RESUMEN
BACKGROUND: Since the declaration of a new variant of concern (VOC), Omicron, by the World Health Organization in November 2021, a quick spread has been documented worldwide, being the main VOC in the sixth wave in Spain. The Omicron variant has more transmissibility, lower virulence, and less risk of severe disease than previously described VOC. Here we analyze the current wave of severe acute respiratory syndrome coronavirus 2 infection in liver transplant recipients (LTRs). METHODS: A retrospective observational study of 355 LTRs was conducted in La Rioja and Cantabria regions of Spain. Epidemiological and clinical parameters were gathered on the basis of clinical records and telephone interviews. RESULTS: In the current wave of infection, a higher number of LTRs have been found to be infected than the sum of the previous 5 waves (30 versus 16 LTRs). Of the 30 infected LTRs, 29 (96.6%) had received 3 vaccine doses (mRNA based), in a median of 93 d (interquartile range, 86-108) before infection. Eight of 30 LTRs (24.0%) were asymptomatic and 21 LTRs (67.8%) were with mild symptoms with a mean duration of 4.6 d (interquartile range, 2.5-7), whereas in the unvaccinated LTRs, the symptoms were fever, nausea, vomiting, and diarrhea. Moreover, in the sixth wave, intrafamiliar transmission was the main route of infection (17/30; 56.6%), and nosocomial transmission was confirmed in 2 LTRs (6.6%). CONCLUSIONS: In our series, increased transmissibility of the Omicron variant was confirmed, including nosocomial infection, with a lower risk of severe disease in LTRs. These findings could be supported by the universal vaccination of LTRs and less virulence of the Omicron variant.