Why It's Not Too Late for a Flu Shot

If you haven't gotten around to getting a flu shot yet, it's not too late to get vaccinated. Cases of the flu usually peak in February and sometimes continue into May.

The Centers for Disease Control and Prevention (CDC) says cases of the flu were up last week from the week before. Every year, up to 200,000 Americans are hospitalized for flu-related complications, and as many as 49,000 die.

Center for Disease Control and Prevention

Why your age matters

Getting vaccinated is especially important for people 50 and up, who are more likely to have other medical conditions—such as diabetes, heart disease, and obesity—that can worsen flu complications.

If you’re 65 or older, your risk of flu-related complications, hospitalization, or death is even higher, says Andrew Pekosz, Ph.D., a professor in the molecular microbiology/immunology and environmental health sciences departments at Johns Hopkins University Bloomberg School of Public Health. “And if you do get the flu, a vaccination can lessen the disease’s severity.”

Which vaccine to get

The predominant strain so far this season is the influenza A virus H3N2. This virus is especially hard on older adults, and H3N2 seasons are typically tough ones, notes the CDC.

Adults 50 and up should consider the quadrivalent vaccine, which contains four different inactivated strains of the flu. The standard shot, called the trivalent, protects against three of the most common flu strains.

Adults 65 and up can opt for the Fluzone High-Dose or the new FLUAD shot. Both are trivalent vaccines specially designed for seniors. Fluzone High-Dose contains four times the standard shot’s flu-antigen dose, which is meant to induce a stronger immune response for better protection against the flu. (The CDC cautions, however, that both the Fluzone High-Dose and FLUAD vaccines may cause more side effects than a standard-dose shot. These may include pain, redness or swelling at the injection side, headache, muscle aches, and discomfort.)

What else to know

Keep in mind that a flu shot is not fully effective until two to three weeks after vaccination. “If people are going to get the vaccine, they should do it today," says William Schaffner, M.D., a professor in the division of infectious diseases at Vanderbilt University School of Medicine in Nashville.

If you’ve already had your flu vaccine, a second shot will do you no good. "Studies have shown that a booster flu shot in the same season doesn’t really improve your immune response,” Pekosz says. But if you’re 65 or older, consider also getting a pneumococcal vaccine, which can decrease your risk of common flu-related complications such as pneumonia, meningitis, and bloodstream infections.

If you get sick

What should you do if, despite getting your flu shot, you come down with flu symptoms? Many people don’t seek timely treatment once they feel the virus coming on. Antiviral drugs reduce the virus’s ability to reproduce, which lessens symptoms and shortens the amount of time you’re sick; you take the drugs for about five days.

Because antivirals are more effective when started early, doctors should prescribe them for high-risk individuals before results of diagnostic testing are available. If you’re at low risk and are 65 or younger, you may not be a candidate for an antiviral after the 48-hour window; after two days it’s unlikely the drug will be of benefit to you.

First published Feb. 7, 2017; this version is updated.