The number of Americans willing to get a flu shot declined during the pandemic, as many who received the vaccine appeared to get sick, and concerns grew over possible side effects. 

In response to declining numbers, the Centers for Disease Control and Prevention (CDC) on Sep. 11 rolled out a digital ad campaign it hopes will encourage vaccine-hesitant people to get the shot, even if they get sick.

The CDC’s new messaging is simple: The flu shot won’t keep someone from getting sick but can “tame” wild flu symptoms into mild flu symptoms in those who get the vaccine but still get sick.

The “Wild to Mild” campaign is part of the agency’s efforts to rebrand expectations about what yearly influenza vaccines can and can’t do and provides a campaign toolkit with infographics, animated images, social media marketing materials, and other online resources people can use to encourage their “friends, loved ones, and followers on social media” to get vaccinated. 

This is similar to the marketing strategy U.S. regulatory agencies used with COVID-19 vaccines. After Americans started experiencing breakthrough infections, U.S. health officials admitted the shots did not prevent COVID-19 or transmission of the virus to others, and vaccine efficacy was re-defined by whether the vaccine prevented hospitalization and death to make it look more effective.

Dr. Bill Schaffner, an infectious disease specialist at Vanderbilt University and member of the CDC’s advisory panel on vaccines, told CNN he believes the agency is on the right track. 

“With these respiratory viruses, flu included, the vaccines aren’t very good at preventing milder disease. They’re much better at preventing serious complications. And I think we have not been very clear in presenting that information,” Schaffner said. “We have to acknowledge that. We have to say, ‘Yep, it won’t prevent that mild disease. But here’s the benefit.’”

Ads for the new campaign have already begun rolling out on radio and social media platforms targeting pregnant women and parents of young children, as vaccination rates have declined in these high-risk groups. 

Safety of Flu Shots in Pregnant Women

According to the National Foundation of Infectious Diseases, flu vaccination coverage decreased by 6 points to 58% among children and adolescents ages 6 months to 17 years during the 2021-2022 flu season. 

Vaccination coverage dropped among pregnant women to 50% from 55% during the same period and has dropped 16.6 percentage points since the start of the pandemic in March 2020.

The CDC’s safety data on flu vaccines during pregnancy consists of a handful of studies carried out by the agency between 2011 and 2014. The CDC lists two studies on its webpage that assessed the risks of influenza vaccines in newborns, with the most recent 2020 study using data between 2007 and 2015.

Although the CDC says most influenza vaccines will be thimerosal-free or thimerosal-reduced vaccines, some options do contain this controversial ingredient. Although the CDC claims that thimerosal was taken out of U.S. pediatric vaccines in 2001, up to 25 micrograms of thimerosal remain in many of the influenza vaccines, including those administered to pregnant women and infants.

Thimerosal is a mercury-based preservative in some U.S. vaccines and is associated with very severe neurological disorders, even in trace amounts. Although the CDC continues to adhere to the view that thimerosal is safe, hundreds of peer-reviewed scientific publications demonstrate broad consensus among research scientists that thimerosal is a dangerous neurotoxin. 

Years of Data Show Flu Shots Don’t Work 

According to the CDC, all flu vaccines for the 2023-2024 season will be quadrivalent vaccines, meaning they will contain strains designed to target four different flu viruses. The new quadrivalent flu shot is just one of three vaccines coming down the line the CDC is encouraging people to get this fall. 

The agency is recommending updated COVID-19 vaccines—recently authorized by the U.S Food and Drug Administration without clinical data—flu shots for individuals 6 months of age and older, and the new RSV (respiratory Syncytial Virus) vaccine.

The CDC has not provided data showing it is safe to co-administer these vaccines, including to the most vulnerable populations, such as immunocompromised and pregnant women. 

The CDC each year conducts its own studies to determine how well influenza vaccines protect against the flu and uses those and previous studies to support the statements it makes about influenza vaccine effectiveness. 

Factors affecting vaccine efficacy depend on which flu viruses are circulating and how well-matched those viruses are to flu vaccines. According to the agency, flu vaccine effectiveness ranged from 10% to 54% effective between 2004 and 2023, when flu shot effectiveness was based on flu prevention.

In a CDC study published in September 2023 in its Morbidity and Mortality Weekly Report, a research team from the CDC analyzed data on 2,780 patients hospitalized with severe acute respiratory infection from five South American countries from March to July 2023.

The researchers determined the 2023 Southern Hemisphere seasonal influenza vaccine reduced the risk of influenza-associated hospitalizations by 52%, with an estimated protection of 55% against the predominant A(H1N1) strain. Because circulating viruses are genetically similar to those in the Northern Hemisphere, they assumed the formulation may offer equal protection. 

This is the only recent study the CDC is using to support its recommendations. The agency says other studies show influenza vaccination reduces the risk of illness by 40% to 60% among the overall population during seasons when most circulating flu viruses are well-matched to the strains used to make flu vaccines—but these studies are decades old and utilize entirely different influenza vaccines.