Risk of SARS-CoV-2 infection in patients with hematologic diseases receiving tixagevimab/cilgavimab as pre-exposure prophylaxis in most recent Omicron sublineages era.

INTRODUCTION: Whether pre-exposure prophylaxis (PrEP) with tixagevimab/cilgavimab 150mg/150 mg (T/C) in individuals with hematological diseases (HD) may lead to a reduced risk of Breakthrough SARS CoV2 infection/hospitalization or death in the Omicron era remains to be established.

METHODS: Observational study including participants with HD who received PrEP. breakthrough infections were defined as a SARS-CoV-2 positivity by RT-PCR. The incidence of breakthrough infections (95%CI) and of breakthrough infections /hospitalization/death was calculated using the Kaplan-Meier method and as the number of breakthrough infections per 100-PYFU according to the circulating variant (VoC). A Poisson regression model was used to evaluate the association between the rate of incidence and circulating VoCs after controlling for demographics and clinical factors.

RESULTS: We included 550 HD patients: 71% initiated T/C PrEP when BA.5 was the most prevalent, followed by XBB/EG, BA.2 and BA.1 (19%, 7% and 3%, respectively). Overall, the 1-year incidence estimate of breakthrough infections/hospitalization/death was 24% (18.7-29.4%). A greater risk of incident infections was observed when BA.5 and XBB/EG sub-lineages circulated [aRR 5.05 (2.17, 11.77); p<.001 and 3.82 (1.50, 9.72); p=0.005, compared to BA.1, respectively].

CONCLUSIONS: The one-year incidence of SARS-CoV-2 breakthrough infections/hospitalization/death was 24% which is in line with what observed in other similar studies. The risk appeared to be higher when more recent Omicron sub-lineages were circulating suggesting a reduction of in vitro neutralization.