[SARS-CoV-2 antibodies after booster vaccination. Identification of subgroups with poor response]

To determine which patients within the high-risk group are most likely to have insufficient post-vaccination immunity.

Determination of IgG titers against SARS-CoV-2 after the booster dose. Vaccine response was categorized as negative (IgG titers < 34 BAU/ml), indeterminate (titers 34 - 259 BAU/ml) or positive (≥ 260 BAU/ml).

765 patients were included (31.25% of those vaccinated). 54 (7.1%) on treatment with biologics, 90 (11.8%) with hematologic disease, 299 (39.1%) with oncologic pathology, 304 (39.7%) with solid organ transplant and 18 (2.4%) with immunosuppression for other reasons. 74 patients (9.7%) had negative serology and 45 (5.9%) had indeterminate titers. By diagnostic group, the patients with the highest proportion of negative or indeterminate serology were patients with biologic treatment (55.6%, mainly at expense of antiCD20), hematologic (35.4%) and transplant patients (17.8%, mainly lung and kidney). Oncology and other immunosuppressed patients had a favorable response to vaccination.

Patients treated with antiCD20 drugs, hematologic patients and transplanted patients (mainly lung and kidney) have a higher risk of not achieving post-vaccination immunity. It is essential to identify them in order to individualize and optimize their management.