Updated

Some experts are warning older adults against getting their flu shot too early because it’s unclear how long the vaccine lasts.

NPR reported that despite flu season being weeks or months away, many companies such as CVS are offering coupons for customers who get the flu shot. The vaccine typically becomes available in August and is advertised until the springtime or for as long as supplies last. For many stores, the flu shot is a way to draw more customers in to buy other items in store, the news website reported.

While federal health officials argue getting the flu shot later or too soon is better than not getting vaccinated at all, some experts argue stores’ marketing schemes may be clouding the science.

"If you're over 65, don't get the flu vaccine in September. Or August. It's a marketing scheme," Laura Haynes, an immunologist at the University of Connecticut Center on Aging, told NPR. These individuals’ immune systems may cause the vaccine to wear off faster than in young people.

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The Centers for Disease Control and Prevention (CDC) recommends that vendors make the flu shot available as soon as possible but points out that delaying vaccination may offer greater protection later in the season. The CDC advises against deferral from vaccination, however, because “it could result in missed opportunities to vaccinate,” NPR reported.

But Dr. John J. Treanor, an infectious disease specialist at the University of Rochester School of Medicine & Dentistry, told the news website that some studies suggest the strength of the flu vaccine may wane as the season progresses. The strain of the flu virus and how well scientists match the vaccine to that strain in any given year can also impact immunity. However, data shows it’s important to vaccinate children and the elderly, as these groups are most at risk of flu complications and death.

Haynes advised older patients to consult their doctors for vaccination timing but said between Halloween and Thanksgiving are ideal for this age group.

“If you can't wait, and the only chance is to get it in September, then go ahead and get it. It's best to get it early rather than not at all,” she told NPR.