COVID Vaccine Studies Reveal Potential Health Risks, but Experts Urge Cautious Interpretation

Two large-scale studies have identified possible health concerns associated with COVID-19 vaccines, including an increased risk of kidney injury and certain respiratory infections. However, medical experts emphasize that these findings require careful interpretation and do not suggest people should avoid vaccination.

A Korean study published in the International Journal of Infectious Diseases examined how infectious disease patterns shifted during and after the pandemic, with particular attention to vaccine impacts. The research revealed dramatic changes in respiratory infection rates following COVID-19.

“While influenza-like illness dropped sharply during the early pandemic, upper respiratory infections and the common cold surged in 2023 and 2024, far above expected levels,” explained lead study author Jihun Song from Korea University College of Medicine. “Most strikingly, pertussis increased more than 40-fold compared to historical trends.”

When analyzing vaccine effects, researchers found individuals who received four or more COVID-19 vaccine doses were less likely to contract flu-like illnesses and whooping cough. However, these same individuals appeared more susceptible to common colds and other mild respiratory infections.

This finding surprised the research team. “We did not expect to see such divergent associations with infectious disease type,” Song noted. “These mixed associations likely reflect complex changes in immunity, behavior and healthcare use in the post-pandemic era.”

Dr. Jacob Glanville, CEO of biotechnology company Centivax, pointed out a significant limitation in the study design. Those who received more vaccines were considerably older (averaging 67 years) than groups with fewer vaccines (averaging 37-47 years). “They need to do age matching and then run the analysis again,” he said. “Obviously, old people go to hospital more for colds and upper respiratory infections.”

The researchers acknowledged that their observational study demonstrates association, not causation. Song emphasized that older adults and people with chronic conditions were more likely to receive booster doses, potentially influencing results. Changes in healthcare-seeking behavior after the pandemic also represented a limitation.

“Our findings should not be interpreted as evidence that the vaccine increases or decreases specific infections, but rather as indicators of population-level trends that require further investigation,” Song cautioned.

A second study, published in the International Journal of Medical Sciences, found that COVID-19 vaccination was associated with elevated risk of acute kidney injury and dialysis within one year post-vaccination. Within 12 months, 15,809 vaccinated individuals developed acute kidney injury compared to 11,081 unvaccinated people. Additionally, 1,513 vaccinated individuals required dialysis within a year, versus 697 unvaccinated people.

Despite these findings, the study also revealed that vaccinated people had lower overall mortality rates. “Both risks were low in absolute terms, but the study is statistically well-controlled and there might be a real signal here,” Glanville noted. “Other studies showed that the risk of renal disease from infection is way higher than from vaccination, which is counterintuitive. This deserves to be looked at further.”

This research also had limitations, including gaps in electronic health record data. The retrospective study design lacked information on vaccine doses, antibody levels, and details about kidney problems, comorbidities, and medication use that might affect kidney function.

Hua Wang, associate professor at the University of Illinois’ Grainger College of Engineering, urges balanced interpretation of these studies. “Both benefits and risks are reported in both studies, so we should not simply highlight the potential negative effects of COVID-19 vaccination,” Wang said. “One potential limitation is the lack of information on SARS-CoV-2 infection rates in vaccinated versus non-vaccinated groups. The effect of the viruses themselves could be significant.”

Dr. Marc Siegel, Fox News senior medical analyst, added perspective on the research findings. “These are massive studies that by no means prove that COVID vaccines cause kidney problems or increase susceptibility to other respiratory infections,” he said. “However, the association found is certainly worth investigating further.”

Siegel also noted potential selection bias: “It is quite possible that the studies were biased if those who took the vaccine were already more prone to other infections or to kidney problems.”

Public health experts continue to recommend COVID-19 vaccination while acknowledging the importance of ongoing safety surveillance and additional research into potential side effects.