When to get the flu shot? Best timing for the flu vaccine?

Influenza (flu) is a serious disease that can lead to intense sickness, hospitalization, and even death. Flu is an easily spread virus that leads to thousands of hospitalizations and deaths each year. The flu often comes on suddenly and includes symptoms such as:

Fever and/or chills
Headaches
Muscle or body aches
Sore throat
Fatigue
Cough
Runny nose
Congestion/stuffiness
Vomiting and/or diarrhea (most common in children)

Flu viruses are transmitted when those infected cough, sneeze, or speak and spread viral droplets. Influenza can also be spread by touching your eyes, nose, or mouth after encountering a surface or object that has been contaminated with flu virus(es).

For added protection against influenza, healthcare professionals recommend getting a flu shot before flu season begins. In the United States and Northern Hemisphere, flu season most commonly means autumn and winter, but flu seasons are different and the virus that causes influenza changes over time and season. So when is the best, most effective time to get a flu shot? MyFluVaccine is here to help you decide when to get your seasonal flu shot and answer any questions related to influenza vaccinations.

How Do Flu Vaccines Work?

Like other vaccines, the flu shot builds antibodies, which—in the case of the influenza vaccine—often show up about two weeks after immunization. The antibodies work to protect the body from flu illness. Because the flu is often considered a seasonal disease, in the late winter and early spring, international (the World Health Organization, or WHO) and federal (the Federal Drug Administration, or FDA) health experts follow the most prevalent strains of influenza and adapt a seasonal flu vaccine to combat the strains that research predicts will be most common for an impending season. According to the Centers for Disease Control and Prevention (CDC), "All flu vaccines in the United States are 'quadrivalent' vaccines, which means they protect against four different flu viruses: an influenza A(H1N1) virus, an influenza A(H3N2) virus, and two influenza B viruses" (Key Facts About Seasonal Flu Vaccine | CDC)². This approach is intended to provide the most protection based on data and spread, and experts continue to track how virus strains might change and circulate.

If the chosen viruses in the flu vaccine products match the strains that end up spreading during flu season, then more people will be safeguarded against influenza, and while sometimes the vaccine and virus combination may not be a match, research shows that the flu vaccine will still protect against severe flu symptoms.

It is also very likely that influenza and COVID-19 will simultaneously circulate during flu season. This can exacerbate symptoms and the propensity for hospitalizations, especially among vulnerable groups like those who are pregnant, children, the elderly, and those who are immunocompromised or live with a chronic illness. The flu vaccine does not prevent COVID-19—and vice versa—but getting a flu shot early can prevent flu, minimize its spread, and soften symptoms. You can also reduce the spread of the flu, COVID-19, and their effects by washing your hands, covering your mouth when sneezing or coughing, and staying home when sick.

Even if—prior to getting vaccinated—you get sick with influenza, vaccination is still recommended to combat other potential flu strains. Plus, when more people are vaccinated, it lessens the likelihood of communal spread and conserves health care resources for patients with other serious illnesses, including COVID-19.

When Should You Get Your Flu Vaccination?

The CDC suggests that you get a flu shot by the end of October. Flu vaccines work best when given before flu season is in full swing because it takes about two weeks for the shot to deliver antibodies needed to fight influenza. The earlier in the season, the better. However, if you wait until after October, a flu shot is still recommended because it can help protect you throughout the remainder of flu season.

It is also important to note that flu vaccines for children (over 6 months) consist of two doses, which may require more planning or an earlier first dose so that children are prepared at the start of flu season. For people 65 and over, an early vaccine (before autumn) is not recommended, as vaccine effectiveness can dwindle over time, and heightened protection is important for this group. However, pregnant people who reach their third trimester in the late summer months may consider getting the flu vaccine early—in July or August—to protect infants born during flu season (since their newborns will be too young to get vaccinated).

Types of Influenza Vaccines

All influenza vaccines in the US are quadrivalent, meaning they have been established to protect against four different flu viruses (typically two Influenza A viruses, and two Influenza B viruses). To find out more about the specific influenza strain combinations for the 2022-2023 flu season, see Influenza Vaccine for the 2022-2023 Season | FDA².

For those younger than 65, the CDC does not recommend a particular flu vaccine over another, but for those 65 years and older, three types of flu vaccines are advised: Fluad^® Quadrivalent, Flublok^® Quadrivalent Recombinant, or Fluzone^® High-Dose Quadrivalent. Getting these types of vaccines have been found to offer more protection and be more effective for people over 65 years. However, if for some reason the above recommended vaccines for those 65+ are not available in your area, getting any age-appropriate flu vaccine is advised.

There are several private manufacturers for flu vaccines. Some of these manufacturers include: AstraZeneca, GlaxoSmithKline, Sanofi, and Seqirus. It is projected that the US will be supplied with 173.5 – 183.5 million doses of influenza vaccines, yet based on flu progression and activity of the season, these vaccination numbers are subject to change.

Types of Flu Vaccines Include:

Standard-dose flu shot (virus is grown in eggs)*: Approved for use in children 6 months+ and anyone 18+. These types of flu shots are administered in the arm muscle by needle. Afluria^® Quadrivalent, Fluarix Quadrivalent, Flulaval^® Quadrivalent, and Fluzone^® Quadrivalent.
Cell-based flu shot: A completely egg-free vaccine, this type is grown via cell culture and is approved for those 6 months and older. Flucelvax^® Quadrivalent.
Recombinant flu shot: Another egg-free option, this flu shot is approved for people 18 years+. This type of flu shot is made with three times the antigen than other flu vaccine options, which aids your body in creating a deeper immune response. An antigen is part of a vaccine that builds antibodies, thus creating greater protection in the body. Flublok^® Quadrivalent Recombinant.
Adjuvanted flu shot (egg-based)*: This vaccine is for use in people who are 65+, and contains an adjuvant (a substance used to enhance the body's immune response to an antigen). Fluad^® Quadrivalent.
High-dose flu shot (egg-based)*: Designed and approved for those 65+, this has four times the antigen amount than standard-dose flu vaccines. Fluzone^® High-Dose Quadrivalent.
Live attenuated nasal spray flu vaccine (egg-based)*: This flu vaccine spray is created with weakened live flu viruses and is administered through the nose. While it is approved for people ages 2 – 49, it is not recommended for use in pregnant people, those who are immunocompromised, or those with some medical conditions. FluMist^® Quadrivalent *For a list of certain conditions, see the CDC's shared information, The Nasal Spray Flu Vaccine (CDC)³.

Make plans to get your flu shot by checking with your healthcare provider to know which vaccine is right for your age and medical condition(s).

*It is recommended that individuals who are severely allergic to eggs be vaccinated for the flu in a healthcare setting with medical professionals who can notice and treat severe allergic reactions. However, based on numerous studies, it is unlikely that severe allergic reactions will occur with the use of egg-based flu vaccines. As noted above, there are two completely egg-free flu vaccine options: Flublok^® Quadrivalent Recombinant and Flucelvax^® Quadrivalent.

Where Do I Get a Flu Shot?

Flu vaccines are often given at healthcare offices and clinics, but you don't need a primary care physician to protect you from the flu. The flu vaccine can be easily accessed at many pharmacies, urgent care clinics, and college health centers prior to flu season. Some workplaces or organizations even offer vaccinations [often free] on-site or will provide a voucher for their members to get a flu shot locally. If you're not sure where to start, check with your community's Public Health office, your insurance carrier, and/or your local pharmacy.

See the "Health Facilities and Clinics Near You" section below.

Expert Opinions & Safety Measures

Health and epidemiology experts not only research, track, and predict early influenza strains, but they also ensure that flu vaccines remain safe, effective, and that vaccine manufacturers follow strict guidelines to meet high quality standards. The FDA and CDC work together (along with other agencies like the Centers for Medicare and Medicaid Services and the Veterans Health Administration) to provide supervision of flu vaccines and medical products that are distributed to the public.

The Vaccine Safety Datalink (VSD)—part of the CDC's Immunization Safety Office in collaboration with nine healthcare organizations across the US—also continues to monitor the safety of vaccines through sustained research and health data before and after vaccines are administered. In addition, the FDA maintains the Biologics Effectiveness and Safety (BEST) Initiative, which examines vaccine safety in real-world and clinical conditions. The FDA and CDC assess reports of adverse events following all types of vaccinations (including for influenza). These reports are typically generated by healthcare professionals, vaccine recipients, and vaccine manufacturers to the Vaccine Adverse Event Reporting System (VAERS).

Health Facilities & Clinics Near You

Follow the link below to find a flu vaccine location by zip code and vaccine type:
Search for Flu Vaccine Locations (Vaccines.gov)⁴.

After Getting Your Flu Vaccine

The flu vaccine can cause some mild side effects, which may include:

Soreness, redness, and/or swelling at the injection site
Fever
Headache (low-grade)
Nausea
Fatigue
Muscle Aches

If you have received a flu vaccine and begin experiencing flu symptoms (other than the mild vaccine side effects), this may mean you were exposed to flu viruses before vaccination or within the two-week period after receiving your vaccine, and before your body was able to build up immune protection. Flu symptoms are also similar to other respiratory illnesses, such as COVID-19.

Even if you are vaccinated, you can still be infected with the flu virus, for not all flu viruses are represented in the flu vaccine. The good news is that the flu vaccine you received—even if you've been exposed to an influenza virus that was not part of the vaccine—may still reduce the severity of your particular flu symptoms and protect you from hospitalization and death. With these notions in mind, the CDC maintains their recommendation for everyone 6 months and older to be vaccinated against the flu.

Conclusion

Overall, flu vaccines are rigorously tested and monitored for safety and effectiveness. Depending on the strains chosen each flu season and how well they match what circulates, a flu shot could defend you from severe symptoms at the very least. Getting a flu shot before the season begins (usually in autumn) is your best bet for protecting yourself and your community this flu season. Ask your doctor or healthcare professional which flu vaccine is best for you.

When to get the flu shot: What is the best timing to take the flu vaccine to prevent influenza?