Has the COVID-19 Pandemic Impacted Flu Shot Uptake?

Leading researchers recently hypothesized that Covid-19 vaccination rates could be associated with influenza vaccination rates.

In a Correspondence published by The New England Journal of Medicine on June 15, 2022, these researchers based at the UCLA Health Services used nationally representative data from the U.S. Centers for Disease Control and Prevention (CDC) to calculate changes in influenza vaccine uptake at the state-population level during the pandemic, after Covid-19 vaccines became widely available (September 2021 through January 2022) relative to before the pandemic (September 2019 through January 2020).

To account for pandemic-related factors unrelated to Covid-19 vaccines that might affect changes in influenza vaccine uptake, they also compared September 2020 through January 2021 activity.

They stratified changes in influenza vaccine uptake according to the quartile of state-level cumulative Covid-19 vaccine uptake through January 2022. This sensitivity analysis found influenza vaccine uptake remained relatively stable during the first influenza season of the pandemic.

During the first pandemic year, flu shot rates held steady.

While during the second pandemic year, when COVID-19 vaccines were widely available, flu shot rates fell about 4.5% points (from 43.7% to 39.2%) in states with below-average COVID-19 vaccination rates.

In contrast, there was a positive impact on flu vaccination in states with strong COVID-19 vaccine uptake, with an increase of 3.8% points (from 49.0% to 52.8%).

From a regional perspective, after Covid-19 vaccines became widely available (2021–2022 season), adult influenza vaccine uptake decreased within states in the bottom two quartiles of Covid-19 vaccine uptake:

• quartile 1, from 43.7% to 39.2%; 
• quartile 2, from 45.5% [95% CI, 42.8 to 48.2] to 43.5% [95% CI, 40.4 to 46.7]); and increased within states in the top two quartiles:
• quartile 3, from 46.9% [95% CI, 45.1 to 48.8] to 47.7% [95% CI, 45.1 to 50.4]; 
• quartile 4, from 49.0% [95% CI, 46.7 to 51.4] to 52.8% [95% CI, 50.2 to 55.3]).

'Although inferences about specific policies and messaging promoting Covid-19 vaccination are beyond the scope of this ecologic study, these findings suggest that after the widespread availability of Covid-19 vaccines, factors associated with Covid-19 vaccination rates may have spilled over to affect influenza vaccination rates,' stated these researchers.

"It is alarming that controversy surrounding Covid-19 vaccination may be undermining separate public health efforts that save thousands of lives each year," says the study's lead author Richard Leuchter, MD, a resident physician at UCLA Health and the David Geffen School of Medicine, in a press release. 

"Many Americans who never before declined a routine, potentially life-saving vaccine have started to do so."

"This supports what I have seen in my clinical practice and suggests that information and policies specific to Covid-19 vaccines may be eroding more general faith in medicine and our government's role in public health."

As of June 15, 2022, the CDC's data indicates about 592 million Covid-19 vaccines have been administered to over 260 million people. 

During this time, influenza vaccine distribution decreased from about 193 million vaccines in the 2020-2021 flu season to about 175 million vaccines this year.

In addition, during the 2020–2021 and 2021–2022 influenza seasons, influenza vaccine uptake decreased uniformly among children.

In a real-world update, the CDC reported on April 22, 2022, flu vaccination coverage for children six months to 17 years:

• 2% points lower for all children this season as of the week ending April 9, 2022, compared with last season (55.3% compared to 57.3%) and,
• 6.9% points lower this season than the week ending April 11, 2020 ('pre-pandemic 2019-20 season).

As the USA prepares for the 2022-2023 flu season, industry sources indicate an ample supply of various influenza vaccines will be available at local pharmacies and clinics beginning in August 2022.

Furthermore, the CDC fully supports the co-administration of flu shots and Covid-19 vaccines.

As of April 2022, 'the routine administration of all age-appropriate doses of vaccines simultaneously is recommended for children for whom no specific contraindications exist at the time of the visit,' says the CDC. 

This research was supported by grants from the National Institutes of Health (NIH), National Heart, Lung, and Blood Institute, Stimulating Access to Research in Residency program at UCLA (5R38HL143614-03, to Dr. Leuchter); the NIH, National Center for Advancing Translational Sciences UCLA Clinical and Translational Science Institute (UL1TR001881, to Dr. Sarkisian); the NIH, National Institute on Aging (1K76AG064392-01A1, to Dr. Mafi); and the NIH, National Institute on Aging Midcareer Award in Patient-Oriented Aging Research (2K24AG047899-06, to Dr. Sarkisian). Dr. Sarkisian was also supported with resources and the use of facilities at the Veterans Affairs Greater Los Angeles Healthcare Center.

Study communications: Richard K. Leuchter, M.D. [email protected]. 

PrecisionVaccinations publishes fact-checked, research-based vaccine news curated for mobile readers. Dr. Carlson reviewed and edited this article for data clarity.