Longer-term response to SARS-CoV-2 vaccination after allogeneic blood stem cell transplantation

Recipients of allogeneic haematopoietic stem cell transplantation (alloHSCT) are at increased risk of COVID-19 and lower vaccine immunogenicity. This study assessed vaccine immunogenicity and safety in these patients.

We analyzed the serological response after the 2nd and 3rd SARS-CoV-2 vaccination as well as potential factors influencing this response. Data were obtained from internal hospital records. In addition, a questionnaire was used to evaluate the vaccination status, vaccination side effects and the course of expired COVID-19 disease.

In total, 114 patients (median age 62, range 27 - 70) were enrolled between July and September 2022, with 55 females (48.2%). One year later a follow up was conducted. Most patients (89.4%) were vaccinated at least twice, 66.7% received three vaccinations, and 10.5% refused the vaccination. The mRNA vaccines were predominantly used. Most patients responded and reached SARS-CoV-2 spike IgG titers after the 2nd (81.8%) or 3rd (96.1%) vaccination. Patients vaccinated within 24 months of alloHSCT had significantly lower anti-spike IgG levels than those vaccinated later (p=0.017). Common side effects included arm pain (34%), swelling (14%), and limb pain (17%).

Vaccination was feasible and well-tolerated in alloHSCT recipients. Timing of vaccination influenced immune response, with a stronger response after the 3rd dose compared to the initial series.