Cancer Research UK said the study has not yet been reviewed by other scientists and therefore people undertaking cancer treatment should continue to follow the advice of their doctors.
Martin Ledwick, Cancer Research UK’s head information nurse, said: “We know that this information could be worrying, but anyone undergoing cancer treatment should continue to follow the advice of their doctors, and we encourage all who can to take up the vaccine.”
Blood Cancer UK said: “People with blood cancer will be concerned by this news.
“We have been worried about how much protection the vaccines will give people with blood cancer because vaccines do not usually work as well for people with compromised immune systems.
“This study, while not peer-reviewed and only looking at a small number of people, adds to that concern.
“This means that if you have blood cancer, it is important that you do not assume you have protection even after you have had the vaccine, particularly after just one dose, and that you continue being careful to avoid Covid.