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Cancer and dementia patients more at risk from breakthrough Covid-19

  • 24 May 2022

Even when vaccinated, cancer and dementia patients are at a higher risk of contracting the coronavirus.

Even when vaccinated, cancer and dementia patients are at a higher risk of contracting the coronavirus. ( Sukanya Sitthikongsak / Getty Images )

Two new studies from researchers at the Case Western Reserve University School of Medicine suggest that breakthrough Covid-19 cases “resulting in infections, hospitalisations and deaths” are “significantly more likely” in cancer and Alzheimer’s patients.

People suffering from cancer and Alzheimer’s disease are often more susceptible to infection in general, the researchers say. They are also the US population’s most vulnerable to severe health outcomes from Covid-19.

In the United States alone, the total of Covid deaths has surpassed one million people, whereas in the world there have been more than six million deaths from the pandemic.

What are Covid-19 infection rates in cancer patients?

Researchers published a study in the Journal of the American Medical Association (JAMA) Oncology that went through electronic health records to find out how prevalent Covid-19 was in vaccinated patients with cancer, looking at the number of infections, hospitalisations and mortality rates.

The US Centers for Disease Control and Prevention (CDC) explains that “since vaccines are not 100 percent effective at preventing infection, some people who are fully vaccinated will still get COVID-19,” defining vaccine breakthrough infection as “an infection of a fully vaccinated person.”

The research team looked at twelve kinds of cancer: bladder, breast, colorectal, endometrial, hematologic, kidney, liver, lung, pancreatic, prostate, skin, and thyroid.

The cancer patients in the study received vaccinations between December 2020 and November 2021 and had not been infected with Covid-19 before they received their shots. The control group consisted of vaccinated individuals who did not have cancer.

Overall, the researchers went through the records of more than 636,000 vaccinated patients, including more than 45,000 with cancer, comparing breakthrough Covid-19 infections between subjects with cancer and without, “matching for comorbidities, social determinants of health, age and gender, and other demographics,” a news release announces.

"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,” says Rong Xu, professor of biomedical informatics at the School of Medicine and coauthor of this study.

According to the news release, the team found that:

  • The overall risk of breakthrough Covid-19 infections in vaccinated people with cancer was 13.6 percent, compared to 4.9 percent for vaccinated people without cancer.
  • The highest risk of breakthrough infections was in people with pancreatic cancer at 24.7 percent, liver cancer 22.8 percent, lung cancer 20.4 percent and colorectal cancer 17.5 percent.
  • Cancers with lower risk of breakthrough infections included thyroid 10.3 percent, endometrial 11.9 percent, and breast 11.9 percent.
  • The overall risk for hospitalization following a breakthrough infection, in study participants with cancer, was 31.6 percent, compared to a rate of 3.9 percent in those without cancer.
  • The risk of death was 6.7 percent following a breakthrough infection, compared to 1.3 percent in patients without cancer.

“Breakthrough infections in patients with cancer were associated with significant and substantial risks for hospitalizations and mortality. 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,” say Xu and study coauthor, Nathan Berger, the Hanna-Payne Professor of Experimental Medicine at the School of Medicine.

How do Alzheimer’s patients fare after being infected with Covid-19?

A second, separate study by Case Western Reserve University School of Medicine was published in the journal Alzheimer’s & Dementia. Researchers sifted through electronic health data to examine the incidence rate of breakthrough Covid-19 infections in people diagnosed with some subtypes of dementia.

The researchers chose to explore the occurrence of breakthrough Covid-19 cases in dementia patients because they observed that older adults with dementia were underrepresented in vaccine clinical trials. Regardless of how effective the vaccines were on the general population, breakthrough cases still happened.

The study notes that in the clinical trial for the Pfizer-BioNTech vaccine, the median age for the 37,706 participants was 52 years and included only 18 people with dementia, a very minor segment of the trial (0.05 percent).

The subjects chosen for the study did not have Covid-19 before being vaccinated between December 2020 and August 2021. The researchers examined anonymous health data from more than 262,847 adults 65 and older; 2,764 people were diagnosed with Alzheimer’s disease, while 1,244 were diagnosed with vascular dementia, 259 with Lewy body dementia, 229 with frontotemporal dementia, and 4,385 with mild cognitive impairment.

The research focused on the overall risks of breakthrough infections in vaccinated patients, comparing results between those without any cognitive impairment to those with dementia.

The findings showed dramatic differences between dementia patients and those without any cognitive impairment. “Vaccinated patients with dementia had an overall risk for breakthrough infections ranging from 10.3% for Alzheimer’s disease to 14.3% for Lewy body dementia, significantly higher than the 5.6% in the vaccinated older adults without dementia,” the news release notes.

“Patients with dementia have a significantly higher rate of breakthrough [Covid-19] infections after vaccination than patients of the same age and risk factors other than dementia,” says Pamela Davis, the Arline H. and Curtis F. Garvin Research Professor at the School of Medicine.

“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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