This study used real world data from the National COVID Cohort Collaborative database in America to look at the risk of breakthrough COVID-19 infections in cancer patients who have been vaccinated. They compared these patients with people without cancer. Patients with both solid tumours and blood cancers were at significantly higher risk of COVID-19 infection and severe outcomes, even after being vaccinated. However, the risk for solid cancers was much less than for blood cancers.
A second dose of the COVID-19 vaccine reduced the risk, particularly in patients with multiple myeloma. Patients with blood cancer, patients on immunosuppressive medications, and those undergoing bone marrow transplants were at the highest risk for breakthrough infection after being vaccinated.
The findings from this real world study provide evidence that patients with cancer are at a higher risk for breakthrough COVID-19 infection after being vaccinated, and a second vaccination significantly reduces this risk. The effects on the outcomes of these patients were less clear.