Azithromycin distribution and childhood mortality in compliance-related subgroups in Niger: complier average causal effect and spillovers in a cluster-randomized, placebo-controlled trial

Extension of efficacy range for targeted malaria-elimination interventions due to spillover effects

Malaria-elimination interventions aim to extinguish hotspots and prevent transmission to nearby areas. Here, we re-analyzed a cluster-randomized trial of reactive, focal interventions (chemoprevention using artemether-lumefantrine and/or indoor residual spraying with pirimiphos-methyl) delivered within 500 m of confirmed malaria index cases in Namibia to measure direct effects (among intervention recipients within 500 m) and spillover effects (among non-intervention recipients within 3 km) on incidence, prevalence and seroprevalence. There was no or weak evidence of direct effects, but the sample size of intervention recipients was small, limiting statistical power. There was the strongest evidence of spillover effects of combined chemoprevention and indoor residual spraying. Among non-recipients within 1 km of index cases, the combined intervention reduced malaria incidence by 43% (95% confidence interval, 20-59%). In analyses among non-recipients within 3 km of interventions, the combined intervention reduced infection prevalence by 79% (6-95%) and seroprevalence, which captures recent infections and has higher statistical power, by 34% (20-45%). Accounting for spillover effects increased the cost-effectiveness of the combined intervention by 42%. Targeting hotspots with combined chemoprevention and vector-control interventions can indirectly benefit non-recipients up to 3 km away.

Indirect (herd) effects of topical antibiotic prophylaxis and oral care versus non-antimicrobial methods increase mortality among ICU patients: realigning Cochrane review data to emulate a three-tier cluster randomised trial

OBJECTIVE

This study aimed to estimate the direct effects to recipients and indirect (herd) effects to non-recipients of each of topical antibiotic prophylaxis (TAP) and oral care methods on patient mortality within randomised concurrent controlled trials (RCCT) using Cochrane review data.

DESIGN

Control and intervention groups from 209 RCCTs of TAP (tier 3), oral care (tier 2) each versus non-antimicrobial (tier 1) ventilator-associated pneumonia (VAP) prevention interventions arranged to emulate a three-tiered cluster randomised trial (CRT). Eligible RCCTs were those including ICU patients with >50% of patients receiving >24 hours of mechanical ventilation (MV) with mortality data available as abstracted in 13 Cochrane reviews.

EXPOSURES

Direct and indirect exposures to either TAP or oral care within RCCTs versus non-antimicrobial VAP prevention interventions.

MAIN OUTCOMES AND MEASURES

The ICU mortality within control and intervention groups, respectively, within RCCTs of either TAP or oral care versus that within non-antimicrobial VAP prevention RCCTs serving as benchmark.

RESULTS

The ICU mortality was 23.9%, 23.0% and 20.3% for intervention groups and 28.7%, 25.5% and 19.5% for control groups of RCCTs of TAP (tier 1), oral care (tier 2) and non-antimicrobial (tier 3) methods of VAP prevention, respectively. In a random effects meta-regression including late mortality data and adjusting for group mean age, year of study publication and MV proportion, the direct effect of TAP and oral care versus non-antimicrobial methods were 1.04 (95% CI 0.78 to 1.30) and 1.1 (95% CI 0.77 to 1.43) whereas the indirect effects were 1.39 (95% CI 1.03 to 1.74) and 1.26 (95% CI 0.89 to 1.62), respectively.

CONCLUSIONS

Indirect (herd) effects from TAP and oral care methods on mortality are stronger than the direct effects as made apparent by the three-tiered CRT. These indirect effects, being harmful to concurrent control groups by increasing mortality, perversely inflate the appearance of benefit within RCCTs.

Targeted malaria elimination interventions reduce Plasmodium falciparum infections up to 3 kilometers away

Malaria elimination interventions in low-transmission settings aim to extinguish hot spots and prevent transmission to nearby areas. In malaria elimination settings, the World Health Organization recommends reactive, focal interventions targeted to the area near malaria cases shortly after they are detected. A key question is whether these interventions reduce transmission to nearby uninfected or asymptomatic individuals who did not receive interventions. Here, we measured direct effects (among intervention recipients) and spillover effects (among non-recipients) of reactive, focal interventions delivered within 500m of confirmed malaria index cases in a cluster-randomized trial in Namibia. The trial delivered malaria chemoprevention (artemether lumefantrine) and vector control (indoor residual spraying with Actellic) separately and in combination using a factorial design. We compared incidence, infection prevalence, and seroprevalence between study arms among intervention recipients (direct effects) and non-recipients (spillover effects) up to 3 km away from index cases. We calculated incremental cost-effectiveness ratios accounting for spillover effects. The combined chemoprevention and vector control intervention produced direct effects and spillover effects. In the primary analysis among non-recipients within 1 km from index cases, the combined intervention reduced malaria incidence by 43% (95% CI 20%, 59%). In secondary analyses among non-recipients 500m-3 km from interventions, the combined intervention reduced infection by 79% (6%, 95%) and seroprevalence 34% (20%, 45%). Accounting for spillover effects increased the cost-effectiveness of the combined intervention by 37%. Our findings provide the first evidence that targeting hot spots with combined chemoprevention and vector control interventions can indirectly benefit non-recipients up to 3 km away.

Establishing the safety of selective digestive decontamination within the ICU population: a bridge too far?

BACKGROUND

Infection prevention interventions within the intensive care unit (ICU) setting, whether studied within quality improvement projects or cluster randomized trials (CRT), are seen as low risk and grounded in an ethical imperative. Selective digestive decontamination (SDD) appears highly effective at preventing ICU infections within randomized concurrent control trials (RCCTs) prompting mega-CRTs with mortality as the primary endpoint.

FINDINGS

Surprisingly, the summary results of RCCTs versus CRTs differ strikingly, being respectively, a 15-percentage-point versus a zero-percentage-point ICU mortality difference between control versus SDD intervention groups. Multiple other discrepancies are equally puzzling and contrary to both prior expectations and the experience within population-based studies of infection prevention interventions using vaccines. Could spillover effects from SDD conflate the RCCT control group event rate differences and represent population harm? Evidence that SDD is fundamentally safe to concurrent non-recipients in ICU populations is absent. A postulated CRT to realize this, the SDD Herd Effects Estimation Trial (SHEET), would require > 100 ICUs to achieve sufficient statistical power to find a two-percentage-point mortality spillover effect. Moreover, as a potentially harmful population-based intervention, SHEET would pose novel and insurmountable ethical issues including who is the research subject; whether informed consent is required and from whom; whether there is equipoise; the benefit versus the risk; considerations of vulnerable groups; and who should be the gatekeeper?

CONCLUSION

The basis for the mortality difference between control and intervention groups of SDD studies remains unclear. Several paradoxical results are consistent with a spillover effect that would conflate the inference of benefit originating from RCCTs. Moreover, this spillover effect would constitute to herd peril.