Yearly Flu Vaccines Give Kids Special Immune Boost

The percentage of Americans who get an annual influenza vaccine has stayed at around 50% for years. While most people can get a flu shot—from the youngest to the oldest—new research is showing that kids may get a special boost from it.

According to a new study, getting a flu vaccine every year provides young children with antibodies that offer broad protection against new strains—a benefit that older kids and adults don’t get.

The study, which was published in the journal Cell Reports Medicine, analyzed data on immune responses of children between the ages of 3 and 15 years.

The researchers found that children were more likely to produce broadly protective antibodies against the flu when they were younger.

As they grew up, the antibodies they produced from either being infected with the flu or being vaccinated against the virus were still effective against influenza, just less broad.

The researchers also compared antibody responses from the flu shot compared to the nasal spray vaccine and found that both were equally effective at producing protective antibodies.

How the Flu Vaccine Works

The flu vaccine makes your body form antibodies against certain strains of the influenza virus. It takes about two weeks after you’re vaccinated for that protection to take effect.

The antibodies help protect you from getting infected or seriously ill with the strains of the flu that are circulating in a particular season.

Each year, researchers analyze data from around the world to try to figure out which strains of the flu virus will be the most common for the upcoming flu season. Then, they try to tailor the vaccine to match.

All flu vaccines in the United States protect against either three (trivalent) or four (quadrivalent) strains of the flu: an influenza A (H1N1) virus, an influenza A (H3N2) virus, and one or two influenza B viruses. (Only quadrivalent vaccines are available for the 2021–2022 flu season.)

How Well Do Flu Shots Work?

The flu vaccine is different each year, which means its effectiveness can vary from flu season to season.

Centers for Disease Control and Prevention (CDC) data show that the shot’s efficacy at preventing a flu infection has ranged from as low as 10% during the 2004–2005 flu season to as high as 60% during the 2010–2011 flu season.

Effectiveness from the 2019-2020 season—the most recent season that data is available for—shows that the vaccine was 39% effective at preventing the flu in people who received it.

The Importance of Flu Shots

Thomas Russo, MD, a professor and the Chief of Infectious Disease at the University at Buffalo, told Verywell Health that while the flu vaccine “isn’t perfect, it does help protect people from landing in the hospital.”

According to Russo, the latest study shows that your response to the flu vaccine is “in part dictated by your prior exposure to live flu strains, prior vaccination, and the timing of that.”

Russo added that children may have more of a broad antibody reaction to the flu vaccine simply because they haven’t been exposed to the flu often—if at all.

Richard Watkins, MD, an infectious disease physician and professor of internal medicine at the Northeast Ohio Medical University, told Verywell that the situation is a bit different for adults because they “have more preexisting antibodies, which can inhibit vaccine responses."

Given the difference in immune responses, Watkins said that “it might be easier to develop a universal flu vaccine for children than adults.”

Infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, told Verywell that “the point is that annual flu vaccine induces antibodies that are broadly neutralizing.”

Adalja stressed that adults still do get benefits and antibodies from the vaccine, and that “it may be that children get more as their immune systems have not been primed” to respond to the virus the way adults have through continued exposure through vaccination and infection.

Russo said the study demonstrates the importance of adults and children getting their annual flu shot.“

We don’t want the take-home message to be that it’s futile for adults to get vaccinated against the flu—that’s not true,” said Russo. “Everyone who is able should get their annual flu vaccine.”