TCIM Research

Jennifer Hunter (2021-2022 WINNER)

Published on 10/2/2023

Zinc for the prevention or treatment of acute viral respiratory tract infections in adults: a rapid systematic review and meta-analysis of randomised controlled trials

Jennifer Hunter¹, Susan Arentz², Joshua Goldenberg³, Guoyan Yang⁴, Jennifer Beardsley⁴, Stephen P Myers^2,5, Dominik Mertz⁶, Stephen Leeder⁷

Affiliations:
¹ NICM Health Research Institute, Western Sydney University, Penrith, New South Wales, Australia Jennifer.Hunter@westernsydney.edu.au.
² NICM Health Research Institute, Western Sydney University, Penrith, New South Wales, Australia.
³ Helfgott Research Institute, National University of Natural Medicine, Portland, Oregon, USA.
⁴ Seattle, Washington, USA.
⁵ National Centre for Naturopathic Medicine, Southern Cross University, Lismore, New South Wales, Australia.
⁶ Division of Infectious Diseases, Department of Medicine, Health Sciences, McMaster University, Hamilton, Ontario, Canada.
⁷ The Menzies Centre for Health Policy, The University of Sydney, Sydney, New South Wales, Australia.

Abstract

Objective: To evaluate the benefits and risks of zinc formulations compared with controls for prevention or treatment of acute viral respiratory tract infections (RTIs) in adults.

Method: Seventeen English and Chinese databases were searched in April/May 2020 for randomised controlled trials (RCTs), and from April/May 2020 to August 2020 for SARS-CoV-2 RCTs. Cochrane rapid review methods were applied. Quality appraisals used the Risk of Bias 2.0 and Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

Results: Twenty-eight RCTs with 5446 participants were identified. None were specific to SARS-CoV-2. Compared with placebo, oral or intranasal zinc prevented 5 RTIs per 100 person-months (95% CI 1 to 8, numbers needed to treat (NNT)=20, moderate-certainty/quality). Sublingual zinc did not prevent clinical colds following human rhinovirus inoculations (relative risk, RR 0.96, 95% CI 0.77 to 1.21, moderate-certainty/quality). On average, symptoms resolved 2 days earlier with sublingual or intranasal zinc compared with placebo (95% CI 0.61 to 3.50, very low-certainty/quality) and 19 more adults per 100 were likely to remain symptomatic on day 7 without zinc (95% CI 2 to 38, NNT=5, low-certainty/quality). There were clinically significant reductions in day 3 symptom severity scores (mean difference, MD -1.20 points, 95% CI -0.66 to -1.74, low-certainty/quality), but not average daily symptom severity scores (standardised MD -0.15, 95% CI -0.43 to 0.13, low-certainty/quality). Non-serious adverse events (AEs) (eg, nausea, mouth/nasal irritation) were higher (RR 1.41, 95% CI 1.17 to 1.69, NNHarm=7, moderate-certainty/quality). Compared with active controls, there were no differences in illness duration or AEs (low-certainty/quality). No serious AEs were reported in the 25 RCTs that monitored them (low-certainty/quality).

Conclusions: In adult populations unlikely to be zinc deficient, there was some evidence suggesting zinc might prevent RTIs symptoms and shorten duration. Non-serious AEs may limit tolerability for some. The comparative efficacy/effectiveness of different zinc formulations and doses were unclear. The GRADE-certainty/quality of the evidence was limited by a high risk of bias, small sample sizes and/or heterogeneity. Further research, including SARS-CoV-2 clinical trials is warranted.

https://doi.org/10.1136/bmjopen-2020-047474

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