COVID vaccine under new scrutiny after studies reveal possible health risks
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Two large studies have highlighted the potential health risks of the COVID vaccine, but some experts recommend caution when interpreting the findings.
Recent research has linked the vaccine to an increased risk of kidney injury, as well as certain respiratory infections.
A Korean study published in the International Journal of Infectious Diseases looked at how infectious diseases changed during and after the COVID-19 pandemic, as well as the impact of vaccines.
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“While influenza-like illnesses decreased dramatically during the first pandemic, upper respiratory infections and the common cold increased in 2023 and 2024, well above expected levels,” the study’s lead author, Jihun Song, Ph.D., of the Department of Biomedical Informatics at Korea University School of Medicine, told News Digital.
“The most surprising thing is that whooping cough increased more than 40 times compared to historical trends.”
Recent research has linked the vaccine to an increased risk of kidney injury, as well as certain respiratory infections. (iStock)
“The key message is that respiratory infections in Korea changed dramatically after the COVID-19 pandemic, and the patterns differ by disease.”
When researchers looked at the impact of the COVID vaccine, they found that people who received four or more doses were less likely to get flu-like illnesses and whooping cough, but more likely to get common colds and other mild respiratory infections.
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“We did not expect to see such divergent associations with the type of infectious disease, where some infections (influenza-like illnesses) decreased among vaccinated individuals, while others (the common cold) increased,” Song said. “These mixed associations likely reflect complex changes in immunity, behavior, and healthcare use in the post-pandemic era.”
People who received four or more doses of the COVID-19 vaccine were less likely to get flu-like illnesses and whooping cough, but more likely to get common colds and other mild respiratory infections, the researchers said. (AP Photo/Steve Helber, File)
Dr. Jacob Glanville, CEO of Centivax, a San Francisco biotechnology company, said the most vaccinated group was older, averaging 67 years old, while the least vaccinated groups averaged 37 to 47 years old.
“They need to do an age comparison (called controlling for confounding variables) and then run the analysis again,” Glanville, who was not involved in the study, told News Digital. “Obviously, older people go to the hospital more for colds and upper respiratory infections.”
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The researchers noted that because the study was observational, it does not prove that the vaccine caused the increase in infections, but only shows an association.
Additionally, older adults and people with chronic illnesses are more likely to receive booster doses, which may influence the results, Song noted.
Changes in “care-seeking behavior” and medical use patterns pose another limitation, he said. “After years of reduced healthcare use, people may visit clinics differently than before, affecting diagnosis rates.”
In a recent study, COVID-19 vaccination was associated with an increased risk of acute kidney injury and dialysis within one year, although vaccinated people had lower rates of death from all causes. (iStock)
The researchers also did not collect immunological data, such as antibody levels or immune cell activity, meaning they could not say whether the effects were due to biological immune responses or external factors.
“The findings could be influenced by differences in age, underlying diseases and health care utilization between the vaccinated and unvaccinated groups,” Song said.
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He emphasized that the study does not mean people should avoid the COVID vaccine.
“Instead, it highlights the need to raise awareness about the increase in respiratory infections to encourage timely diagnosis and appropriate preventive measures. [as well as] “Surveillance of respiratory pathogens has been strengthened, as the post-COVID landscape is fundamentally different from before,” Song said.
“While influenza-like illnesses decreased dramatically early in the pandemic, upper respiratory infections and the common cold increased in 2023 and 2024, well above expected levels,” said one researcher. (iStock)
“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.”
In another recent study published in the International Journal of Medical Sciences, COVID-19 vaccination was associated with an increased risk of acute kidney injury and dialysis within one year, although vaccinated people had lower rates of death from all causes.
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In 12 months, 15,809 vaccinated people developed acute kidney injury, compared to 11,081 unvaccinated people.
A total of 1,513 people received dialysis one year after vaccination, compared to 697 unvaccinated people.
“Both risks were low in absolute terms, but the study is well controlled statistically and there could be a real signal here,” Glanville told News Digital.
“Other studies have shown that the risk of kidney disease from infection is much higher than from vaccination, which is counterintuitive,” he continued. “This deserves further analysis.”
The study also had limitations, the researchers acknowledged.
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These included gaps in data in electronic medical records: They lacked information on vaccine doses and antibody levels, as well as details on kidney problems, other health conditions and over-the-counter medications that can affect the kidneys.
Because this was a retrospective study and not a controlled trial, differences between the groups may have influenced the results.
“Both studies report benefits and risks.”
Hua Wang, associate professor of materials science and engineering at the University of Illinois Grainger College of Engineering, encourages people to be careful when interpreting data in this type of research.
“Both studies report both benefits and risks, so we should not simply highlight the potential negative effects of COVID-19 vaccination as some news articles claim,” said Wang, who was not involved in the studies.
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“A possible limitation of the two studies is the lack of information on the fraction of participants diagnosed with the SARS-COVID-2 virus in the vaccinated and unvaccinated groups,” the professor added. “The effect of the viruses themselves, as we know, could be significant.”
One expert noted that the group that received the most vaccinations was older, with an average of 67 years old, while the groups with the least vaccinations were an average of 37 to 47 years old. (iStock)
Dr. Marc Siegel, News senior medical analyst and author of the new book “The Miracles Among Us” (News Books), also commented on the research.
“These are massive studies that in no way prove that COVID vaccines cause kidney problems or increase susceptibility to other respiratory infections, including the flu,” he told News Digital.
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“However, the association found is worth investigating further, and sheds light on the fact that immune pump priming should be followed carefully to consider potential effects.”
Siegel added: “It’s also very possible that the studies were biased if those who took the vaccine were already more prone to other infections or kidney problems.”
Melissa Rudy is a senior health editor and member of the lifestyle team at News Digital. Story tips can be sent to melissa.rudy@News.com.