Testing indoor residual spraying coverage targets for malaria control, Bioko, Equatorial Guinea

Area of Science:

• Public Health
• Infectious Disease Epidemiology
• Vector Control

Background:

• Indoor residual spraying (IRS) is a key malaria control strategy.
• Current IRS guidelines recommend 80% household coverage.
• Lower coverage may increase feasibility, cost-effectiveness, and equity.

Purpose of the Study:

• To evaluate the non-inferiority of 50% IRS coverage compared to 80% coverage for malaria control.
• To assess the impact of reduced IRS coverage on Plasmodium falciparum infection rates.

Main Methods:

• A cluster-randomized trial was conducted in Bioko, Equatorial Guinea (2021-2022).
• Two arms were established: 80% IRS coverage (control) and 50% IRS coverage (intervention).
• Malaria infection was assessed annually using rapid diagnostic tests; difference-in-differences analysis was employed.

Main Results:

• Post-intervention, odds of malaria infection were 0.97 (95% CI: 0.72-1.29) in the 50% arm and 1.11 (95% CI: 0.81-1.52) in the 80% arm.
• Adjusted analysis showed no significant difference in the change of P. falciparum infection odds between arms (OR: 0.89; 95% CI: 0.58-1.36).
• The upper bound of the confidence interval was below the non-inferiority margin of 1.43.

Conclusions:

• 50% IRS coverage demonstrated non-inferiority to 80% coverage in reducing malaria infection.
• Lower IRS coverage targets can be considered to enhance program feasibility, cost-effectiveness, and equity.
• Findings support adapting IRS coverage levels based on local operational contexts.