, according to a study published in JAMA Oncology.
The risks were highest among patients who had certain cancers and those who had received cancer treatment within the past year.
“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 authors wrote.
Researchers at Case Western Reserve University in Cleveland analyzed electronic health record data for more than 636,000 vaccinated patients, including more than 45,000 vaccinated patients with cancer. They looked for the time trends, risks, and outcomes of breakthrough COVID-19 infections for vaccinated cancer patients in the United States between December 2020 and November 2021.
Overall, the cumulative risk of breakthrough infections in vaccinated cancer patients was 13.6%, with the highest risk for pancreatic (24.7%), liver (22.8%), lung (20.4%), and colorectal (17.5%) cancers and the lowest risk for thyroid (10.3%), endometrial (11.9%), and breast (11.9%) cancers, versus 4.9% in vaccinated patients without cancer.
Patients who had medical encounters for their cancer within the past year had a higher risk for a breakthrough infection, particularly those with breast cancer, blood cancers, colorectal cancer, bladder cancer, and pancreatic cancer.
Among patients with cancer, the overall risk for hospitalization after a breakthrough infection was 31.6%, as compared with 3.9% in those without a breakthrough infection. In addition, the risk of death was 6.7% after a breakthrough infection, as compared with 1.3% in those without a breakthrough infection.
Among patients who didn’t have cancer, the overall hospitalization risk was 25.9% in patients with a breakthrough infection, as compared with 3% in those without a breakthrough infection. The overall risk of death was 2.7% after a breakthrough infection, as compared with 0.5% in those without a breakthrough infection.
In addition, breakthrough infections continuously increased for all patients from December 2020 to November 2021, with the numbers consistently higher among patients with cancer.
“This increasing time trend may reflect waning immunity of vaccines, the emergence of different virus variants, and varied measures taken by individuals and communities over time during the pandemic,” the study authors wrote.
Vaccines are likely less protective against coronavirus infection in cancer patients, and in turn, cancer patients may be more susceptible to COVID-19 infections, the researchers wrote. As breakthrough infections continue to increase for everyone, patients with cancer will face increased risks for severe breakthroughs, hospitalization, and death, they concluded.
A version of this article first appeared on WebMD.com.