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Autologous haematological stem cell transplantation (AHSCT) for rapidly progressive severe systemic sclerosis (SSc) is the only treatment, so far, allowing long-term improvement in overall and event-free survival.1 2 The COVID-19 pandemic has challenged experts regarding decisions on AHSCT in these high-risk patients.3 Increased risk for severe COVID-19 infection in SSc is related to lung and heart involvement4 and is enhanced by high-dose immunosuppressive drugs and antithymocyte globulins used for conditioning to eliminate autoreactive cells before AHSCT and to allow reset of tolerance during the immune reconstitution period, lasting around 12 months after transplant.1 3 Several centres have stopped AHSCT activity for SSc during the pandemic for safety considerations. Others decided to continue, believing that the benefit of AHSCT is greater than the risk of severe COVID-19 19 infection. This belief was reinforced with the introduction of SARS-COV-2 vaccines. Current european bone marrow transplantation (EBMT) guidelines recommend vaccination against SARS-COV-2, as early as 3 months after transplantation3 5 .
Israel has been the first country worldwide to implement a national vaccination plan using the Pfizer BNT162b2 vaccine since January 2021 and 85% coverage of the adult population had been obtained in April 2021.
We report herein our experience with SARS-COV-2 vaccination in all seven adult patients with SSc treated by AHSCT in Israel, since we started the programme in 2016, compared with seven sex and aged matched healthy controls. Each patient received two doses of BNT162b2 Pfizer vaccine on days 0 and 21 (table 1), within 3–60 (median 24) months after AHSCT. No adverse reactions were reported, except fatigue lasting 2 days in patient 1.
We measured SARS-COV-2 IgG antibodies by chemiluminescent microparticle immunoassay against s1 s1 subunit of the spike protein using Abbott architect system 2 weeks after the second injection. The seven patients had normal CD20+ cell counts at time of vaccination. All but one patient, transplanted with CD34+ selected AHSCT 3 months before vaccination, who had low (95 cells/mm3) CD4+ T cell count at time of vaccination, mounted a humoral response. All healthy controls mounted a humoral response.
CD4+ TH1-biased T-cells are important for mounting a response after vaccination.6 The use of CD34+ selection favours treatment response but may contribute to the degree and duration of T-cell depletion after transplant which is dependent also on conditioning regimen.1
In conclusion, this report provides the first evidence of efficacy of SARS-COV-2 vaccination after AHSCT for SSc. Only one patient with low CD4 counts (below 200 cells/mm3) after CD34 selection did not mount an immune response to vaccination. Systematic monitoring of immune reconstitution stage and vaccine response after AHSCT is of utmost importance to guide the time frame at which patients should be vaccinated.
Data availability statement
The data underlying this article are available in the article and in its online supplementary material.
Handling editor Josef S Smolen
Contributors All authors took part in collecting data writing and reviewing the letter and approved its final revision for publication.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
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