Polarized views and worries about COVID-19 vaccination had spillover effects on flu vaccination in adults, according to researchers who examined data over two pandemic years on both vaccines by state.
The authors of the study say the findings are a warning of declining trust in public heath, which comes at a vulnerable time as eased COVID-19 measures put populations at risk for the return of disease threats such as flu. Late-season flu activity is still under way in some parts of the United States, and health officials are closely watching Australia, where an early-season surge is already worse than some of the country's pre–COVID pandemic flu seasons.
The group, based at University of California-Los Angeles Health Services, published its findings yesterday in a letter to the New England Journal of Medicine.
Erosion in faith seen in clinical practice
For their observational study, the group looked at Centers for Disease Control and Prevention (CDC) data on uptake for both vaccines though Jan 2022.
During the first pandemic year, flu vaccination rates held steady. In the second pandemic year, however, when COVID-19 vaccines were widely available and promoted, flu vaccination rates fell 4.5 percentage points (from 43.7% to 39.2%) in states with below-average COVID-19 vaccination rates.
In contrast, the researchers saw a positive spillover effect on flu vaccination in states that had strong COVID-19 vaccine uptake, with an increase that averaged 3.8 percentage points (from 49.0% to 52.8%).
Uptake of both vaccines by state were highly variable. For example, for the full COVID-19 vaccination, levels through Jan 2022 ranged from 50% in Alabama to 81% in Rhode Island. For the flu vaccine during the same time, levels ranged from 31% in Mississippi to 59% in Connecticut.
The researchers estimated that a state's COVID-19 vaccination rate could predict 60% of its flu vaccination rate.
The study's lead author, Richard Leuchter, MD, a resident physician at UCLA Health, in a press release aired worries that people who never declined life-saving vaccines before are now foregoing them in the wake of controversy surrounding COVID-19 vaccination.
"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."
Need for understanding uptake, policy lessons
The group wrote that spillovers that either eroded or boosted flu vaccination might be explained by "belief generalization." Leuchter said those who felt compelled to oppose or support COVID-19 vaccination may feel that they should reject or accept other vaccines.
He said, however, that belief generalization goes only so far to account for vaccination trends for kids, which declined for both flu seasons, even in states with high COVID-19 vaccine uptake.
One reassuring finding was that flu vaccination levels remained relatively stable for those 65 years or older, a group at increased risk for complications.
The authors added key caveats, noting that the observational study didn't directly measure people's beliefs or prove that mistrust of vaccines or government drove down flu vaccination rates. They said the findings, though, are alarming and should trigger studies on the root causes of poor COVID-19 vaccination rates, insights that are needed to guide future policies.