentially reducing vaccine potency.

As an alternative to predrawing vaccines, CDC recommends using manufacturer-filled syringes for large vaccination clinics.

However, if vaccine must be predrawn:

• Do not draw up vaccines before arriving at the clinic site. Drawing up doses days or even hours before a clinic is not acceptable.
• Each person administering vaccine should draw up no more than one multidose vial, or 10 doses, at one time.
• Monitor patient flow to avoid drawing up unnecessary doses.
• Discard any remaining vaccine in predrawn syringes at the end of the workday.
• If different vaccines (such as flu and pneumococcal vaccines) will be available, set up a separate administration station for each vaccine type to prevent medication errors.

Additional information on vaccine storage and handling can be found in CDC’s Vaccine Storage and Handling Toolkit.

What is the appropriate schedule for children?

Annual influenza vaccination is recommended for persons 6 months of age and older. Some children will need 2 doses of influenza vaccine in the same season. The following children will require 2 doses of influenza vaccine, administered at least 4 weeks apart, for the 2020–2021 season:

• Children 6 months through 8 years of age who have never received seasonal influenza vaccine or for whom vaccination history is unknown
• Children 6 months through 8 years of age who have not received at least 2 doses* of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2020

The following children will require 1 dose of influenza vaccine for the 2020–2021 season:

• Children 6 months through 8 years of age who have received at least 2 doses* of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2020
• Children 9 years of age and older

*Doses do not need to have been received during the same or consecutive influenza seasons.

What is the correct dosage (volume) of vaccine?

The amount of inactivated (injectable) vaccine that should be administered intramuscularly is based on the patient’s age and the vaccine product you are using.

• For children 6–35 months of age, the correct dosage (volume) is:
  • 0.25 mL for Afluria Quadrivalent
  • 0.5 mL for Fluarix Quadrivalent
  • 0.25 mL or 0.5 mL for Fluzone Quadrivalent
  • 0.5 mL for FluLaval Quadrivalent
• For persons 3 years of age and older, the correct dosage is 0.5 mL for most inactivated influenza vaccine products. Fluzone High-Dose Quadrivalent is for use in persons 65 years of age and older, and the correct dosage is 0.7 mL.

What is the recommended site and needle length for giving influenza vaccine to adults by intramuscular injection?

Decisions on needle size and injection site when administering vaccine by intramuscular injection must be made for each person based on size of the muscle, thickness of the fatty tissue at the injection site, and injection technique. For adults 19 years of age and older, the deltoid muscle in the upper arm is the preferred site, although the vastus lateralis muscle in the anterolateral thigh may be used if the deltoid site cannot be used. Influenza vaccines are not highly viscous, so a fine-gauge (22- to 25-gauge) needle can be used.

• Use a ⅝- to 1-inch needle for men and women who weigh less than 130 pounds (60 kg). Insert the needle at a 90-degree angle and stretch the skin flat between thumb and forefinger.
• Use a 1-inch needle for men and women who weigh 130–152 pounds (60–70 kg).
• Use a 1- to 1½-inch needle for women who weigh 152–200 pounds (70–90 kg) and men who weigh 152–260 pounds (70–118 kg).
• Use a 1½-inch needle for women who weigh more than 200 pounds (90 kg) and men who weigh more than 260 pounds (118 kg).

CDC has vaccine administration resources for clinicians administering influenza vaccine, including a needle length and gauge chart and demonstration videos for intramuscular injection and intranasal administration.

Additional information on vaccine administration and safe injection practices can be found in the following resources:

Epidemiology and Prevention of Vaccine-Preventable Diseases (the “Pink Book”), “Vaccine Administration” chapter (updated 11/2020)

ACIP General Best Practice Guidelines for Immunization

CDC Injection Safety

One and Only Campaign

Should I aspirate before injecting the vaccine?

No, because there are no large blood vessels in the recommended sites, aspiration (i.e., pulling back on the syringe plunger after needle insertion but before injection) is not necessary before injecting vaccines. The Advisory Committee on Immunization Practices’ General Best Practice Guidelines for Immunization state that aspiration is not required before administering a vaccine.

Can inactivated influenza vaccine be given at the same time as other vaccines, such as pneumococcal polysaccharide (PPSV23) or zoster (RZV) vaccines?

Yes — if other vaccines are indicated, they can be administered during the same clinical encounter as inactivated influenza vaccine. When giving several injections at a single visit, administer each vaccine at a separate injection site. The injection sites should be separated by 1 inch or more, if possible, so that any local reactions can be differentiated.

Can live, attenuated influenza vaccine be given at the same time as other vaccines?

Live, attenuated influenza vaccine may be administered simultaneously with other live or inactivated vaccines. However, if two live, attenuated vaccines (injectable and intranasal) are not given during the same clinical visit, they should be separated by at least 4 weeks (28 days) to minimize the potential risk for interference. For example, if live, attenuated influenza vaccine (LAIV) was given, at least 4 weeks should pass before MMR is administered.

What are the current recommendations for persons with egg allergies? Can they receive influenza vaccine?

The Advisory Committee on Immunization Practices has recently updated its recommendations for administering influenza vaccine to persons with egg allergies. The most current recommendations can be found at flu vaccine and people with egg allergies.

If an inactivated influenza vaccine approved for adult use is inadvertently administered to a child, is this considered a valid dose?

If an inactivated influenza formulation approved for adults is inadvertently administered to a child, this should be counted as a single valid dose for the child.  However, this is considered a vaccine administration error. Healthcare personnel should take steps to determine how the error occurred and put strategies in place to prevent it from happening in the future. In addition, we encourage providers to report all vaccine administration errors—even those not associated with an adverse event—to the Vaccine Adverse Event Reporting System (VAERS). A discussion of strategies to prevent errors can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (the “Pink Book”). Additional resources can be found on CDC’s vaccine administration web page.

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

Yes — if a formulation labeled for intramuscular injection is given by the subcutaneous or intradermal route, it should be repeated. The dose may be administered as soon as possible. There is no minimum interval required between the invalid dose (by subcutaneous or intradermal route) and the repeat dose.

Administering vaccine by the wrong route is considered a vaccine administration error. Healthcare personnel should take steps to determine how the error occurred and put strategies in place to prevent it from happening in the future.

In addition, we encourage providers to report all vaccine administration errors—even those not associated with an adverse event—to the Vaccine Adverse Event Reporting System (VAERS). A discussion of strategies to prevent errors can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (the “Pink Book”). Additional resources can be found on CDC’s vaccine administration web page.

A staff member inadvertently administered the wrong dosage (amount) of influenza vaccine. How do we correct this?

If a smaller than recommended dose (volume) of any inactivated influenza product is inadvertently administered, additional vaccine should be given so that the patient receives a full dose. The amount of vaccine that should be administered is based on when the patient is available to be revaccinated. For example:

• If a partial dose of an inactivated influenza vaccine product is administered and revaccination can occur on the same clinic day, the patient should receive a remaining volume to total the correct dosage. For example, if the correct dosage for the patient is 0.5 mL and they received only 0.25 mL, an additional 0.25 mL should be given (for a total of 0.5 mL) if revaccination can occur on the same day.
• If the patient cannot be revaccinated until the next day or later, a full dose of inactivated influenza vaccine should be administered as soon as the patient can return.
• If a larger dose (volume) of influenza vaccine is inadvertently administered, count the dose as valid. Revaccination with additional vaccine is not needed.

Giving an incorrect dose is considered a vaccine administration error. Healthcare personnel should take steps to determine how the error occurred and put strategies in place to prevent it from happening in the future.

In addition, we encourage providers to report all vaccine administration errors—even those not associated with an adverse event — to the Vaccine Adverse Event Reporting System (VAERS). A discussion of strategies to prevent errors can be found in the “Vaccine Administration” chapter of Epidemiology and Prevention of Vaccine-Preventable Diseases (the “Pink Book”). Additional resources can be found on CDC’s vaccine administration web page.

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