Impact of SARS-CoV-2 spike antibody positivity on infection and hospitalisation rates in immunosuppressed populations during the omicron period: the MELODY study.

Background: In the UK, booster COVID-19 vaccinations have been recommended biannually to people considered immune vulnerable. We investigated, at a population level, whether the absence of detectable anti-SARS-CoV-2 spike protein IgG antibody (anti-S Ab) following three or more vaccinations in immunosuppressed individuals was associated with greater risks of infection and severity of infection.

Methods: In this prospective cohort study using UK national disease registers, we recruited participants with solid organ transplants (SOTs), rare autoimmune rheumatic diseases (RAIRDs), and lymphoid malignancies. All participants were tested for anti-S Ab using a lateral flow immunoassay, completed a questionnaire on sociodemographic and clinical characteristics, and were followed up for 6 months using linked data from the National Health Service in England. SARS-CoV-2 infection was primarily defined using UK Health Security Agency data and supplemented with hospitalisation and therapeutics data, and hospitalisation due to SARS-CoV-2 was defined as an admission within 14 days of a positive test.

Findings: Between Dec 7, 2021, and June 26, 2022, we recruited 21 575 participants. Anti-S Ab was detected in 6519 (77·0%) of 8466 participants with SOTs, 5594 (85·9%) of 6516 with RAIRDs, and 5227 (79·3%) of 6593 with lymphoid malignancies. COVID-19 infection was recorded in 3907 (18·5%) participants, with 556 requiring a COVID-19-related hospital admission and 17 dying within 28 days of infection. Rates of infection varied by sociodemographic and clinical characteristics but, in adjusted analysis, having detectable anti-S Ab was independently associated with a reduced incidence of infection, with incident rate ratios (IRRs) of 0·69 (95% CI 0·65-0·73) in the SOT cohort, 0·57 (0·49-0·67) in the RAIRD cohort, and 0·62 (0·54-0·71) in the lymphoid malignancy cohort. In adjusted analysis, having detectable anti-S Ab was also associated with a reduced incidence of hospitalisation, with IRRs of 0·40 (0·35-0·46) in the SOT cohort, 0·32 (0·22-0·46) in the RAIRD cohort, and 0·41 (0·29-0·58) in the lymphoid malignancy cohort.

Interpretation: All people with immunosuppression require ongoing access to COVID-19 protection strategies. Assessment of anti-S Ab responses, which can be performed at scale, can identify people with immunosuppression who remain most at risk, providing a mechanism to further individualise protection approaches.

Funding: UK Research and Innovation, Kidney Research UK, Blood Cancer UK, Vasculitis UK, and Cystic Fibrosis Trust.