Although vaccination is effective for most people who have cancer (even though they’re immunocompromised by the disease and their cancer treatments), its effectiveness wanes more rapidly in this group, by three to six months compared to the general population, new research shows.

The U.K. Coronavirus Cancer Evaluation Project also found that vaccine effectiveness is much lower in people with the blood cancers leukemia or lymphoma, those with a recent cancer diagnosis and those who have received anti-cancer treatment within the last year.

“We know that people with cancer have a higher risk of severe COVID-19 disease and that the immune response in cancer patients following COVID-19 vaccination is lower. However, no study has looked at vaccine effectiveness and its waning in cancer patients at a population level,” said study leader Dr. Lennard Lee, of the University of Oxford oncology department.