You may not be able to prevent catching a cold or the flu, but you can greatly reduce your chances and decrease the likelihood that you’ll have a severe case if you do get sick. The well-established advice meant to keep you healthy also protects others by reducing the spread of these diseases.
Get a Flu Shot
“The single best way to reduce the risk of seasonal flu and its potentially serious complications is to get vaccinated each year,” according to the US Centers for Disease Control and Prevention.
Many health professionals, including infectious disease specialist Steven Gordon and infectious disease clinical pharmacist Kaitlyn Rivard, both at the Cleveland Clinic, say the best time to get vaccinated is in September or October, when new annual versions of the vaccines typically become available in North America. But don’t worry if you missed that window, because the second best time is “now.”
Elena Diskin and Lisa Sollot, two respiratory specialists at the Virginia Department of Health, and Christy Gray, the director of the Division of Immunization there, all agree that there’s still time to get the annual flu vaccine. “The season runs from October through the end of April,” they wrote in an email, adding “we typically see the most flu activity in January and February.” So yes, it’s still worthwhile to get a flu shot if you haven’t had one yet.
Flu Vaccines Cannot Give You the Flu
While it’s possible to feel unwell after getting a flu vaccine, you cannot get the flu from it. In public health information about flu vaccines last updated in 2024, the CDC confirms that “flu vaccines cannot cause flu illness. Flu vaccines given with a needle (i.e., flu shots) are made with either inactivated (killed) viruses, or with only a single protein from an influenza virus.” The nasal spray vaccine, which is for people between the ages of 2 and 49, and which you may be able to administer at home, “contains live viruses that are attenuated (weakened) so that they will not cause illness,” according to the CDC.
It takes up to two weeks for the vaccine to have its full effect, however. That means if you were exposed to the flu virus either right before or up to two weeks after receiving the vaccine, you could get sick, but it wouldn’t be due to the vaccine.
Flu Vaccines Are Highly Effective at Preventing Severe Illness
The flu vaccine changes every year based on which strains of the virus experts think will be prevalent, and while it’s not foolproof, it is highly effective at preventing severe illness. In the 2024-2025 season, for example, flu vaccines were 56 percent effective, which is higher than it had been in almost 15 years.
“Vaccine effectiveness is measured by comparing the frequency of health outcomes (e.g., symptomatic illness, hospitalization, death) in vaccinated and unvaccinated people in the real world,” say Diskin, Solot, and Gray at the Virginia Department of Health. Effectiveness is different from efficacy, which measures outcomes in controlled trials.
“In plain language, [vaccine effectiveness] describes how much less likely a vaccinated person is to get sick compared to an unvaccinated person, based on real-world data,” says Sai Paritala, an assistant professor at the University of Nebraska Medical Center College of Public Health and a former epidemiologist.
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