SARS-CoV-2-reactive antibody waning, booster effect and breakthrough SARS-CoV-2 infection in hematopoietic stem cell transplant and cell therapy recipients at one year after vaccination

The kinetics of SARS-CoV-2 reactive IgG antibodies after full vaccination and booster in allogeneic and autologous stem cell transplantation (allo-HSCT, ASCT) and chimeric antigen receptor T-cell therapy (CAR-T) are of utmost importance for estimating risk of infection. A prospective multicenter registry-based cohort study, conducted from December 2020 to July 2022 was used to analyze antibody waning over time, booster effect and the relationship of antibody response and breakthrough infection in 572 recipients (429 allo-HSCT, 121 ASCT and 22 CAR-T cell therapy). A significant decline in antibody titers was observed at 3 and 6 months after full vaccination in recipients without pre-vaccine SARS-CoV-2 infection, whereas recipients infected prior to vaccination showed higher and stable antibody titers over time. In poor responders, a booster dose was able to increase antibody titers in 83% of allo-HSCT and 58% of ASCT recipients but not in CART-T cell recipients [0%] (p < 0.01). One-year cumulative incidence of breakthrough infection was 15%, similar among cell therapy procedures. Immunosuppressive drugs at the time of vaccination [hazard ratio (HR) 1.81, p = 0.0028] and reduced intensity conditioning (HR 0.49, p = 0.011) were identified as the only conditions associated with different risk of breakthrough infection in allo-HSCT recipients. Antibody titers were associated with breakthrough infection and disease severity. No death was observed among the 72 breakthrough infections. Antibody level decay after the first two vaccine doses was common except in recipients with pre-vaccination SARS-CoV-2 infection. Poorly responding allo-HSCT recipients showed a response advantage with the booster as compared to ASCT and, especially, the null response found in CAR-T cell recipients. Antibody titers were positively correlated with the risk of breakthrough SARS-CoV-2 infection which was mainly driven by the immunosuppression status.

SARS-CoV-2 vaccine response and rate of breakthrough infection in patients with hematological disorders

Background

The clinical efficacy of SARS-CoV-2 vaccines according to antibody response in immunosuppressed patients such as hematological patients has not yet been established.

Patients and methods

A prospective multicenter registry-based cohort study conducted from December 2020 to December 2021 by the Spanish transplant and cell therapy group was used to analyze the relationship of antibody response at 3–6 weeks after full vaccination (2 doses) with breakthrough SARS-CoV-2 infection in 1394 patients with hematological disorders.

Results

At a median follow-up of 165 days after complete immunization, 37 out of 1394 (2.6%) developed breakthrough SARS-CoV-2 infection at median of 77 days (range 7–195) after full vaccination. The incidence rate was 6.39 per 100 persons-year. Most patients were asymptomatic (19/37, 51.4%), whereas only 19% developed pneumonia. The mortality rate was 8%. Lack of detectable antibodies at 3–6 weeks after full vaccination was the only variable associated with breakthrough infection in multivariate logistic regression analysis (Odds Ratio 2.35, 95% confidence interval 1.2–4.6, p = 0.012). Median antibody titers were lower in cases than in non-cases [1.83 binding antibody units (BAU)/mL (range 0–4854.93) vs 730.81 BAU/mL (range 0–56,800), respectively (p = 0.007)]. We identified 250 BAU/mL as a cutoff above which incidence and severity of the infection were significantly lower.

Conclusions

Our study highlights the benefit of developing an antibody response in these highly immunosuppressed patients. Level of antibody titers at 3 to 6 weeks after 2-dose vaccination links with protection against both breakthrough infection and severe disease for non-Omicron SARS-CoV-2 variants.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01275-7.