Study population and setting
This study quantified interruptions to malaria preventive services due to COVID-19, and the potential impact of these interruptions on malaria morbidity and mortality in Nigeria and across sub-Saharan Africa (SSA). COVID-19 trajectories were constructed using a previously developed age-structured Susceptible-Exposed-Infectious-Susceptible model. Malaria deaths were estimated using a previously published malaria transmission dynamics model. Assuming an R0 (basic reproductive number) of 3, authors assessed the four COVID-19 transmission scenarios: 1. unmitigated (no direct action, but contact rates reduced by 20%); 2. mitigation (isolation and social distancing reduced contact rates by 45% for 6 months); 3. indefinite suppression (strict interventions reduce contact rates by 75% and are maintained indefinitely); and 4. suppression lift (strict interventions reduce contact rates by 75%, but these are only maintained for 2 months, after which time contact rates return to 80%). Authors included varying combinations of interruptions to the following malaria prevention activities: 1. distribution of long-lasting insecticide-treated nets (LLIN) would be delayed for a year or continue as normal, 2. seasonal malaria chemoprevention (SMC) would be interrupted, reduced, or continue as normal, and 3. clinical treatments would be interrupted, reduced, or continue as normal. Using Nigeria as an example, authors also estimated how changes to R0 (reproductive number) of COVID-19 could impact malaria deaths and the effect of broadening target ages for SMC.
Summary of Main Findings
If SMC coverage and case treatment were reduced by 50%, malaria deaths were estimated to increase by 42,000 (95% Uncertainty Interval: 22,000-62,000) in Nigeria and by 200,000 (95% UI: 115,000-285,000) across SSA, even if LLIN campaigns were not interrupted. However, if LLIN campaigns were also interrupted in addition to SMC and treatment reductions, excess malaria mortality was estimated to be as high as 495,000 (95% UI: 296,000-693,000) across SSA. If LLIN campaigns, SMC coverage, and treatment were all interrupted, malaria deaths were estimated to increase across SSA by as much as 696,000 (95% UI: 413,000-978,000). If R0 was 2.5 compared to 3.0, authors estimated the epidemic in Nigeria would increase from 6 to 9 months, thereby increasing malaria deaths by approximately 17%, even if LLIN campaigns continued and some case treatment was maintained. In scenarios where LLIN campaigns were interrupted, increasing the target age for SMC from <5 years to <15 years was estimated to save 22,500 lives in Nigeria.
Authors conducted sensitivity analyses to account for uncertainty in the models.
Overall, results are subject to several sources of uncertainty, the foremost being that it is unknown how COVID-19 will spread across SSA. Countries will likely experience varying levels of transmission and respond with different combinations of mitigation strategies, both of which will affect the degree to which malaria activities are disrupted. Parameters included in the COVID-19 model are based on data from the United Kingdom and China, which may not be appropriate for SSA. Authors used Nigeria as a case example for some estimates, but even these results should not be generalized to other parts of SSA.The model assumed that the impact of COVID-19 on malaria deaths was determined solely by the duration of malaria service interruptions. However, duration is unlikely to be the only contributing factor to the effects of service interruptions on malaria-associated deaths; other factors, such as to what degree services are interrupted (i.e., intensity of interruptions), also likely play a role. It is not clear to what extent routine malaria services have truly been disrupted.
Dual epidemics of COVID-19 and malaria could quickly overwhelm already vulnerable health systems in sub-Saharan Africa. This study contributes to the growing body of literature estimating the potential indirect effects of COVID-19 in Africa, and illustrates the need to prioritize malaria prevention methods such as routine distribution of long-lasting insecticide-treated nets.
This review was posted on: 22 September 2020