Parents may be more excited this year to have their child vaccinated against influenza. This is not only because influenza vaccine will prevent serious medical complications of influenza disease, but because it is one more way to prevent even mild symptoms of influenza at a time when every febrile illness presents families with logistical complications (e.g., COVID-19 testing, home schooling during quarantine).

The updated influenza vaccination recommendations were published in the August 27, 2021, issue of the Morbidity and Mortality Weekly Report (MMWR) with a significant amount of information to absorb. To test yourself on your influenza vaccination knowledge, try to answer each of the following questions.

Question 1

In September, on his 6-month birthday, Teddy presents to your office for routine vaccination. Which of the following are TRUE?

  1. You should hold off on influenza vaccination until the end of October, so Teddy will have higher antibody concentrations when influenza incidence peaks in the U.S.
  2. Your office stocks Afluria® (Seqirus), so you should give Teddy 0.25 milliliters (ml) IM.
  3. Teddy’s mother refuses vaccines that contain thimerosal, so there is only one brand of influenza vaccine that he can receive.
  4. If Teddy had a history of hives and recurrent vomiting after exposure to eggs, influenza vaccination would be contraindicated for him.

Answer to question 1

Only answer B is true. The correct dose for Afluria is 0.25 ml. Dosing for patients ages 6 through 35 months is 0.5 ml intramuscularly (IM) for all injectable influenza vaccines in the U.S. except Afluria (Seqirus; 0.25 mL) and Fluzone® (Sanofi Pasteur; 0.25 mL or 0.5 mL, although the 0.25-ml prefilled syringes are not expected to be available for the 2021–22 influenza season).

Here is why the other answers are false:

  1. Give the first dose ASAP! Children who need two doses (children aged 6 months through 8 years who have never received influenza vaccine or who have not previously received a lifetime total of ≥ 2 doses) should receive their first dose as soon as possible when the vaccine becomes available. This will allow the second dose (which must be given at least 4 weeks after the first) to be received by the end of October. 
  2. True.
  3. Many influenza vaccines are now thimerosal-free. In the U.S., influenza vaccines supplied in a prefilled syringe or a single-dose vial are all mercury-free. Thimerosal is a preservative used only in multi-dose vials of influenza vaccine.
  4. Teddy could receive influenza vaccine despite his reaction to eggs. Having a history of egg-related reactions — even if they required emergency medical intervention — is not, in and of itself, a contraindication to influenza vaccination. However, if the individual’s reaction involves more than just development of hives and an egg-free version (ccIIV4* or RIV4**) is not available, the vaccine should be administered in a medical setting under the supervision of a healthcare provider equipped to respond to a severe allergic reaction.

*Cell culture–based inactivated influenza vaccine (ccIIV4)

** Recombinant influenza vaccine (RIV4)

Question 2

Riley, age 17 years, presented in the clinic this September for influenza vaccination. Riley has a history of anaphylaxis following receipt of ccIIV4. Which of the following are TRUE?

  1. All of the influenza vaccines available in the U.S. this year are quadrivalent, containing hemagglutinin derived from two influenza A viruses and two influenza B viruses.
  2. Riley’s history of anaphylaxis following receipt of ccIIV4 is a contraindication to receipt of future doses of ccIIV4, all egg-based inactivated influenza vaccines (IIV), and the live, attenuated (nasal spray) influenza vaccine (LAIV), but not to RIV.
  3. Riley is eligible for COVID-19 vaccine today. She may be given both vaccines at the same visit, but they should be administered in separate anatomic sites.
  4. For an adolescent, influenza vaccination should have been withheld during July and August unless there was a concern that vaccination at a later time might not be possible.

Answers to question 2

Answers A, B, and C are true. Here is why:

  1. This year, the influenza vaccines are all quadrivalent with two influenza A strains and two influenza B strains.
  2. For ccIIV4, a history of severe allergic reaction (e.g., anaphylaxis) to any cell-culture-based inactivated influenza vaccine (ccIIV), regardless of valency, or to any component of ccIIV4 is a contraindication to future receipt. Riley’s history would also be a contraindication to the use of egg-based IIVs and LAIV. However, this history is only a precaution for receipt of RIV.
  3. COVID-19 and influenza vaccines may be given at the same visit, but they should be administered in separate anatomic sites. Get additional details about recommendations for the use of COVID-19 vaccines and additional clinical guidance.

Answer D was false. Children of any age who require only one dose for the season may be vaccinated as soon as vaccine is available. Waning immunity among children has not been identified to be as much of a concern as it is for adults.

Question 3

Your influenza vaccine supply arrived in August this year. Each of the following patients attends their scheduled appointments faithfully. Which of them should have been vaccinated during their August visit?

  1. Age 21, healthy, first trimester of pregnancy
  2. Age 21, healthy, third trimester of pregnancy
  3. Age 51, diagnosed with insulin-dependent diabetes
  4. Age 71, healthy

Answers to question 3

The pregnant patient in answer “B” is the only one who should have been vaccinated in August. While pregnant individuals in any trimester may receive influenza vaccine, the CDC recommends that those in their third trimester receive influenza vaccine early, i.e., in July or August. In this manner, maternal antibodies, passively transferred before birth, can help protect the baby against influenza in the months after birth, but before infant vaccination.

CDC states, “For nonpregnant adults, vaccination in July and August should be avoided unless there is concern that later vaccination might not be possible.” The current recommendation is to start vaccinating all nonpregnant adults in September with the goal of having everyone vaccinated by the end of October. Giving influenza vaccination during this window (rather than in July or August) might result in greater immunity later in the season while still giving adults time to receive the vaccine before arrival of the virus in the United States. We should expect a similar timing recommendation in future years.

Question 4

Assume that your healthcare facility is mandating influenza vaccine. Which of the following reasons for declining vaccination is based on evidence?

  1. “I am allergic to eggs.”
  2. “The flu shot gives me the flu.”
  3. “I won’t take the flu shot because it is made with fetal cells.”
  4. None of these

Answers to question 4

Answer “D” is correct: None of these statements are based on recommendations or scientific facts.

  1. As mentioned earlier, individuals with a history of egg-involving reactions can receive any licensed, recommended influenza vaccine that is otherwise appropriate for their age and health status.
  2. All flu vaccines given as a shot contain dead influenza virus or individual proteins, so they cannot cause an infection. While the nasal vaccine (LAIV) contains live, weakened influenza viruses, they have been altered, so that they can reproduce in the temperatures of the nose, but not the lungs. Therefore, they cannot cause influenza either.
  3. Influenza vaccines are not made using, nor do they contain, fetal cells. (For more information, see the VEC’s webpage, “Vaccine Ingredients – Fetal Cells”).

You would think it could go without saying, “Be sure all healthcare personnel in your circle of influence are vaccinated and understand why influenza vaccination is important.” But, it cannot. Often people who work in healthcare have the same unscientific misunderstandings that the public has, and the corrosive effect of their inaccurate statements spreads like … well, like influenza.

Additional helpful web links

Materials in this section are updated as new information and vaccines become available. The Vaccine Education Center staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family's personal health. You should not use it to replace any relationship with a physician or other qualified healthcare professional. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult your physician or, in serious cases, seek immediate assistance from emergency personnel.