Brussels 04/08/2021
To the Belgian Health Care Authorities,
To the members of the task force,
Position statement of BTS board on 3rd dose of SARS-CoV-2 mRNA vaccine for solid organ transplant recipients.
Severely immunocompromised patients are at high risk of severe forms of Covid-19 with high morbidity and mortality.
For this reason, these patients received priority access to vaccination against SARS-COV-2 in Belgium.
However, the efficacy of standard SARS-COV-2 vaccination in this population is insufficient. Recent data have shown that the proportion of immunocompromised patients developing antibody production against SARS-COV-2 after administration of mRNA-based vaccines is considerably lower than in the general population.
Initial reports have documented that only 10-15% of transplant recipients develop antibodies after the first dose of mRNA vaccines 1,2.
Studies from Belgium, the US and Spain have shown remarkably similar results indicating that only approximately half of organ transplant recipients develop detectable antibodies against SARS-COV-2 after a full course of two doses of the available mRNA vaccines (Moderna or Pfizer Biontech) 3 4 5.
Vaccination early after transplantation and use of potent immunosuppressants were associated with failure to induce antibodies. In addition, antibody titers induced in solid organ recipients under immunosuppression were much lower than in the general population, which raises questions about the strength and duration of the protective immune response.
At least two publications have reported clinically symptomatic COVID-19 in transplant recipients having received a full course of vaccination against SARS-COV-2, leading to hospitalization, intensive care and even death 6,7. In a French cohort with available serology at diagnosis of breakthrough COVID-19 showed that nearly all patients developing clinical symptoms had no detectable antibody response induced after vaccination7.
The available evidence suggests that a third dose of mRNA vaccine can significantly enhance the antibody response in organ transplant recipient with inadequate immunization after a classical course of vaccination8-11.
Based on the available evidence the “Conseil d’Orientation de la Stratégie Vaccinale” in France has adviced on April 6, 2021 to vaccinate all severely immunocompromised patients with a third dose of mRNA vaccine. ( https://solidarites-sante.gouv.fr/IMG/pdf/avis_du_cosv_6_avril_2021pdf.pdf )
The board of the Belgian Transplantation Society recommends to adopt the same approach in Belgium and to provide recipients of solid organ transplants in Belgium with a third dose of mRNA vaccine.
Antibody titers before and after administration of the vaccine should whenever possible be monitored by including these patients in ongoing trials to further validate the efficacy of this strategy.
For the board of the 
Prof Dr Karl Martin Wissing
President of the Belgian Transplantation Society
1. Benotmane I, Gautier-Vargas G, Cognard N, et al. Weak anti-SARS-CoV-2 antibody response after the first injection of an mRNA COVID-19 vaccine in kidney transplant recipients. Kidney Int 2021;99:1487-9.
2. Boyarsky BJ, Werbel WA, Avery RK, et al. Immunogenicity of a Single Dose of SARS-CoV-2 Messenger RNA Vaccine in Solid Organ Transplant Recipients. Jama 2021;325:1784-6.
3. al HGe. Disappointing Immunization Rate after two Doses of the BNT162b2 Vaccine in a Belgian Cohort of Kidney Transplant Recipients. Transplantation 2021;in press.
4. Cucchiari D, Egri N, Bodro M, et al. Cellular and humoral response after mRNA-1273 SARS-CoV-2 vaccine in kidney transplant recipients. Am J Transplant 2021.
5. Boyarsky BJ, Werbel WA, Avery RK, et al. Antibody Response to 2-Dose SARS-CoV-2 mRNA Vaccine Series in Solid Organ Transplant Recipients. Jama 2021;325:2204-6.
6. Ali NM, Alnazari N, Mehta SA, et al. Development of COVID-19 Infection in Transplant Recipients After SARS-CoV-2 Vaccination. Transplantation 2021.
7. Caillard S, Chavarot N, Bertrand D, et al. Occurrence of severe COVID-19 in vaccinated transplant patients. Kidney Int 2021.
8. Werbel WA, Boyarsky BJ, Ou MT, et al. Safety and Immunogenicity of a Third Dose of SARS-CoV-2 Vaccine in Solid Organ Transplant Recipients: A Case Series. Ann Intern Med 2021.
9. Del Bello A, Abravanel F, Marion O, et al. Efficiency of a boost with a third dose of anti-SARS-CoV-2 messenger RNA-based vaccines in solid organ transplant recipients. Am J Transplant 2021.
10. Kamar N, Abravanel F, Marion O, Couat C, Izopet J, Del Bello A. Three Doses of an mRNA Covid-19 Vaccine in Solid-Organ Transplant Recipients. N Engl J Med 2021.
11. Benotmane I, Gautier G, Perrin P, et al. Antibody Response After a Third Dose of the mRNA-1273 SARS-CoV-2 Vaccine in Kidney Transplant Recipients With Minimal Serologic Response to 2 Doses. Jama 2021.