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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 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 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 immunization clinics.

However, if vaccine must be predrawn:

  • Set up a separate administration station for each vaccine type to prevent medication errors.
  • 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 vaccines 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.

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

What is the appropriate dosing age for young 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 2016–17 season:

  • Children aged 6 months through 8 years who have never been vaccinated against influenza or for whom vaccination history is unknown
  • Children aged 6 months through 8 years who have not received at least 2 doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2016

The following children will require 1 dose of influenza vaccine for 2016–17:

  • Children 6 months through 8 years who have received at least 2 doses of seasonal influenza vaccine (trivalent or quadrivalent) before July 1, 2016
  • Children 9 years of age and older

What is the correct dose (volume) of vaccine?

The amount of inactivated (injectable, intramuscular) vaccine that should be administered is based on the age of the patient.

  • The dose for children 6-35 months of age is 0.25 mL.
  • The dose for persons 3 years of age and older is 0.5 mL.

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

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 (less than 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 (more than 90 kg) or men who weigh more than 260 pounds (more than 118 kg).

Additional information on vaccine administration and safe injection practices can be found at: 

Epidemiology and Prevention of Vaccine-Preventable Diseases (the Pink Book), Vaccine Administration chapter

General Recommendations on Immunization, Recommendations of the Advisory Committee on Immunization Practices (ACIP) [PDF - 943 KB, 64 pages]

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 Recommendations on 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 zoster (HZV), pneumococcal polysaccharide (PPSV23), or pneumococcal conjugate (PCV13) 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.  Please note that pneumococcal conjugate (PCV13 [Prevnar®]) and pneumococcal polysaccharide (PPSV23 [Pneumovax®]) vaccines should NOT be administered at the same time.  A helpful job aid for scheduling these vaccines can be found at Pneumococcal Vaccine Timing for Adults [PDF - 87.8 KB].

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 on administering influenza vaccine to persons with egg allergies.  The most current recommendations can be found at flu vaccine and people with egg allergies.

If inactivated influenza vaccine presentations for persons 3 years of age and older are not available, can a high-risk older child or adult receive the pediatric product (thimerosal preservative-free 0.25 ml dose) as long as they are given 0.5 mL?

Flu vaccine is available and recommended for almost everyone 6 months of age and older. If an adequate supply of adult formulation is available, CDC does not recommend that providers use pediatric formulations to vaccinate adults.

If there is not an adequate supply of adult formulation, providers may choose to administer pediatric presentations such as manufacturer-filled syringes (0.25 mL). Two manufacturer-filled syringes (0.25 mL) are needed to provide the correct dose (0.5 mL) for persons 3 years of age and older. Two separate injections should be administered. Providers should never attempt to transfer vaccine from one syringe to another for the purpose of administering only one injection.  This is considered off-label use.

Should I repeat a dose of 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.

A staff member inadvertently administered the wrong dose of influenza vaccine. How do we correct this?

If you give less than a full age-appropriate dose of influenza vaccine, the dose should be repeated. You should revaccinate the person with the age-appropriate dose as soon as possible. If a pediatric vaccine dose (0.25 mL) is administered inadvertently to an adult, an additional pediatric dose (0.25 mL) should be administered on the same clinic day to provide a full adult dose (0.5 mL).  If the error is discovered later, an adult dose should be administered as soon as the patient can return.

If you give more than an age-appropriate dose, count the dose as valid and notify the patient/parent about the error.  When an error occurs, immunization providers should take steps to determine how the error occurred and put strategies in place to prevent it from happening in the future.

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