Is It Too Late to Get a Flu Shot?


Ideally, older patients receive vaccinations by October, but disease activity often peaks in February or March.

Although each flu season varies in severity, individuals 65 years and older historically bear the greatest burden of the virus, which the COVID-19 pandemic has made more evident. Getting the flu shot annually is the best way for older adults to reduce their risk from flu and possible serious complications. However, patients who have not received flu shots may be wondering whether it is too late.

Ideally, patients receive their flu vaccinations each year by the end of October, but it is important to know that getting vaccinated later than that still provides protection during the peak of the flu season. The CDC monitors the flu virus throughout the year, and the timing of peak infections varies between October and March each flu season.

In 29 of 38 influenza seasons from 1982-1983 to 2019-2020, peak influenza activity occurred in January or later. In 23 of these 38 influenza seasons, the peak was in February or later, and 17 influenza seasons peaked in February.1 Getting the vaccine later in the flu season still provides protection for the remainder of the season. It takes 2 weeks for the immune system to fully respond to a vaccine, so it is important to get the vaccine before an increase in flu activity starts in the community.

Becoming ill with the flu during the season also does not negate the need for a flu shot, as protection is still needed against other circulating influenza viruses. It is also important to know that even after recovering from the virus, older adults may never fully regain their preinfluenza abilities and health, which significantly affects their lifestyles.2

Individuals aged 65 years and older who have underlying conditions, such as diabetes or heart, kidney, or lung disease, are at highest risk for developing life-threatening complications from the flu. This increased risk is in part due to declines in immune response with age.3 The CDC estimates that approximately 90% of seasonal flu-related deaths and between 50% and 70% of seasonal flu-related hospitalizations occur in older adults.4

Older adults who reside in long-term care (LTC) facilities, such as nursing homes, skilled nursing facilities, or other communal spaces, have a higher risk of catching the flu because of the close living quarters, increased fragility of residents, and the movement of staff members and visitors within facilities.5 In the last week of 2022, 786 of 14,188 LTC facilities that reported to the CDC (5.5%) had at least 1 positive influenza result among their residents.6

If 1 laboratory-confirmed influenza positive case is identified along with other cases of acute respiratory illness in a unit of an LTC facility, then an influenza outbreak might be occurring and outbreak control measures may be needed.

For the 2022-2023 flu season, 3 flu vaccines are preferentially recommended by the CDC’s Advisory Committee on Immunization Practices (ACIP) for individuals aged 65 years and older, which include the following:

  • Fluad quadrivalent adjuvanted: This is an inactivated vaccine approved for individuals aged 65 years and older. This vaccine has the same amount of antigen as the standard vaccines but contains an adjuvant, or an added ingredient, which helps create a stronger immune response to vaccination.
  • Flublok Quadrivalent recombinant: This is a recombinant protein vaccine approved for individuals 18 years and older. Recombinant vaccines are created synthetically. This production method does not require an egg-grown vaccine virus and does not use chicken eggs at any stage of the production process.
  • Fluzone High-Dose Quadrivalent: This is an inactivated vaccine approved for individuals aged 65 years and older. This vaccine contains 4 times the antigen of standard-dose inactivated flu vaccines.

These vaccines are known as high-dose or adjuvanted flu vaccines. They can offer greater protection to older individuals who, because of immune system changes that occur with age or chronic health conditions, do not have as strong a response to vaccines as those who are younger. These vaccines have been available for several years; however, they were not previously favored by the ACIP over standard flu vaccines until this past year. If none of these 3 vaccines are available, then any other age-appropriate influenza vaccine is OK to use.

Caretakers and health care personnel who interact with older adults should also get the flu vaccine each flu season. Vaccination reduces their risk of contracting the flu and by staying healthy, they limit the chance of being contagious around others. Caretakers and health care personnel can reduce transmission of the flu virus, staff illness and absenteeism, and influenza-related illness and death if they get annual flu vaccines.

Standard precautions for infection prevention, including avoiding proximity to others, cough etiquette, frequent handwashing, and staying home when sick, should be the norm, alongside routine vaccination. Whether individuals receive the flu vaccine at the beginning or middle of the flu season, they are playing a vital role in protecting themselves and others from serious flu complications.

Developed by the subject matter experts of the American Society of Consultant Pharmacists Antimicrobial Stewardship and Infection Prevention and Control Committee, we are proud to provide the Fall 2022 Senior Immunizations Reference Card to help clinicians and patients provide preventive care.8


1. Grohskopf LA, Blanton LH, Ferdinands JM, et al. Prevention and control of seasonal influenza with vaccines: recommendations of the advisory committee on immunization practices - United States, 2022-23 influenza season. MMWR Recomm Rep. 2022;71(1):1-28. doi:10.15585/mmwr.rr7101a1

2. Schaffner W, Jernigan DB. Preventing flu in older adults. Medscape. November 1, 2017. Accessed January 20, 2023.

3. Cameron K. It’s time to get your flu shot: what you need to know during flu season.National Council on Aging. September 15, 2022. Accessed January 20, 2023.

4. Study shows hospitalization rates and risk of death from seasonal flu increase with age among people 65 years and older. CDC. June 12, 2019. Accessed January 20, 2023.

5. Lansbury LE, Brown CS, Nguyen-Van-Tam JS. Influenza in long-term care facilities. Influenza Other Respir Viruses.2017;11(5):356-366. doi:10.1111/irv.12464

6. Weekly U.S. influenza surveillance report. CDC.UpdatedJanuary 20, 2023.Accessed January 20, 2023.

7. National influenza vaccination week: matte article. CDC. Updated October 28, 2019. Accessed January 20, 2023.

8. ASCP senior immunizations reference card fall 2022. American Society of Consultant Pharmacists. Accessed January 20, 2023.

About the Author

Carmen Witsken, PharmD, is an executive fellow in association leadership and management at the American Society of Consultant Pharmacists in Alexandria, Virginia.

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