Prophylaxis study using ivermectin and carrageenan showing 0 of 788 cases from treated healthcare workers, compared to 237 of 407 control.
The effect is likely to be primarily due to ivermectin - the author has later reported that carrageenan is not necessary [1].
Carvallo et al., 11/17/2020, prospective, Argentina, South America, peer-reviewed, 4 authors, dosage 12mg weekly.
risk of COVID-19 case, 99.9% lower, RR 0.001, p < 0.001, treatment 0 of 788 (0.0%), control 237 of 407 (58.2%).
Effect extraction follows pre-specified rules prioritizing more serious
outcomes. For an individual study the most serious outcome may have a smaller
number of events and lower statistical signficance, however this provides the
strongest evidence for the most serious outcomes when combining the results of
many trials.