Last reviewed:
October 11, 2026
CDC discourages the practice of prefilling vaccine into syringes for several reasons, including:
- The increased possibility of administration and dosing errors
- The increased risk of inappropriate storage temperature
- The probability of bacterial contamination
- The probability of reducing the vaccine’s potency over time
Prefilling vaccine into syringes also violates basic medication administration guidelines, which state that an individual should administer only those medications he or she has prepared and drawn up.
Although pre-drawing vaccine is discouraged, a limited amount of vaccine may be pre-drawn in a mass vaccination clinic setting under the following conditions:
- Only a single type of vaccine (for example, influenza) is administered at the mass vaccination clinic setting
- Vaccine is not drawn up in advance of its arrival at the mass vaccination clinic site
- These pre-drawn syringes are stored at temperatures appropriate for the vaccine
- No more than 1 vial or 10 doses (whichever is greater) is drawn into syringes
- Clinic staff monitor patient flow carefully and avoid drawing up unnecessary doses or delaying administration of pre-drawn doses
At the end of the clinic day, all remaining vaccine in syringes prefilled by staff should be discarded.
Vaccination clinic staff seeking to increase their speed and efficiency may consider using formulations packaged in manufacturer-filled syringes (MFS).
Last reviewed:
October 11, 2026
Vaccinating people against influenza who have recently tested positive for COVID-19 involves multiple considerations, such as whether vaccinating them could expose others to COVID-19, how sick they are, their risk for severe influenza illness, the ability to vaccinate at a later date, and the desire to avoid confusing postvaccination symptoms with those of COVID-19. Usually, people who are known to be infectious should not be brought to a vaccination setting if doing so could expose others to COVID-19. Any moderate or severe acute illness is a precaution to influenza vaccination: vaccination should generally be deferred until recovery. For people with mild or asymptomatic COVID-19, delaying vaccination also might be considered to avoid confusing COVID-19 symptoms with postvaccination reactions.
Last reviewed:
October 11, 2026
Inactivated and recombinant influenza vaccines are not known to cause false positive nasal swab tests. The results may indicate real infections; however, false positive test results are possible with rapid tests, and these are more likely to occur if the tests are done when influenza prevalence in the area is low, such as early in the influenza season. For more information regarding interpretation of rapid influenza tests see www.cdc.gov/flu/professionals/diagnosis/rapidlab.htm.
Last reviewed:
October 11, 2026
Injectable influenza vaccines should be administered intramuscularly. IIV should be administered in the anterolateral thigh muscle of an infant or young child. IIV, RIV, and mFlusiva should be administered in the deltoid muscle of an older child, adolescent, or adult; the anterolateral thigh may be used if necessary. Immunize.org’s administration guide is available at www.immunize.org/catg.d/p2020.pdf.
Last reviewed:
October 11, 2026
This is not an acceptable practice. Doses of influenza vaccine (or any other vaccine) should never be split into “half doses.” If a “half dose” is administered, it should not be accepted as a valid dose. The second half of the dose may be administered if the error is caught and corrected on the same day; if not, repeat the vaccination on a different day as soon as possible with a full age-appropriate dose.
Last reviewed:
October 11, 2026
Yes. Syncope may occur following any vaccination. It is prudent for all people to be observed for syncope for at least 15 minutes after any vaccination. Immunize.org has a 1-page resource for healthcare professionals that summarizes ways to reduce the risk of post-vaccination syncope: www.immunize.org/wp-content/uploads/catg.d/p4260.pdf.
Last reviewed:
October 11, 2026
Low-dead-space syringes can reduce vaccine wastage. In 2026–27 only a small quantity of Fluzone (Sanofi) is available in a 5.0 mL multidose vial. Follow the manufacturer’s package insert for the number of doses that may be withdrawn.
Last reviewed:
October 11, 2026
No. Only the number of doses indicated in the manufacturer’s package insert should be withdrawn. For a 5.0 mL multidose vial of Fluzone, this is 10 doses. After the maximum number of doses has been withdrawn, discard the vial even if vaccine remains and the expiration date has not been reached.
Last reviewed:
October 11, 2026
RIV is not licensed for people younger than 9 years of age, so there are no data regarding safety and efficacy in this age group. However, no serious side effects would be expected. The dose does not need to be repeated and should be considered valid. Even if no adverse reaction occurs, vaccine administration errors like this should be reported to the Vaccine Adverse Events Reporting System (VAERS) at www.vaers.hhs.gov.
Last reviewed:
October 11, 2026
If the error is discovered on the same clinic day, administer the remaining 0.25 mL of FluLaval that day. If it cannot be corrected that day, do not count the partial dose. Recall the child as soon as possible and administer a full age-appropriate dose of FluLaval, Fluarix, Fluzone, or Flucelvax.
Last reviewed:
October 11, 2026
