IBTK and infection: This can lead to considerable risk of infection with associated morbidity and mortality.10 Infection remains the cause of death for around 25% of patients with CLL.11 12 Most recently, people with CLL were shown to be susceptible to severe COVID-19 and have been prioritised for receiving SARS-CoV-2 vaccines.13–17 Unfortunately, vaccine responses in patients with CLL are impaired, particularly in those on current ‘targeted’ drugs (Bruton tyrosine kinase inhibitors (BTKi)) that act to inhibit B cell receptor function.