High concentrations of ivermectin demonstrated antiviral activity against SARS-CoV-2 in vitro . Aim of this study was to assess safety and efficacy of high-dose ivermectin in reducing viral load in individuals with early SARS-CoV-2 infection. Randomised, double-blind, multicentre, phase II, dose-finding, proof-of-concept clinical trial. Participants: adults recently diagnosed with asymptomatic/oligosymptomatic SARS-CoV-2 infection, providing informed consent. Exclusion criteria: pregnant or lactating women; CNS diseases; dialysis; severe medical condition with prognosis < 6 months; warfarin treatment; antiviral/chloroquine phosphate/hydroxychloroquine treatment. Participants were assigned according to a randomized permuted block procedure to one of the following arms with allocation ratio 1:1:1: placebo (arm A); single dose ivermectin 600 μg/kg plus placebo for 5 days (arm B); single dose ivermectin 1200 μg/kg for 5 days (arm C). Primary outcomes: serious adverse drug reactions (SADR) and change of viral load at Day 7. From 31 th July, 2020 to 26 th May, 2021, 32 participants were randomized to arm A, 29 to arm B and 32 to arm C. The recruitment was stopped on 10 th June, because of a dramatic drop of cases. Eighty-nine participants were included in the safety analysis set, the change in viral load was calculated on 87 participants. No SADR were registered. The mean log10 viral load reduction was 2.9 in arm C (SD 1.6), 2.5 (2.2) in arm B and 2.0 (2.1) in arm A, with no significant differences (p=0.099 and 0.122 for C versus A and B versus A, respectively). High-dose ivermectin was safe, but did not prove efficacy to reduce viral load.

SARS-CoV-2 infection was monitored in 1898 health care workers (HCWs) after receiving full vaccination with BNT162b2. Untill 30 June 2021, 10 HCWs tested positive for SARS-CoV-2 using real time RT-PCR, resulting in a 4-month cumulative incidence of 0.005%. The infection was mildly symptomatic in six (60%) and asymptomatic in four (40%) individuals. Among the infected HCWs, eight consenting individuals provided paired NPS and saliva during the course of infection, for the purpose of the analysis performed in the present study. Genomic and subgenomic viral RNAs were investigated using real-time RT-PCR in both biological specimens. The temporal profile of viral load was measured using ddPCR. Viral mutations were also analysed. Subgenomic viral RNA was detected in 8/8 (100%) NPS and in 6/8 (75%) saliva specimens at the baseline. The expression of subgenomic RNA was observed for up to 7 days in 3/8 (38%) symptomatic cases. Moreover, concordance was observed between NPS and saliva in the detection of viral mutations, and both N501Y and 69/70del (associated with the B.1.1.7 variant) were detected in the majority 6/8 (75%) of subjects, while the K417T mutation (associated with the P.1-type variants) was detected in 2/8 (25%) individuals. Overall, our findings report a low frequency of infected HCWs after full vaccination. It is, therefore, important to monitor the vaccinees in order to identify asymptomatic infected individuals. Saliva can be a surrogate for SARS-CoV-2 surveillance, particularly in social settings such as hospitals.

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