How Effective Are Flu Shots?

March 20, 2023

Getting a yearly flu vaccine is a good way to lower your risk of illness, hospitalization, and death—and it keeps those around you safe too.

Are flu (influenza) vaccinations really effective?

In some years, effectiveness is as high as 40% to 60%. Some types of influenza viruses are more susceptible to vaccinations than others, so a lot depends on which virus is most prominent in any given flu season. Virologists at the Centers for Disease Control and Prevention (CDC) study which virus type is likely to be most prevalent in any given year and decide which vaccine is to be given. If the chosen vaccine happens to be a good match that season, then the incidence of infection will be low, and infections that do occur will be mild.

The influenza vaccine given during the 2018 to 2019 influenza season is estimated to have prevented 29 million flu illnesses, 13 million flu-related medical visits, 380,000 flu-related hospitalizations, and 28,000 flu deaths. Some studies have shown that among patients admitted to the hospital with influenza, immunized individuals were less likely to be admitted to intensive care units (ICUs).

The flu shot for differnet populations

  • Among patients with heart disease, vaccination lowers the risk of heart attacks during flu season.
  • Patients with chronic lung disease lower their risk of worsening lung disease by getting vaccinated, and diabetic patients lower the risk of hospitalization and worsening of their diabetes.
  • One study showed that pregnant women reduced their chance of being hospitalized with flu by half with vaccination, and their babies were protected against the disease for their first few months after birth, before they were eligible for vaccination.
  • For older people, vaccination not only lowers the chance of complications inherent from hospitalization but also the risk of death.

The bottom line

For all available age groups, the CDC recommends annual influenza vaccination. A good time to get vaccinated is around September or October each year. But even if the new year has already passed, the influenza vaccine is still effective as we often see a plenty of influenza cases up until March.

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