Since the beginning of the pandemic, public health authorities have provided support to long-term care facilities (LTCFs) for the implementation of risk mitigation measures. Nevertheless, the necessity of these measures has been doubted, especially after vaccines and antiviral treatment became available. Here, we present the burden of COVID-19 infection in LTCFs during the first 9 months of 2022 across Greece. We tested the possible association of LTCF characteristics and public health response with the occurrence of clusters (two or more linked cases in LTCFs) with facilities recording one case as reference. After excluding LTCFs with sporadic cases, we tested the effect of the abovementioned variables on attack rate (cases/total number of persons in the LTCF). The disease burden in LTCFs was high and substantially varied among facilities, with hospitalization and case fatality rates ranging from 2 to 80% (median 14%, IQR 27%) and from 1 to 50% (median 5%, IQR 7%), respectively. The probability of transmission inside the facility increased when notification of public health authorities was delayed (p-value < 0.001) after adjusting for vaccination status and phase of the pandemic. Results showed that active support from public health authorities is still important in reducing the burden in LTCFs.