Characteristics of virus-specific immunological reactions following COVID-19 vaccination in heart transplant recipients

Heart transplant patients are at an increased risk of COVID-19 infection adverse outcomes because of underlying immunosuppression and concomitant comorbidities. To date, all large-scale randomized controlled trials for various COVID-19 vaccines have excluded solid organ transplant recipients. Therefore, the efficacy and safety of coronavirus infection prevention using COVID-19 vaccines in transplant heart patients has not been sufficiently studied. In this research, the evaluation of virus-specific immunological reactions after vaccination (double Vero Cell vaccination and Sputnik Light booster vaccination) in heart transplant patients has been carried out. In vaccinated heart transplant individuals who did not have a history of COVID-19, starting from 4–6 months after the 2nd dose of the vaccine, an increase in antibodies to S protein level of was observed, while maintaining statistically significant differences for 9–12 months after vaccination (regardless of whether with or without booster vaccination). However, the concentration of antibodies remained low, and 37% of patients detected no antibodies. In vaccinated heart transplant individuals following the previous COVID-19 infection, as compared to seronegative patients, post-vaccination immunity is accompanied by maintaining a high level of virus-specific IgG antibodies to the S protein of the SARS-CoV-2 virus in the dynamics of the post-vaccination period with a statistically significant increase of these antibodies by 9–12 months after booster vaccination. The specific cellular response (according to the assessment of CD3⁺154⁺ and CD3⁺IFNγ⁺ TNFα⁺ cells) to the S protein of the SARS-CoV-2 virus remained low throughout the entire follow-up period, was recorded in 5–40% of heart transplant patients and statistically significant changes in the number of spikereactive lymphocytes were observed in patients with a history of COVID-19 by 4–6 months after administration of the 2nd dose of the vaccine. This, together with the results of the assessment of the humoral response, indicates a more pronounced post-vaccination immunity in patients with a hybrid immunity. While developing a methodology for assessing the risk and benefit of a vaccination strategy for individual heart transplant patients, clinical efficacy, ongoing monitoring of rare serious adverse events, and data on vaccine immunogenicity should be taken into account.