Why are there special flu shots for older adults?

Infectious Diseases Vaccines

People who are at least 65 years old can get a flu shot specially developed for their age group, and it offers better protection from the flu.

Influenza vaccines have been around for nearly 80 years, and have undergone a number of changes during that long history. One of the more recent changes is the emergence of flu vaccines specially designed for older adults.

These targeted vaccines were developed to solve a problem: flu vaccines substantially reduce flu risks for older adults, but those benefits aren’t as large as we see in younger population groups.  Older adults still account for a big share of all flu-related hospitalizations and deaths.

Beginning in our 50’s or 60’s, our immune systems become considerably less responsive, a process known as immunosenescence. (You can take that word to the bank!) Because of this loss of responsiveness, older adults’ immune response to many vaccines–including the standard flu vaccine–is not as strong as we would like.

This year, the CDC recommends three options for older adults that improve flu outcomes compared to the standard flu vaccines.

But before we continue, an important note: If none of these options is available, it’s better to get a regular annual flu vaccine than nothing. Some protection is still better than no protection.

💉Fluzone High-Dose flu vaccine for people aged 65 and up

The Fluzone high-dose flu vaccine was the first flu vaccine licensed by the FDA and specially developed for older adults. It was licensed in 2009 and first used in the 2010-2011 flu season. Fluzone contains substantially more active ingredients (antigen components) than the standard flu vaccine. We can think of it as a louder signal. This bigger dose produces a stronger antibody response in older adults, and that translates into better protection against the flu. A large randomized study showed that Fluzone High-Dose was about 25% more effective at preventing flu, compared to the standard-dose flu vaccine, for people who are at least 65.

The high-dose vaccine has a similar safety profile compared to the standard-dose vaccine. Overall, flu vaccinations are extremely safe.

Since 2009, two other approaches have emerged.

💉💉Flublok: recombinant flu vaccine for people aged 18 and up

A recombinant flu vaccine is available for people aged 18 and up and is one of the three preferred vaccines for those over age 65. This vaccine is called Flublock, and it was licensed in 2013.

Without getting into the weeds, the recombinant vaccine works like this: the important bits of the flu virus genetic code are incorporated into a virus that infects insects. An insect cell culture is then infected with the modified insect virus. It makes a lot of flu proteins, which are separated out and made into the vaccine.

All of the technical details aside, Flublok contains a higher dose of flu antigen than the standard flu vaccine. Flublok does a better job of reducing the risk of infection and serious outcomes in the general population and specifically in older people compared to a standard seasonal flu vaccine. Its safety profile is the same as the standard-dose vaccine. However, some reports suggest that this one is harder to find.

💉💉💉 Fluad: adjuvanted flu vaccine for older adults. 

Fluad Quadravalent is an adjuvanted flu vaccine for adults who are at least 65. It was approved by the FDA in 2015.

An adjuvant is a “helper”–something added to a vaccine to help it work better. The adjuvant in the flu vaccine for older adults is MF59, a mix of squalene (a naturally occurring oil) and water. Squalene is also commonly added to moisturizers and lip gloss, and can be found in eggs and wheat germ. From what this author can figure out, the squalene in vaccines is probably a highly processed product of shark livers.

Anyways, adjuvanted flu vaccines produce higher antibodies in recipients. There is also evidence that they are more effective at preventing flu-related hospitalizations and deaths in older adults, and they’re just as safe as standard flu vaccines.


In terms of side effects, one study tested the standard-dose vaccine head-to-head with all three of these enhanced vaccines in a population of older adults. Arm soreness was a little more frequent for Fluzone high-dose and Fluad adjuvanted vaccines. Otherwise, there were few differences.


Older adults may get better protection from flu by seeking out a flu vaccine specially developed for their age group. CDC recommends that people who are at least 65 choose Fluad, Flublok, or Fluzone High-Dose, if they can. These options are all just as safe, and are more effective than a standard-dose flu vaccine.  If one of those isn’t available, just go for a standard flu vaccine, which will offer much better protection than nothing at all.

Stay safe, stay well.

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