Issue 1,590: September 21, 2021
Ask the Experts: IAC Answers Questions about Influenza Vaccination for the 2021–22 Season
As an additional service to IAC Express readers, we periodically publish special editions such as this one, providing you with new and updated Ask the Experts questions and answers from IAC experts. This issue includes 16 Q&As about influenza vaccination based on recently updated ACIP recommendations.
To find the full set of IAC’s Ask the Experts influenza vaccination Q&As, visit www.immunize.org/askexperts/experts_inf.asp.
You can find all of these questions and answers, plus more than a thousand others about vaccines and vaccine administration, on our "Ask the Experts" gateway page at www.immunize.org/askexperts.
IAC's team of experts includes Kelly L. Moore, MD, MPH (team lead) and Carolyn B. Bridges, MD, FACP.
Influenza Vaccination Questions for the 2021–22 Season
Influenza Vaccination Questions & Answers for the 2021–22 Season
Q: Please summarize what’s new in the 2021–22 influenza vaccine recommendations.
A: Yearly influenza vaccination continues to be recommended for everyone age 6 months and older. All available influenza vaccines in the United States are now quadrivalent (containing two influenza A and two influenza B strains). The 2021–22 vaccines have been updated to include new influenza A (H3N2) and influenza A (H1N1) virus vaccine antigens. One vaccine product, Flucelvax Quadrivalent (ccIIV4, Seqirus) is now FDA-approved for children age 2 years and older (formerly approved for children age 4 years and older).
In addition, the 2021–22 recommendations discuss considerations for co-administration of influenza vaccine with a COVID-19 vaccine. Influenza vaccines and other vaccines may be administered at the same time as a COVID-19 vaccine. Guidance on COVID-19 vaccination, including coadministration with other vaccines, is available here: www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html. If administered simultaneously, COVID-19 vaccines and influenza vaccines that might be more likely to cause a local reaction [e.g., adjuvanted inactivated influenza vaccine (aIIV4, Fluad Quadrivalent, Seqirus) or high-dose inactivated vaccine (HD-IIV4 Fluzone High-Dose Quadrivalent (Sanofi Pasteur)] should be administered in different limbs, if possible].
CDC also now recommends that providers consider influenza vaccination of pregnant people in their third trimester as soon as vaccine is available. CDC continues to recommend that children not previously vaccinated who need two doses of influenza receive their first dose as soon as possible so that they can get their second dose before the end of October. The two doses should be separated by at least 4 weeks. For non-pregnant adults, CDC continues to recommend avoiding influenza vaccination in July and August unless there is a concern that later vaccination may not be possible.
Lastly, CDC revised guidance for the contraindications and precautions for the use of Flucelvax Quadrivalent (ccIIV4) and Flublok Quadrivalent (RIV4, Sanofi Pasteur) among people with a history of a severe allergic reaction to an influenza vaccine. For ccIIV4, a history of a severe allergic reaction to a prior dose of any egg-based IIV, live attenuated vaccine (LAIV), or RIV is a precaution. For RIV4, a history of a severe allergic reaction to IIV, LAIV, or ccIIV4 is a precaution. People with precautions for receiving ccIIV4 and RIV4 should be vaccinated in a medical setting under supervision of a provider who can recognize and manage severe allergic reactions. RIV4 continues to be contraindicated for people with a prior allergic reaction to any RIV vaccine components. Similarly, ccIIV4 is contraindicated for people with a prior allergic reaction to any ccIIV components.
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Q: Which influenza vaccines will be available during the 2021–22 influenza season?
A: Multiple manufacturers are producing influenza vaccine for the U.S. market for the 2021–22 season. Inactivated influenza vaccines (IIV4) will be produced using egg-based, cell culture-based, and recombinant technologies. Live attenuated nasal spray vaccine (LAIV4, Flumist Quadrivalent; AstraZeneca) will also be available. All influenza vaccines are quadrivalent (containing four strains of influenza virus).
Influenza vaccines are not all licensed for the same age groups. ACIP does not state a preference for one influenza vaccine over another for people for whom more than one vaccine is recommended and appropriate.
IAC has a handout that summarizes each of the products available for the current influenza vaccination season at www.immunize.org/catg.d/p4072.pdf.
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Q: What are the vaccine viruses for the 2021–22 influenza season?
A: Vaccine viruses differ by the type of vaccine, but they are designed to protect against the same strains of circulating viruses. For the 2021–22 season, U.S. egg-based influenza vaccines (i.e., vaccines other than ccIIV4 and RIV4) will contain hemagglutinin (HA) derived from:
- an influenza A/Victoria/2570/2019 (H1N1)pdm09-like virus [new];
- an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus [new];
- an influenza B/Washington/02/2019 (Victoria lineage)-like virus; and
- an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
For the 2021–22 season, U.S. cell culture–based inactivated (ccIIV4) and recombinant (RIV4) influenza vaccines will contain HA derived from:
- an influenza A/Wisconsin/588/2019 (H1N1)pdm09-like virus [new];
- an influenza A/Cambodia/e0826360/2020 (H3N2)-like virus [new];
- an influenza B/Washington/02/2019 (Victoria lineage)-like virus; and
- an influenza B/Phuket/3073/2013 (Yamagata lineage)-like virus.
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Q: When does CDC recommend starting influenza vaccination?
A: For most people, vaccination should begin in September and, ideally, be done by the end of October.
There are two groups of people for whom CDC recommends vaccination as soon as vaccine becomes available: pregnant people in the third trimester and children who need two doses of vaccine this season. Vaccination during pregnancy has been shown to reduce influenza-related hospitalizations during early infancy as a result of maternal antibodies passed to the fetus. Pregnant people in their third trimester are recommended to be vaccinated as soon as vaccine is available in order to allow time for some vaccine-induced protection to be passed to the fetus. Other pregnant people should be vaccinated by the end of October.
CDC continues to recommend that children not previously vaccinated who need two doses of influenza receive their first dose as soon as vaccine is available so that they can get their second dose before the end of October.
For nonpregnant adults, influenza vaccination during July and August should be avoided unless there is concern that later vaccination might not be possible. Early vaccination has been associated with decreased vaccine effectiveness before the end of the influenza season, particularly among older adults.
CDC recommends that influenza vaccination be offered by the end of October. This balances considerations regarding the unpredictability of timing of onset of the influenza season and concerns that vaccine-induced immunity might wane over the course of a season, particularly for older adults.
For people not vaccinated by the end of October, vaccination efforts should continue throughout the season, even after influenza activity has begun.
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Q: Since influenza virus circulation was very limited during the 2020–21 influenza season, what might be expected for the 2021–22 influenza season?
A: The timing and severity of influenza seasons are always unpredictable. Influenza viruses circulated at low levels in 2020–21 while measures to prevent the spread of COVID-19 were widely adopted, including social distancing, mask wearing, and reduction in travel. As the use of these COVID-19 mitigation measures has decreased, increases in the circulation of other non-influenza respiratory viruses have occurred. Thus, it is likely that influenza virus circulation will also increase during 2021–22. Current information on non-influenza respiratory viruses can be found at www.cdc.gov/surveillance/nrevss/index.html. Current information on influenza virus circulation can be found at www.cdc.gov/flu/weekly/index.htm.
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Q: May influenza vaccines be given at the same time as other vaccines, including COVID-19 vaccines?
A: Yes. CDC’s clinical guidance for the use of COVID-19 vaccines states that any vaccine may be given on the same day or any day before or after COVID-19 vaccination, at a different anatomic site. According to the CDC’s “General Best Practice Guidelines for Immunization,” simultaneously administering all vaccines for which a person is eligible at the time of a visit increases the probability that a person will be fully vaccinated by the appropriate time. If administered at the same time, COVID-19 vaccines and influenza vaccines that might be more likely to cause a local reaction (aIIV4 or HD-IIV4) should be administered in separate limbs, if possible.
Because CDC guidance on COVID-19 vaccination is updated as new information emerges, periodically check the CDC website for updates to ACIP recommendations on the use of COVID-19 vaccine (www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/covid-19.html) and updates to CDC’s interim clinical guidance for the use of COVID-19 vaccines (www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html).
IIV and RIV can be administered on the same day or any other day before or after other live or inactivated vaccines. Injectable vaccines should be administered in separate anatomic sites when given on the same day.
LAIV may be given on the same day as any other live or inactivated vaccines. However, if two live vaccines are not given on the same day, they should be separated by at least 4 weeks.
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Q: What influenza vaccines are available for children for the 2021–22 influenza season?
A: Four egg-based quadrivalent inactivated influenza vaccines (IIV4s), all given as intramuscular injections, are available for children age 6 months and older:
- Afluria Quadrivalent (Seqirus): 0.25 mL/dose for age 6 through 35 months; 0.5 mL/dose for age 3 years and older
- Fluarix Quadrivalent (GlaxoSmithKline): 0.5 mL/dose for age 6 months and older
- FluLaval Quadrivalent (GlaxoSmithKline): 0.5 mL/dose for age 6 months and older
- Fluzone Quadrivalent (Sanofi Pasteur): 0.25 mL or 0.5 mL per dose for age 6 through 35 months; 0.5 mL/dose age 3 years and older
Flucelvax Quadrivalent (ccIIV4, Seqirus): 0.5 mL/dose given intramuscularly, is available for children age 2 years and older.
Flumist Quadrivalent (LAIV4, AstraZeneca): 0.2 mL administered intranasally (0.1 mL in each nostril), is available for healthy, non-pregnant children age 2 years and older.
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Q: What influenza vaccines are available for adults?
A: Four egg-based quadrivalent standard dose IIV vaccines (SD-IIV4s), all given as intramuscular injections, are available for adults of all ages:
- Afluria Quadrivalent (Seqirus): 0.5 mL/dose
- Fluarix Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
- FluLaval Quadrivalent (GlaxoSmithKline): 0.5 mL/dose
- Fluzone Quadrivalent (Sanofi Pasteur): 0.5 mL/dose
Flublok Quadrivalent (RIV4, Sanofi Pasteur): 0.5 mL/dose given intramuscularly is available for all adults age 18 years and older.
Flumist Quadrivalent (LAIV4, AstraZeneca): 0.2 mL administered intranasally (0.1 mL in each nostril), is available for healthy, non-pregnant adults through age 49 years.
Fluzone High-Dose Quadrivalent (egg-based HD-IIV4, Sanofi Pasteur): 0.7 mL administered intramuscularly, is available for adults age 65 years and older.
Fluad Quadrivalent (egg-based aIIV4, Seqirus): 0.5 mL administered intramuscularly, is available for adults age 65 years and older.
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Q: Which children younger than age 9 years will need 2 doses of influenza vaccine in this influenza season?
A: Children age 6 months through 8 years should receive a second dose 4 weeks or more after the first dose 1) if they are receiving influenza vaccine for the first time, 2) if they have not received a total of at least two doses of any seasonal influenza vaccine before July 1 of the current year, or 3) if their vaccination history is unknown. The two previous doses need not have been received during the same season or consecutive seasons.
Children who are 8 years old and are recommended to receive two doses during the current season but who have a 9th birthday during the current season before receiving dose 2 should still receive dose 2.
IAC's handout titled "Guide for Determining the Number of Doses of Influenza Vaccine to Give to Children Age 6 Months Through 8 Years" provides additional guidance on this issue; it is available at www.immunize.org/catg.d/p3093.pdf.
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Q: What is the ACIP guidance on influenza vaccination and egg allergy?
A: ACIP recommends that people with a history of egg allergy who have experienced only hives after exposure to egg should receive influenza vaccine without specific precautions (except the standard 15-minute post-vaccination observation period for syncope). Any age-appropriate vaccine may be used.
For people who report having had an anaphylactic reaction to egg (more severe than hives), if a vaccine other than Flucelvax Quadrivalent (ccIIV4, Seqirus) or Flublok Quadrivalent (RIV4, Sanofi Pasteur) is given, the vaccine should be administered in an inpatient or outpatient medical setting supervised by a healthcare provider who is able to recognize and manage severe allergic conditions. Although not specifically recommended by ACIP, providers may prefer administering an age-appropriate egg-free vaccine (ccIIV4 or RIV4) for patients with severe egg allergy.
A previous severe allergic reaction to influenza vaccine, regardless of the component suspected to be responsible for the reaction, is a contraindication to future receipt of the vaccine. For a complete list of vaccine components (i.e., excipients and culture media) used in the production of the vaccine, check the package insert (available at www.immunize.org/fda) or go to www.cdc.gov/vaccines/pubs/pinkbook/downloads/appendices/B/excipient-table-2.pdf.
For more details about giving influenza vaccine to people with a history of egg allergy, see page 14 of the 2021–2022 ACIP influenza vaccine recommendation at www.cdc.gov/mmwr/volumes/70/rr/pdfs/rr7005a1-H.pdf. You also may find the IAC handout "Influenza Vaccination of People with a History of Egg Allergy" helpful (see www.immunize.org/catg.d/p3094.pdf).
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Q: What are the contraindications and precautions for people with a history of a severe allergic reaction to a previous influenza vaccination?
A: A severe allergic reaction to any influenza vaccine is a contraindication to receiving additional doses of the same vaccine or receiving any egg-based influenza vaccines. The following table summarizes the contraindications and precautions for different types of influenza vaccine and is adapted from table 3 on page 5 of the 2021–22 influenza ACIP recommendations at www.cdc.gov/mmwr/volumes/70/rr/pdfs/rr7005a1-H.pdf:
| Vaccine (of any valency) associated with previous serious or anaphylactic reaction |
Available 2021–22 influenza vaccines |
| |
Egg-based IIV4s and LAIV4 |
ccIIV4 |
RIV4 |
| Any egg-based IIV or LAIV |
Contraindication |
Precaution† |
Precaution† |
| Any ccIIV |
Contraindication |
Contraindication |
Precaution† |
| Any RIV |
Contraindication |
Precaution† |
Contraindication |
| Unknown influenza vaccine |
Allergist consultation recommended |
†Note regarding patients having either of the above precautions for either ccIIV or IIV: Use of ccIIV4 and RIV4 in such instances should occur in an inpatient or outpatient medical setting under the supervision of a healthcare provider (HCP) who can recognize and manage severe allergic reaction; HCPs can also consider consulting with an allergist to help identify the vaccine component responsible for the reaction.
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Q: What types of personal protective equipment do healthcare personnel need for administering vaccines in light of COVID-19?
A: CDC recommends that healthcare personnel administering any vaccines during COVID-19 wear surgical masks. N95 respirators are not recommended. Eye protection is recommended in areas with moderate or substantial community COVID-19 transmission; it is optional in communities with minimal or no COVID-19 transmission. Gloves are recommended when giving intranasal or oral vaccines because of the increased likelihood of coming into contact with a patient’s mucous membranes and body fluids. Gloves are optional for other vaccines. Importantly, hands should be washed and gloves, when worn, should be changed between each patient. For additional details, visit the CDC web page “Interim Guidance for Routine and Influenza Immunization Services During the COVID-19 Pandemic” at www.cdc.gov/vaccines/pandemic-guidance/index.html or IAC’s handout, “Protective Measures for Vaccinating during the Pandemic,” available at https://immunize.org/catg.d/p2009.pdf.
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Q: Where can I find resources to help me plan mass vaccination clinics for influenza or COVID-19 vaccines?
A: Multiple resources are available on the CDC website at: www.cdc.gov/vaccines/hcp/admin/mass-clinic-activities/index.html and at IAC’s “Mass Vaccination Resources” website at: www.mass-vaccination-resources.org.
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Q: Is it acceptable to draw up vaccine into syringes at the beginning of the day? If it isn't, how much in advance can this be done?
A: 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-immunization clinic setting under the following conditions:
- Only a single type of vaccine (for example, influenza) is administered at the mass-immunization 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 they hold
- 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.
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Q: What are CDC recommendations for influenza vaccination of people who have already become ill with influenza during the season?
A: Because more than one type or subtype of influenza virus can circulate in any given influenza season, providers should offer influenza vaccination to unvaccinated people throughout the influenza season, including people who may have had an influenza illness already in the season.
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Q: Can people who are currently infected with COVID-19 be vaccinated against influenza?
A: In general, people who are in quarantine following exposure to someone with COVID-19 or in isolation due to infection with COVID-19 should not be brought to a vaccination location to avoid exposing others to COVID-19. For people with moderate or severe COVID-19, vaccination should generally be deferred until they have recovered. For patients with mild or asymptomatic infection with SARS-CoV-2, influenza vaccination may also be deferred to avoid confusing COVID-19 symptoms with potential influenza vaccination-related reactions. Aside from these considerations, there are no other reasons to further defer influenza vaccination following infection with COVID-19. Periodically check CDC guidance on influenza vaccination during the COVID-19 pandemic for updates at www.cdc.gov/vaccines/pandemic-guidance/index.html.
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