By mid-September, the signs advertising flu shots were already in your local drugstore and your doctor’s office.

Some doctors recommend waiting…or even getting a second shot later in the season. Why? There’s a concern that vaccine protection may not last the entire flu season if you get the shot too early. That’s an issue especially for older people and those with compromised immunity.

But delaying your vaccination may backfire, says William Schaffner, MD, professor of preventive medicine and infectious disease at Vanderbilt University School of Medicine in Nashville. After all, if the season starts early—like it did in 2009, reaching peak levels in October rather than the more typical December through February—you could get sick while waiting for the “optimum” time to get protected. And while the idea of getting an early shot followed by a booster shot later in the flu season sounds logical, there are no broad studies on whether it actually works, and some narrow studies (on very ill people) have had conflicting results. It’s possible that a few months after a flu shot, the body is just not ready to respond to an additional shot—or a new strain of flu not covered by either shot may have appeared.

Dr. Schaffner has better suggestions for protecting yourself.


The tendency for flu protection to be less effective over time is called waning immunity, and it’s a particular concern for older people, who don’t mount as robust an antibody response to the vaccine as do younger people in the first place. Plus, antibody levels drop more quickly in older people than in younger ones.

A review of eight studies in adults over age 60 showed that after vaccination, protection was maintained for as little as four months for some flu strains, although for other flu strains there was protection for six months or longer. It’s not entirely clear if the waning immunity is due to fewer antibodies in your system…which we know happens…or simply because new flu strains may pop up later in the season. But it’s a real concern.

The same phenomenon—fewer antibodies, quicker drop in antibody levels—occurs in anyone with a weakened immune system due to a medical condition or certain medications.

The irony is that protection against flu is particularly important as we age, especially for people with chronic conditions such as heart disease or diabetes. The flu vaccine, imperfect as it is, reduces the risk for hospitalization in people over age 50 by 60% and for those with diabetes by about 80%.


According to Dr. Schaffner, people age 65 and older, or anyone with a chronic condition that affects immunity, have two good options…

• Ask your doctor for the high-dose vaccine. It was specifically created for people age 65 or older and for those with weakened immunity. It has four times the amount of antigen, the substance that prompts our bodies to develop antibodies, as regular flu shots. More antigen leads to more antibodies, and the high-dose vaccine has been shown to boost protection by an additional 24% compared with a standard flu shot, saving many seniors from becoming sick. It protects against three influenza strains.

• If you’re under age 65, you may want to ask your doctor about the quadrivalent vaccine. It protects against a fourth strain of flu virus. Flu strains are classified as “A” or “B”—the high-dose vaccine mentioned above protects against two As and one B, while the quadrivalent protects against two As and two Bs. “The B strains usually become more prominent later on in a season, so a quadrivalent vaccine may bolster your protection for the tail end of flu season,” said Dr. Schaffner. These days, most regular (non-high-dose) flu vaccines are quadrivalent, but be sure to ask your doctor or pharmacist to make sure that you’re getting one.

• Even if you’re 65 or older, the quadrivalent vaccine may still be the right choice for you. If you’re generally healthy, you may not need the extra antigen in the high-dose vaccine, but you could benefit from the protection against more B flu strains in the quadrivalent one. That’s a good conversation to have with your doctor.

Once you decide which vaccine is best for you, Dr. Schaffner recommends getting it on the early side—in September if possible. Why? For one, it takes up to two weeks for your body to mount its full antibody response and be as protected as possible. Plus, you’ll have gotten your shot—no possibility of forgetting, postponing, procrastinating…and then getting sick. Says Dr. Schaffner, “A vaccine delayed is often a vaccine not given at all.”