Despite the success of COVID-19 vaccination programmes in reducing morbidity and mortality, a substantial number of individuals in the general population respond poorly to SARS-CoV-2 vaccination. Furthermore, only about 20% of individuals throughout low-income countries have received their first dose of the SARS-CoV-2 vaccine. Neutralising antibodies are a key correlate to protection from COVID-19, with booster vaccines offered to increase protection from new variants. However, poor responsiveness to immunisation increases the risk of infection and disease. The CDC reported that patients with compromised immune systems accounted for about 12% of adult COVID-19 hospital admissions and had higher rates of intensive care admissions and in-hospital deaths compared with non-immunocompromised inpatients, in both vaccinated and unvaccinated populations. Although a heterogeneous group, the majority of patients with immunodeficiency show variable and weaker antibody-mediated responses post-vaccination to SARS-CoV-2 than individuals without immunodeficiency. In March, 2022, a UK report revealed 45·5% of immunocompromised individuals received a booster vaccination dose. However, without immune monitoring it remains unclear which individuals within this high-risk population have sufficient immunity
