- The CDC "preferentially recommends" adults ages 65 and older receive higher-dose or adjuvanted flu shots this year.
- The three recommended flu shots are the Fluzone High-Dose Quadrivalent, Flublok Quadrivalent, and Fluad Quadrivalent flu vaccines.
- If none of the recommended vaccines are available at the time of vaccination, seniors are still recommended to receive a standard-dose unadjuvanted flu shot.
For the first time, federal health officials are "preferentially" recommending seniors receive higher-dose or adjuvanted flu vaccines this year, during the 2022-2023 flu season.
People ages 65 or older often bear the greatest burden of severe disease from the flu, with the majority of flu-related hospitalizations and deaths occurring in that population, the Centers for Disease Control and Prevention (CDC) said in a June media statement. Older adults may also not have as strong of an immune response to vaccines as younger people.
"Given their increased risk of flu-associated severe illness, hospitalization, and death, it’s important to use these potentially more effective vaccines in people 65 years and older,” José R. Romero, MD, Director of CDC’s National Center for Immunization and Respiratory Diseases, said in the statement.
The recommendations may also help to close racial and ethic gaps in those who receive high-dose flu vaccines by making the shots more available and accessible to minority groups, Dr. Romero added.
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Three Recommended Vaccines for Seniors
Based on recommendations from the CDC’s Advisory Committee on Immunization Practices (ACIP), the CDC moved to “preferentially recommend” one of three vaccines for people ages 65 or older this year.
- Fluzone High-Dose Quadrivalent (HD-IIV4): An inactivated flu vaccine that contains four times the antigen as standard dose flu vaccines. The higher dose of antigen—or the part of the vaccine that helps the body build protection against the virus—is intended to give older adults a better immune response, and thus, better protection.
- Fluad Quadrivalent (aIIV4): A standard-dose, inactivated flu vaccine that contains an adjuvant, or an ingredient added to the vaccine to help elicit a stronger immune response. In this case, the adjuvant is called MF59, and is an oil-in-water emulsion of squalene oil.
- Flublok Quadrivalent (RIV4): A recombinant flu vaccine made using a newer technology that does not use the actual flu virus or chicken eggs in the manufacturing process. Recombinant vaccines are created synthetically. The recombinant vaccine also contains a higher antigen dose.
The CDC doesn't recommend any of those preferred vaccines over the others. Instead, it urges seniors to get any of those three vaccines available to them, instead of a standard-dose unadjuvanted flu vaccine.
Evidence comparing the efficacy of high-dose flu vaccines and adjuvanted flu vaccines against confirmed cases of the flu, and across multiple flu seasons, is also lacking.
“Looking at the data from all the studies thus far, there is no consistent relative benefit note for one of the three influenza vaccines over another across multiple seasons,” Mary Ann Kliethermes, PharmD, director of medication safety and quality for the American Society of Health-System Pharmacists Inc., told Health. “That is why any of the three are currently recommend by the CDC. In my perspective, with what the research evidence shows, it does not matter which agent is used.”
Ultimately, after reviewing all of the available data, the CDC panel "noted there is not enough evidence to confidently choose one of the vaccines is better than the other,” said Kliethermes.
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Reasoning Behind the New Recommendations
Older people have an increased risk of developing serious and potentially life-threatening complications from a case of the flu, compared to younger adults.
According to CDC data, up to 85% of flu-related deaths, and up to 70% of flu-related hospitalizations occur in people 65 years and older.
This is, in part, due to our immune systems becoming weaker as we age—and as the immune system weakens, we not only become more susceptible to illness, but vaccines meant to bolster our immune system also aren't as effective.
According to the CDC media statement, the recommendation for these three vaccines for the over-65 population was based on a review of available studies which suggests that the high-dose or adjuvanted vaccines are "potentially more effective" in that group than the other standard-dose unadjuvanted vaccines.
A trivalent version of the Fluzone High-Dose vaccine, specifically, was shown to be 24% more effective in preventing the flu in older adults, as compared to the standard-dose vaccine, according to a 2014 study published in the New England Journal of Medicine.
Observational data shared by the CDC also shows that the trivalent Fluad adjuvanted vaccine provided greater protection against flu-related hospitalizations and emergency department visits among Medicare beneficiaries than unadjuvanted standard-dose vaccines. That vaccine was also beneficial among nursing home residents, lowering their risk of hospitalization and pneumonia, data suggests.
That said, there are currently no available studies comparing the quadrivalent high-dose vaccine and adjuvanted vaccine with the standard-dose vaccine.
Despite their potentially higher effectiveness, the higher-dose and adjuvanted vaccines may lead to more frequent side effects—both at the injection site and systemically—than the unadjuvanted standard-dose vaccines.
"It is interesting to note in these studies patients have more side effects, injection site reactions, with the more potent vaccines," said Kliethermes.
The most common side effects for both the high-dose and adjuvanted vaccines observed during studies included pain, redness at the injection site, headache, muscle aches, and malaise. The side effects, however, were mild and temporary.
Preferentially recommending these flu shots for older Americans will hopefully increase accessibility and promote greater vaccine uptake in that population for the upcoming flu season.
According to Kathleen Cameron, BSPharm, MPH, senior director of the Center for Healthy Aging at the National Council on Aging (NCOA), clinicians and vaccine providers are urged to follow the new vaccine guidelines for people over 65. However, if none of the higher-dose or adjuvanted vaccines are available at the time of vaccination, a unadjuvanted standard-dose vaccine will do.
“[The] NCOA is hopeful that these new CDC recommendations for flu vaccines for older adults will move clinicians and vaccine providers to stock and administer these recommended vaccines so that they will be more available in a more equitable manner than they have been in the past,” Cameron told Health, adding that she hopes the vaccines will be more accessible to underserved communities as well.
Overall, the goal this year "is for all older adults to receive one of the recommended more effective flu vaccines," said Cameron.