Introduction
People with hematologic malignancies (HM) have impaired immune responses following coronavirus 2019 (COVID-19) vaccination, due in part to innate immunosuppression inherent to their disease process, immunosuppressive treatments, and associated comorbidities. We analyzed seroconversion rates following a primary two-dose COVID-19 vaccination series and subsequent seroconversion rates after booster doses across our patient population with various subtypes of HM, HIV infection, and solid tumors.
Methods
We conducted a retrospective study of 305 fully vaccinated adults with hematologic malignancies (N= 237), HIV (N= 47), solid tumors (N= 12), or other (N=11) seen in a single practice between May 2020 and July 2022. A serum spike antibody level ≥0.8U/mL was considered evidence of seroconversion as defined by the manufacturer. We utilized a Mann-Whitney test to analyze continuous variables and a chi-square test to analyze categorical variables.
Results
Seroconversion after initial vaccination was significantly associated with disease category and treatment received. Seroconversion rates were lowest in patients with B-cell lymphomas (44 of 68, 63.9%), and patients receiving anti-B-cell monoclonal antibodies (32 of 62, 51.6%). All patients with HIV or solid tumors (N=57) demonstrated seroconversion after initial vaccination as did 86% of patients with plasma cell dyscrasias (37 of 43).
In patients who had no detectable antibodies after their initial vaccination course (51 of 305, 16%), 25 (49%) had detectable antibodies following one booster dose. There was no significant difference in rate of breakthrough infections in each quartile of neutralizing antibody titer.
Conclusion
In concordance with prior studies, we observed that booster vaccinations can result in detectable antibodies in a significant proportion of patients who were seronegative after their primary COVID-19 vaccination series. This supports the utility of antibody testing to identify vaccine response in high-risk patients. However, we did not find a significant difference in rates of breakthrough COVID-19 infection based on antibody titer. Mature data are needed to identify the role of cellular immunity in COVID-19 vaccination.