Breakthrough COVID-19 cases more likely in cancer and Alzheimer's patients, study finds

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Experts say these conditions may make patients more susceptible to infection

A new study conducted by researchers from Case Western Reserve University explored some of the risk factors associated with breakthrough cases of COVID-19. According to their findings, consumers with cancer or Alzheimer’s may have a higher risk of developing these cases. 

“This study showed significantly increased risks for COVID-19 breakthrough infection in vaccinated patients with cancer, especially those undergoing active cancer care, with marked variations among specific cancer types,” said researcher Rong Xu. 

Identifying breakthrough cases

The researchers conducted two studies to assess the risk that COVID-19 poses to patients with cancer and Alzheimer’s. Both studies analyzed electronic health records of patients who were diagnosed with either cancer or Alzheimer’s and also tested positive for COVID-19 after getting fully vaccinated to protect against the virus. 

The first study analyzed data from over 636,000 vaccinated cancer patients who had one of 12 different types of cancer. The second study looked at anonymous health data from more than 262,000 adults who were vaccinated between December 2020, and August 2021. Among that group, nearly 9,000 participants had been diagnosed with some form of dementia. 

The researchers learned that the risk of a breakthrough COVID-19 case was 13.6% for vaccinated cancer patients; on the other hand, vaccinated people without cancer had a less than 5% risk of a breakthrough case. Certain kinds of cancer posed a greater risk of breakthrough infection, including pancreatic, liver, lung, and colorectal cancer. Patients with thyroid cancer, endometrial cancer, and breast cancer had the lowest risk of having a breakthrough COVID-19 case. 

“Breakthrough infections in patients with cancer were associated with significant and substantial risks for hospitalizations and mortality,” said Xu and researcher Nathan Berger. “These results emphasize the need for patients with cancer to maintain mitigation practice, especially with the emergence of different virus variants and the waning immunity of vaccines.” 

The study on patients with dementia yielded similar results. For those with Alzheimer’s, the risk of a breakthrough infection was 10.3%. In contrast, vaccinated older adults without dementia had a 5.6% risk of breakthrough infection. 

“Patients with dementia have a significantly higher rate of breakthrough COVID infections after vaccination than patients of the same age and risk factors other than dementia,” said researcher Pamela Davis. “Therefore, continued vigilance is needed, even after vaccination, to protect this vulnerable population. Caregivers should consider ongoing masking and social distancing, as well as booster vaccines to protect these individuals.” 

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