key: cord-0855517-5i6sx4r4 authors: Chevallier, Patrice; Jullien, Maxime; Peterlin, Pierre; Garnier, Alice; Le Bourgeois, Amandine; Coste‐Burel, Marianne; Béné, Marie C.; Guillaume, Thierry title: Effectiveness of a third dose of BNT162b2 anti‐SARS‐CoV‐2 mRNA vaccine over a 6‐month follow‐up period in allogenic hematopoietic stem cells recipients date: 2022-04-29 journal: Hematol Oncol DOI: 10.1002/hon.3006 sha: 9c0ba8c5bb5bb243e6e9f7b13ab5984730b0c528 doc_id: 855517 cord_uid: 5i6sx4r4 This study reports the effectiveness of three injections of BNT162b2 anti‐SARS‐CoV‐2 mRNA vaccine in 141 Allo‐HSCT recipients with a median follow‐up of 6 months post‐third shot. We demonstrate a long‐term high protection of Allo‐HSCT recipients since only 2 infections and one death related to COVID‐19 occurred. the same assay, the proportions of good responders remained similar between S1 (81%) and S2 (79%), yet with a slight decrease of IgG titers for 29% of them (Table 1) . Factors associated with good responses were, as expected, 2 a higher lymphocyte (median 2.84 � 10 9 /L vs. 1.00 � 10 9 /L, p = 0.005), CD4+ T cells (median 3.79 � 10 9 /L vs. 2.05 � 10 9 /L, p = 0.001) and B cells (median 3.12 � 10 9 /L vs. 0.68 � 10 9 /L, p < 0.001) counts at S2, absence of immunosuppressive drugs or chemotherapy (82% vs. 56%, This observational study demonstrates a long-term high protection of Allo-HSCT recipients vaccinated three times with the BNT162b2 anti-SARS-CoV-2 mRNA vaccine. The median delay of 44 days after the second shot could be reconsidered as a longer interval between the second priming dose of vaccine and the booster dose appears to result in higher neutralizing antibody titers against all variants tested in a recent study. 4 Waning of IgG titers concerns around 30% of our patients at 6 months but only a small proportion (19%) had IgG titers <250 BAU/ml, suggesting the possibility to propose a fourth injection to enhance protection in these cases. Of note, in healthy population, a 6-month long-term follow-up after the booster have been reported showing that neutralization titers against the omicron variant were 6.3 times lower than the peak titers assessed 1 month after the booster injection, but the titers remained detectable in all the participants. 5 T-cell immunity may be also interesting to investigate at distance of the boost but this is currently challenging and not performed in routine practice. Finally, although the Delta variant was predominant during the period of our analyses, the lesser gravity of Omicron suggests that the same results should be observed, although this hypothesis has to be confirmed in the next few months. Using the same serologic assays at S1 and S2 for comparison. The authors declare no conflict of interest. All procedures followed were in accordance with the ethical stan- Email: patrice.chevallier@chu-nantes.fr The principal investigator PC had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Patrice Chevallier https://orcid.org/0000-0003-3142-5581 Pierre Peterlin https://orcid.org/0000-0001-5463-6686 Marie C. Béné https://orcid.org/0000-0002-6569-7414 The peer review history for this article is available at https://publons. com/publon/10.1002/hon.3006. Immune responses to two and three doses of the BNT162b2 mRNA vaccine in adults with solid tumors Antibody response after 2 and 3 doses of SARS-CoV-2 mRNA vaccine in allogeneic hematopoietic cell transplant recipients. Blood. 2021: blood A portrait of SARS-CoV-2 infection in patients undergoing hematopoietic cell transplantation: a systematic review of the literature Effects of a prolonged booster interval on neutralization of omicron variant SARS-CoV-2 omicron variant neutralization after mRNA-1273 booster vaccination