A new study by a team from Imperial College London has shown that immune responses to the COVID-19 vaccine in people with chronic myeloid leukaemia treated with tyrosine kinase inhibitors are similar to those in people without the illness.
The researchers set out to assess immunity after COVID-19 vaccination in 62 people with chronic myeloid leukaemia, who were being treated with tyrosine kinase inhibitors. These are a type of targeted anticancer therapy that stops or slows the bone marrow making abnormal white blood cells, and is the primary treatment for chronic myeloid leukaemia.
The data from this group was compared with those for 44 people without the illness. The results were published in the Nature journal Leukemia.
Participants received two doses of either the AstraZeneca or Pfizer vaccine followed by a third Pfizer dose. The researchers measured T cell and B cell responses at different timepoints after the first, second and third COVID-19 vaccine dose.
It has until now been unclear how well people with chronic myeloid leukaemia mount a protective immune response against COVID-19 after vaccination. Responses to influenza or pneumococcal vaccination have been found to be impaired in people being treated with tyrosine kinase inhibitors for chronic myeloid leukaemia, and the researchers predicted that antibody responses would be impaired in this group after the COVID-19 vaccine, while the T cell response would remain intact.
However, what they actually found was that both antibody and T cell responses were largely the same in the group with chronic myeloid leukaemia as in the control group. A third vaccine dose significantly improved T cell responses in both groups compared to after the first dose.
This suggests that the potent activation of immune pathways by mRNA and adenoviral vectored vaccines is largely able to overcome the B cell deficits previously observed in this group after pneumococcal or influenza vaccines.
They also found that people in this group had similar cross-recognition of Omicron to the control group. Antibody boosting after a third vaccine dose was equally effective in both groups.
The study team concluded that people with chronic myeloid leukaemia treated with tyrosine kinase inhibitors would not have been exceptionally vulnerable during the first waves of the pandemic, as they had good immune responses after three doses of COVID-19 vaccine.
However, they stressed the importance of booster vaccine doses in vulnerable populations (such as those with chronic myeloid leukaemia) in order to ensure adequate protection from severe disease, hospitalisation and death.