As flu season approaches, getting a flu shot and timing it right will help protect you and your loved ones from a potentially serious illness.

Each year, about 8% of the U.S. population contracts the flu. While most cases are moderate, the flu can lead to hospitalization and even death.

“Each flu season is different, but in a typical flu season, millions get the flu, hundreds of thousands of people are hospitalized, and thousands to tens of thousands die from flu-related causes,” says pharmacist Matthew Burdett, PharmD. “Getting vaccinated is the best means of protection.”

Why an annual shot?

The flu vaccine is designed to protect against the strains of influenza virus that are most likely to circulate in a season. Yearly vaccination is needed for the best protection.

“The influenza viruses are constantly changing and mutating, so each year the flu vaccine is updated to include four strains that are most likely to be circulating that year,” Dr. Burdett explains. “Also, a person’s immune protection declines over time, so annual vaccination is needed for optimal protection.”

Who is most impacted by the flu?

While it is recommended that everyone aged 6 months and older get an annual flu vaccine, certain populations are at a higher risk of developing severe complications. These individuals should prioritize getting vaccinated to protect themselves and minimize the impact of the flu on their health.

1. Adults aged 65 and older: Older adults have a higher risk of flu-related complications due to age-related changes in their immune system.

2. Individuals with certain health conditions: People with chronic illnesses such as asthma, heart disease, diabetes and kidney disease are more susceptible to severe complications from the flu.

3. Pregnant women: While pregnant, women experience changes in their immune system that make them more vulnerable to respiratory infections like the flu.

4. Young children: Children under the age of 5, especially those under 2 years old, are at a higher risk of developing complications from the flu.

5. Those with immunocompromising conditions: Individuals with compromised immune systems, such as those undergoing cancer treatment or with HIV/AIDS, have a weaker ability to fight off infections like the flu.

Ideal timing for a flu shot

Timing plays a crucial role in the effectiveness of the flu shot. While the influenza viruses spread year-round, they historically peak between December and March, with February being the most common month for peak activity.

“Because it takes up to two weeks to build immunity from the vaccine, it’s usually best to get flu vaccines in September and October,” Dr. Burdett says. “If you missed that window, you can still protect yourself against flu outbreaks, particularly in years with a later peak.”

Other considerations

For those over age 65, a high-dose flu vaccine can produce a stronger immune response. Data shows that standard-dose flu shot does not work as well in adults over age 65.

Additionally, Dr. Burdett says some data suggests using a high-dose flu shot in immunocompromised patients, even when they are younger than 65 years old, elicits stronger immune responses.

“There can sometimes be insurance issues because it’s outside the normal indications, and not all pharmacies can administer a high-dose shot to those under 65,” he says. “So, it would be best to get in a clinic or have a prescription with a note on the prescription sent to the pharmacy.”