The Effectiveness of Bivalent mRNA Omicron Containing Booster Vaccines Among Patients With Hematological Neoplasms

Background/Aim: Last year was characterized by the appearance of novel SARS-CoV-2 virus variants, mainly the omicron sub-lineages BA.2.12.1, BA.4, and BA.5, which have confirmed resistance to the acquired immune response developed following first-generation mRNA vaccines. Given the ability to use mRNA technology to respond quickly to variant strains, novel bivalent vaccines against novel omicron variants were generated. In the current work, we evaluated the efficacy and safety of novel bivalent mRNA Omicroncontaining booster vaccines among patients with hematological neoplasms, including both lymphoproliferative and myeloid malignancies. Patients and Methods: Cohort patients were obtained from electronic medical records of Maccabi Healthcare Services (MHS), the second-largest healthcare organization in Israel. We analyzed the outcome of all patients with hematological neoplasms, between September 21, 2022, and December 31, 2022, who were identified as having SARS-CoV-2 infection based on polymerase chain reaction (PCR) tests. The Kaplan-Meier method was used to compare the proportion of patients hospitalized for SARSCoV- 2 infection within 30 days among recipients and nonrecipients of omicron vaccine. Results: During the study period, 472 patients were infected with Omicron. We compared the outcome of 70 patients who received the bivalent mRNA booster to 402 who did not. Fewer bivalent recipients needed COVID-19-related hospitalization [2 of 70 (2.9%)] in comparison to the non-vaccinated cohort [42 of 402 (10.4%)] (p-value=0.0304). This represents an 89% relative risk reduction in COVID-19-related hospitalization in patients with hematological neoplasms. The median duration of hospitalization was 7 days for the non-vaccinated group and 4 for the vaccinated group. A statistically significant increase in ischemic stroke rates due to bivalent mRNA Omicron-containing booster vaccine was not observed. Conclusion: The bivalent Omicron-containing vaccine mRNA booster has a protective effect in preventing and shortening hospitalization in patients with hematological neoplasms with an acceptable safety profile.