Two major studies published this month are raising new questions about potential health risks associated with the COVID-19 vaccine — but researchers and independent experts warn the findings should be interpreted carefully and not taken as proof of harm.
According to Fox News, one study out of Korea, published in the International Journal of Infectious Diseases, examined how patterns of infectious disease shifted during and after the pandemic and whether vaccination played a role.
Lead author Jihun Song, Ph.D., said the research showed a dramatic change in how respiratory illnesses spread.
“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,” Song told Fox News Digital. “Most strikingly, pertussis increased more than 40-fold compared to historical trends.”
The study found that people who received four or more vaccine doses were less likely to contract flu-like illnesses and whooping cough, but more likely to get common colds or other mild respiratory infections.
“We did not expect to see such divergent associations,” Song said. “These mixed associations likely reflect complex changes in immunity, behavior, and healthcare use in the post-pandemic era.”
Experts caution, however, that such results do not show causation. Dr. Jacob Glanville, CEO of Centivax, noted that the group receiving the most doses was significantly older — averaging 67 years old — which naturally increases the likelihood of hospital visits for respiratory symptoms.
“They need to do age matching and then run the analysis again,” Glanville said. “Obviously, old people go to the hospital more for colds and upper respiratory infections.”
Song and his team emphasized that the study was observational. Older adults and those with chronic illness were more likely to receive boosters, and changes in “care-seeking behavior” after the pandemic may have influenced diagnosis rates.
The researchers also did not collect immunological data — such as antibody levels — leaving unanswered questions about whether changes in immunity played a role.
A second study, published in the International Journal of Medical Sciences, examined whether vaccination was associated with acute kidney injury. Researchers reported that within one year, 15,809 vaccinated people developed acute kidney injury compared with 11,081 unvaccinated people.
Dialysis rates were also higher among the vaccinated. However, the study found that vaccinated individuals had lower all-cause mortality.
“Both risks were low in absolute terms, but there might be a real signal here,” Glanville said. He noted that previous research has shown the risk of kidney complications from COVID infection is far higher than any risk potentially associated with vaccination.
Like the Korean study, researchers acknowledged limitations, including gaps in medical records and the inability to account for vaccine dosage, antibody response, underlying conditions, and common medications that can affect kidney function.
Hua Wang, an associate professor at the University of Illinois, urged people not to overreact to early findings.
“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. He added that the studies lacked information on how many participants had actually been infected with the virus — a major factor in assessing health outcomes.
Other experts echoed that message, stressing that the results do not prove vaccines increase respiratory infections or kidney issues.
“These are massive studies that by no means prove that COVID vaccines cause kidney problems or increase the susceptibility to other respiratory infections,” one expert told Fox News Digital. “The association found is certainly worth investigating further.”
He added that it remains possible that those who took the vaccine “were already more prone to other infections or to kidney problems,” which could skew the findings.
Researchers behind both studies called for continued monitoring of post-pandemic disease trends, emphasizing that the landscape of respiratory illness now looks fundamentally different than before 2020.
