Study summary
Topical repellents for malaria prevention (Cochrane systematic review)
Gabaldón-Figueira JC, Wagah MG, Maia MF, et al.
Read the original paper- Study type
- Meta Analysis
- Year
- 2023
- Published in
- Cochrane Database of Systematic Reviews 2023, Art. No. CD015422
- Evidence strength
- Definitive evidence
How it was tested
Cochrane systematic review and meta-analysis of randomized trials testing whether topical repellents reduce malaria infection.
Summary
A Cochrane team pooled the trial evidence on whether skin-applied repellents actually cut malaria, not just bites. The question matters because bed nets and indoor spraying miss the outdoor, early-evening biting that a repellent could cover. They gathered eight randomized trials with more than 60,000 people, mostly in lower-transmission parts of Southeast Asia and South America.
Key findings
The honest headline is that topical repellents may slightly reduce Plasmodium falciparum malaria, but the evidence is weak and uneven. Combined infection and clinical-case incidence fell about a quarter (rate ratio 0.74, 95% confidence interval 0.56 to 0.98) and parasite prevalence dropped similarly (odds ratio 0.81, 0.67 to 0.97), both statistically significant. But infection incidence on its own (rate ratio 0.76, 0.56 to 1.02) and clinical cases on their own were not significant, and the certainty of evidence was rated low across the board. The apparent benefit came mostly from high-risk groups such as refugees with no bed nets; there was not enough evidence that repellents add protection where nets or indoor spraying are already in place. Adverse effects were limited to mild skin reactions in about 0.6% of users.
Limitations
Only eight trials, several underpowered, and much of the signal rode on a few high-risk populations, which limits how far the results generalize. Adherence was hard to pin down (self-reported 34 to 95%, observed 7.9 to 99.2%), and the low certainty reflects the risk of bias and indirectness the authors flag.