Estimating vaccine efficacy during open-label follow-up of COVID-19 vaccine trials based on population-level surveillance data.

While rapid development and roll out of COVID-19 vaccines is necessary in a pandemic, the process limits the ability of clinical trials to assess longer-term vaccine efficacy. We leveraged COVID-19 surveillance data in the U.S. to evaluate vaccine efficacy in U.S. Government-funded COVID-19 vaccine efficacy trials with a three-step estimation process. First, we used a compartmental epidemiological model informed by county-level surveillance data, a "population model", to estimate SARS-CoV-2 incidence among the unvaccinated. Second, a "cohort model" was used to adjust the population SARS-CoV-2 incidence to the vaccine trial cohort, taking into account individual participant characteristics and the difference between SARS-CoV-2 infection and COVID-19 disease. Third, we fit a regression model estimating the offset between the cohort-model-based COVID-19 incidence in the unvaccinated with the placebo-group COVID-19 incidence in the trial during blinded follow-up. Counterfactual placebo COVID-19 incidence was estimated during open-label follow-up by adjusting the cohort-model-based incidence rate by the estimated offset. Vaccine efficacy during open-label follow-up was estimated by contrasting the vaccine group COVID-19 incidence with the counterfactual placebo COVID-19 incidence. We documented good performance of the methodology in a simulation study. We also applied the methodology to estimate vaccine efficacy for the two-dose AZD1222 COVID-19 vaccine using data from the phase 3 U.S. trial (ClinicalTrials.gov # NCT04516746). We estimated AZD1222 vaccine efficacy of 59.1% (95% uncertainty interval (UI): 40.4%-74.3%) in April, 2021 (mean 106 days post-second dose), which reduced to 35.7% (95% UI: 15.0%-51.7%) in July, 2021 (mean 198 days post-second-dose). We developed and evaluated a methodology for estimating longer-term vaccine efficacy. This methodology could be applied to estimating counterfactual placebo incidence for future placebo-controlled vaccine efficacy trials of emerging pathogens with early termination of blinded follow-up, to active-controlled or uncontrolled COVID-19 vaccine efficacy trials, and to other clinical endpoints influenced by vaccination.

Projected impact of treatment intensification with statin, ezetimibe, and statin plus ezetimibe fixed-dose combination on MACE across six countries.

AIMS: The 2019 European Society of Cardiology/European Atherosclerosis Society (ESC/EAS) dyslipidaemia guidelines recommend achievement of low-density lipoprotein cholestrol (LDL-C) goals based on an individual's risk. We aimed to evaluate the impact of guideline adoption with statin, ezetimibe, and statin plus ezetimibe fixed-dose combination (FDC) on LDL-C goal achievement and incidence of major adverse cardiovascular events (MACE) across six countries. METHODS AND RESULTS: A simulation model with a five-year horizon (2020-2024) was developed based on Institute for Health Metrics and Evaluation Global Burden of Disease Study database with a business-as-usual (BAU) scenario representing status quo, intervention scenario-1 representing treatment with statin and ezetimibe as separate agents, and intervention scenario-2 representing treatment with statin or statin plus ezetimibe FDC. MACE was defined as the composite of myocardial infarction, ischaemic stroke, and cardiovascular death. The mean population LDL-C was reduced from 4.25 mmol/L in the BAU scenario, to 3.65 mmol/L and 3.59 mmol/L in intervention scenarios-1 and -2, respectively. Compared with BAU, intervention scenarios-1 and-2 resulted in relative reduction of MACE by 5.4% and 6.4% representing ∼3.7 and 4.4 million MACE averted, respectively, across six countries over 5 years. The absolute benefit in terms of MACE averted was highest for China, whereas France had highest relative reduction in MACE with both intervention scenarios compared with BAU. CONCLUSION: The 2019 ESC/EAS guideline-based treatment intensification with strategies based on statin, ezetimibe, and statin plus ezetimibe FDC is estimated to result in a substantial population-level benefit in terms of MACE averted compared with BAU.