I read with interest the meta-analysis of zinc salts lozenges for treatment of the common cold by Jackson et al.1 Six of the 8 studies published were included in this meta-analysis. Two studies using viral inoculation of volunteers were excluded because of their different designs. The virus challenge model has certain advantages over the natural cold model, which makes it an acceptable method of investigating effectiveness of various remedies for the common cold.2 The authors assigned an odds ratio (OR) of 1.0 for these studies; using the duration of viral shedding as a surrogate marker for duration of symptoms, they produced a subsequent summary OR of 0.57 for the presence of any cold symptoms at 7 days. It is expected that viral shedding might persist after resolution of symptoms, so this OR is overestimated.
Mossad SB. Another Look at a Meta-analysis of Zinc Salts Lozenges and the Common Cold. Arch Intern Med. 1998;158(9):1038-1040. doi: