Influenza Activity During the 2021-2022 Influenza Season
Since SARS-CoV-2 emerged in the United States in early 2020, influenza activity has been lower than that seen before the pandemic. The adoption of COVID-19–related mitigation measures might have had an impact on the timing or severity of influenza activity. Compared with prepandemic influenza seasons, the 2021–22 influenza season was mild and occurred in two waves, with the second wave having a higher percentage of positive clinical laboratory test results and a higher number of hospitalizations than did the first. Influenza activity peaked later and remained at higher levels than had been reported in previous seasons through late April, May, and early June. During the 2021–22 season, the peak percentage of positive influenza test results from clinical laboratories was the lowest in at least 25 years preceding the COVID-19 pandemic, and the cumulative rate of influenza-associated hospitalizations was lower than in all but the 2011–12 season, the mildest influenza season during the 10 years before the COVID-19 pandemic. The estimate of symptomatic illnesses, medical visits, hospitalizations, and deaths caused by influenza virus infection in the United States during the 2021–22 season is also lower than estimates for any of the 10 influenza seasons preceding the pandemic. The lower level of influenza activity is not because of a decrease in testing for influenza; clinical laboratories reporting to CDC tested ≥1 million more specimens, and public health laboratories tested at least seven times as many specimens, during the 2021–22 season than in any of the five seasons preceding the pandemic.
The first wave of influenza activity during the 2021–22 season peaked in mid-December throughout the country, but the timing of peak activity during the second wave varied by region, ranging from mid-March to May. Notably, the second wave peaked and influenza activity remained elevated nationally later than in any previous seasonal influenza epidemic. The predominant influenza virus throughout both waves was influenza A(H3N2) virus. Most of these viruses belonged to the 3C.2a1b.2a.2 subclade and were antigenically distinct from the reference viruses representing the egg-grown and cell-grown A(H3N2) vaccine components for the 2021–22 Northern Hemisphere influenza vaccines; however, based on preliminary vaccine effectiveness estimates, persons who were vaccinated during the 2021–22 season reduced their risk for influenza illness by approximately one third.
The recommended A(H3N2) component for the 2022–23 influenza vaccine was updated to one that belongs to the 3C.2a1b.2a.2 subclade, the subclade that predominated in the United States during the 2021–22 season. All the influenza viruses collected and tested for antiviral resistance by CDC since October 3, 2022, were susceptible to zanamivir, and the majority (>99%) were susceptible to baloxavir, oseltamivir, and peramivir.
Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022-2023 Influenza Season has been published. CDC recommends annual influenza vaccination for everyone 6 months and older who do not have contraindications.
What’s New for 2022-2023
- New for the 2022-2023 flu season, three flu vaccines are preferentially recommended for people 65 years and older: Fluzone High-Dose Quadrivalent vaccine, Flublok Quadrivalent recombinant flu vaccine and Fluad Quadrivalent adjuvanted flu vaccine. More information is available at Flu & People 65 Years and Older.
- For people younger than 65 years, CDC does not preferentially recommend any licensed, age-appropriate influenza (flu) vaccine over another during the 2022-2023 flu season.
- Additionally, the composition of flu vaccines for the 2022-2023 flu season has been updated to better protect against the flu viruses research indicates will be most common during the upcoming flu season.
- Consistent with prior guidance, everyone 6 months and older should get a flu vaccine, ideally by the end of October. Flu vaccination is especially important for people who are at higher risk of developing serious flu complications, like those with certain chronic health conditions and people 65 years and older.
- More information about the 2022-2023 flu season is available at Frequently Asked Influenza (Flu) Questions: 2022-2023 Season.
For more information on this year’s flu recommendations, see:
- 2022-23 Summary of Flu Vaccine Recommendations
- Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022-2023 Influenza Season Full ACIP Influenza Recommendations
- For detailed guidance about influenza and influenza vaccination for providers, see the CDC’s Flu Website for Healthcare Professionals and CDC’s Health Professionals Quick Resource Links
- For new and noteworthy influenza-related developments and feature stories by influenza season, visit the CDC’s Flu News and Spotlights page.
- See: CDC’s Key Facts about Seasonal Flu Vaccine
- See: Frequently Asked Influenza (Flu) Questions: 2022-2023 Season | CDC
- Also see, Influenza Antiviral Medications: Summary for Clinicians
There are some websites that help providers and patients locate vaccines and Influenza antivirals:
- Flu vaccine locations
Find out where you can get a flu vaccine by asking your primary care provider, going to a local pharmacy, or visiting Find your flu vaccine.
- COVID-19 vaccine locations
Search VaccineFinder for a site near you.
Also see, Influenza Antiviral Medications: Summary for Clinicians
Influenza disease burden
Despite the lower levels of influenza during the pandemic, the overall burden of disease is great. CDC estimates that influenza has resulted in between 9 million and 41 million illnesses, between 140,000 and 710,000 hospitalizations and between 12,000 and 52,000 deaths annually between 2010 and 2020.
CDC now posts preliminary estimates of the influenza disease burden.
Every year influenza vaccines are updated to better match circulating viruses.
Your strong recommendation is important!
A health care provider’s strong recommendation is a critical factor affecting whether your patient gets influenza vaccine. Patients listen to providers when providers strongly recommend vaccination.
- There are many misconceptions about flu vaccine. CDC addresses many of these misconceptions and provides a summary of the benefits of vaccination and selected scientific studies that support these benefits.
- Flu vaccine is recommended for everyone 6 months of age and older who do not have contraindications. While some flu formulations are not recommended for some patients and some patients should not receive flu vaccine at all, this is uncommon. For more guidance on contraindications and precautions for influenza vaccine, please see Table 2 on page 4 in the Summary of Flu Vaccine Recommendations 2022-23 and pages 17-20 in the 2022-2023 ACIP Influenza Recommendations
Below are the links to the latest information and data that might inform your conversations with patients in the upcoming months:
- Flu vaccine offers the best protection against flu-related illness, hospitalization, and death. Flu vaccine reduces this burden of illness. For the latest information about vaccine effectiveness, see CDC’s Influenza Vaccine Effectiveness Studies website.
- Influenza vaccination was found to reduce deaths in children. A study in Pediatrics was the first of its kind to show that influenza vaccination is effective in preventing influenza-associated deaths among children. A 2022 study reported on the vaccine effectiveness against life-threating influenza illness in US children. Clinical Infectious Diseases (CID)
- Influenza vaccination may make illness milder. While some people who get vaccinated may develop influenza, vaccination may make their illness milder. A 2017 study in Clinical Infectious Diseases (CID) showed that influenza vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized influenza patients. A 2021 published study found that in a primarily older population, influenza vaccination was associated with a 41% reduction in risk of hospitalized influenza illness. Journal of Infectious Diseases
- Influenza vaccination has been found effective in preventing influenza-associated hospitalization during pregnancy.
For more information on questions and answers related to this flu season, please see the General information about flu page.
MDPH universally provides influenza vaccine, as well as other routinely recommended vaccines, to all children through 18 years of age. MDPH only provides influenza vaccine for uninsured adults seen at public sites. For more information on state-supplied vaccine, please see the Vaccine Management page.
Nationally, manufacturers have projected they will provide as many as 188-200 million doses of flu vaccine this season. Information about the national vaccine supply can be found at CDC’s Seasonal Influenza Vaccine Supply & Distribution website.
The Immunization Action Coalition (IAC) has a very helpful table of the Influenza Vaccine Products for the 2022-2023 Influenza Season.
When to vaccinate
For most persons who need only one dose of influenza vaccine for the season, vaccination should ideally be offered during September or October. However, vaccination should continue throughout the season, as long as influenza viruses are circulating. The duration of the influenza season varies from, year to year and influenza activity might not occur in certain communities until February or March. In New England, flu activity usually lasts until April and May.
To avoid missed opportunities, providers should continue to offer vaccination during routine health care visits and hospitalizations.
Safe influenza vaccine administration
CDC provides comprehensive vaccine administration resources, including Vaccine Administration eLearn at their Vaccine Administration website
Vaccine information statement
The most recent versions of Vaccine Information Statements (VISs) for Influenza Vaccines (IIV and LAIV4) for use this season are dated 8-06-21. The latest versions of all the VISs can be found at this site.
2022-2023 Influenza Season
Centers for Disease Control and Prevention
- Influenza websites for Healthcare Providers:
- Frequently Asked Influenza (Flu) Questions: 2022-2023 Season
- Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2022-2023 Influenza Season Morbidity and Mortality Weekly Report. August 26, 2022 / 71 (1);1-28.
- Summary: Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP)—United States, 2022-23
- Resources for Mass Vaccination Clinics:
- Planning for Mass Vaccination Clinics:
- Incudes sections on:
- Resources for Hosting a Vaccination Clinic has a checklist of Best Practices for Vaccination Clinics Held at Satellite, Temporary, or Off-site Locations, and other useful material
- Clinic Supplies Check List is a comprehensive list that can be adapted for many settings and is also available in a pdf format
- Antiviral Summary for Clinicians
- Considerations for Planning Curbside/Drive-Through Vaccination Clinics outlines things to take into consideration when planning a curbside or drive-through clinic.
- Planning for Mass Vaccination Clinics:
Immunization Action Coalition
- Model Standing Orders:
- Screening Forms:
- Flu Products Chart:
- VaccineFinder (vaccinefinder.org)is a user-friendly, website where users can search for locations that offer COVID-19 vaccine and seasonal flu vaccine. Just in time for flu season, the Vaccine Finder website has been upgraded and participating providers can now update supply estimates for a more accurate reporting.
American Academy of Pediatrics
American College of Physicians
American Academy of Family Physicians
American College of Obstetricians and Gynecologists
Children’s Hospital of Philadelphia
- MDPH Immunization Division webpage for healthcare and public health professionals
- Flu Information for School Administrators and Childcare Professionals
- Influenza Fact Sheet
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