2021-2022 Flu Season: Influenza Vaccine Choices

The CDC reports that for the 2021-2022 season, manufacturers have projected they will provide as many as 188 to 200 million doses of influenza vaccine for the U.S. market. These nine vaccines will be offered this flu season, starting in late August:

 

As of October 15, 2021, 139.7 million flu vaccines have been administered in the U.S. Flu vaccine supply updates will be provided as they become available at the CDC. Check this page for updates: https://www.cdc.gov/flu/prevent/vaxsupply.htm and check this FDA page for quantities distributed (number of lots) by vaccine product name. It was last updated on October 28, 2021.

According to the Centers for Disease Control (CDC), all flu shots offered this season will be "quadrivalent," meaning they will contain four influenza virus strains.

These viruses were selected to be included in the vaccines dispensed in 2021-2022. Note that seasonal flu vaccines also include protection against the H1N1 virus that is still circulating and was responsible for the "swine flu" influenza pandemic in 2009-2010.

Quadrivalent egg-based vaccines will contain and protect against these flu virus strains:

• an A/Victoria/2570/2019 (H1N1) pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus;
• a B/Washington/02/2019- like virus (B/Victoria lineage);
• a B/Phuket/3073/2013-like virus (B/Yamagata lineage). 

Cell-based (Flucelvax) and recombinant vaccines (Flublok) will protect against:

• an A/Wisconsin/588/2019 (H1N1) pdm09-like virus;
• an A/Cambodia/e0826360/2020 (H3N2)-like virus;
• a B/Washington/02/2019- like virus (B/Victoria lineage);
• a B/Phuket/3073/2013-like virus (B/Yamagata lineage).

Special vaccine options available for seniors age 65 and up

For the 2021-2022 flu season, besides regular flu shot options, two shots are again available for seniors who prefer a vaccine that offers extra protection. The CDC does not recommend one of these vaccines for seniors over the other. A Duke University (along with CDC, Boston Medical Center, and Cincinnati Children's Medical Center) compared the side effects of Fluzone High Dose with Fluad, and preliminary tables of results suggest that Fluad had lower incidence of side effects, but the quality control review of the study has not yet been completed. (Duke study link)

1.      the "high dose" flu shot (Fluzone Quadrivalent High Dose) has four times the amount of antigen than is present in a regular vaccine. Read more about the vaccine on the  Fluzone High Dose CDC information page.
This vaccine has been available since 2009.
Some adverse events (which are also reported after regular flu vaccines) were reported more frequently after vaccination with Fluzone High-Dose than after standard-dose inactivated influenza vaccines.

2.      the "adjuvanted" flu vaccine (Fluad Quadrivalent) has an extra ingredient (an oil-in-water emulsion of squalene oil) called MF59, which helps create a stronger immune response.  Read more about the vaccine on the Fluad CDC information page.
This vaccine was approved in November 2015, and was first available in the U.S. during the 2016-2017 flu season.
Some adverse events (which are also reported after regular flu vaccines) were reported more frequently after vaccination with FLUAD. The most common adverse events experienced during clinical studies were mild to moderate and were temporary, and included pain, redness at the injection site, headache, muscle aches, and malaise.

More highlights about this flu season:

- In October 2021, the FDA expanded the age indication for Flucelvax to include children age 6 months and up.

- FluMist intranasal spray is available for patients age 2 - 49 and is the only option this season if you do not want an intra-muscular shot or the jet injection. The prefilled dosage is .2mL for this vaccine.

- The Jet injector version of Afluria is available for this flu season for those avoiding needles; PharmaJet® Stratis® Needle-Free Injection System is available for age 18 through 64 years.

- Special lower-dose versions for babies: Afluria Pediatric  and Fluzone have half the dosage (.25mL)  as the other brands of shots approved for age 6 months to 36 months, which each contain .5mL of vaccine per dose.  Children aged 6-35 months should receive 0.25 mL vaccine per dose of Afluria Pediatric or Fluzone, but may require more than one dose at least 4 weeks apart.  Flulaval has also been approved for children aged 6 months and up but only comes in the .5mL concentration.  Most of the flu vaccines will be preservative-free in the 2021-2022 season; only those stored in multi-use vials (such as multi-use vials of Fluzone quadrivalent, Afluria quadrivalent, and Flucelvax quadrivalent) contain the preservative thimerosal. Check with your flu shot provider to find out if yours comes in a prefilled syringe (no preservative) or multi-dose vial (will contain a small amount of thimerosal preservative).

- Most people have no or very minor side effects from their flu shot. Some might have the minor effect of a slightly stuffy nose after receiving the live nasally administered vaccine. Other people might have a preference for one type of vaccine (for example an egg-free version) over another. Minor side effects, such as sore arm, might be more severe with high dose or adjuvanted versions compared with a regular flu shot.

Looking Back at the 2020 - 2021 Flu Season

While Covid cases spiked during 2020-2021, flu cases plummeted globally. Normally, the Centers for Disease Control (CDC ) reports millions of cases of flu a year, and tens of thousands of deaths. In the 2020-2021 flu season, (October 3, 2020–May 22, 2021), the CDC reports that influenza activity was lower than during any previous influenza season since at least 1997, the first season for which data are publicly available. Among 1,095,080 clinical specimens tested, just 1,921 (0.2%) specimens were positive for an influenza virus, while in previous years at least 20% of specimens test positive.
This chart shows the number of specimens tested and the percentage of positive tests for influenza viruses, by year — United States, 2016–2021 (See link to full CDC MMWR report below.)

While overall vaccination rates for routine vaccines plummeted during the pandemic, there was an anomaly: flu vaccines. Last flu season, an all-time record was set for the number of flu vaccines administered.

Experts believe that the concern around COVID-19 infection, coupled with increased messaging about the flu vaccine, worked together to boost adherence for last year’s influenza vaccine. A record 192.3 million people were vaccinated for flu during the 2020-2021 flu season. (So far, more than 193 million people, or 70% of adults, have been vaccinated with at least one shot for Covid-19, more than the number who received the flu vaccine last year.) For the entire flu season in 2019-2020, 174.5 million doses were given. For the upcoming flu season, the CDC recommends vaccination by the end of October.
 

Not sure if you have COVID-19 or the flu?
The FDA has approved tests that can differentiate between the two illnesses: https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-covid-19-combination-diagnostic-test-ahead-flu

Use this table to link to ratings and reviews:

- CDC's Frequently Asked Questions about this year's and last year's flu season, including information about the flu viruses and COVID-19 and flu vaccinations: https://www.cdc.gov/flu/season/faq-flu-season-2020-2021.htm

- CDC MMWR report on Changes in Influenza and Other Respiratory Virus Activity During the COVID-19 Pandemic — United States, 2020–2021: Changes in Influenza and Other Respiratory Virus Activity During the COVID-19 Pandemic

- Data on how many people receive flu shot. CDC articles provide weekly vaccination data and projected forecasts for this 2021-2022 flu season.

- How flu vaccines are made: Article from the CDC explains the 70-year old process of making vaccines from chicken eggs. Also explains techniques used for newer cell-based (Flucelvax, approved in 2016) vaccines and recombinant vaccines (Flublok). Cell-based vaccine production could alleviate the possibility of shortages in the event of a flu pandemic, because of quicker production times.

- Information on Recombinant Influenza Vaccine (Flublok) https://www.cdc.gov/flu/prevent/qa_flublok-vaccine.htm. Flublok was initially approved in 2013.

- Vaccines Administered in 2020-2021 season: Changes in Influenza and Other Respiratory Virus Activity During the COVID-19 Pandemic — United States, 2020–2021 

- FDA's Lot Release Status of Vaccines page provides a list of the quantities of different vaccines that the FDA has approved for distribution by manufacturers. Note that FluMist intranasal vaccine has only a small number of lots released so far this season.
https://www.fda.gov/vaccines-blood-biologics/lot-release/influenza-vaccine-2021-2022-season

- More safety information on adjuvanted vaccines: https://www.cdc.gov/vaccinesafety/concerns/adjuvants.html
Although adjuvants make vaccines work better, they can cause more local reactions (such as redness, swelling, and pain at the injection site) and more systemic reactions (such as fever, chills and body aches) than non-adjuvanted vaccines. Also see the Fluad link above.

- Vaccine Adverse Event Reporting System: https://vaers.hhs.gov/reportevent.html
VVAERS is co-managed by the Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA).

- Information on last year's flu season, 2020-2021: https://www.askapatient.com/news/flu-vaccines-for-2020-2021.asp

- Number of people receiving Covid-19 vaccines: https://covid.cdc.gov/covid-data-tracker/#vaccinations

- Related topic: List of Helpful Resources on COVID-19: https://www.askapatient.com/news/patient-guide-coronavirus-websites.asp
Check this resource list for test directories, where to go for travel advisories, statistics, and more.

- Read patient reviews for Fluzone,  Flucelvax (cell-based), Afluria, and Flublok, all quadrivalent vaccines.&  (Note that reviews with dates from 2018, 2019, or 2020 are from those flu seasons.)
Share your experience with your flu shot by using the List of 2021-2022 Influenza Vaccines to link to rating forms.