Are there double-blind Randomized Controlled Trials (RCTs) for vaccine efficacy?

From the Guidelines

Yes, there are double-blind Randomized Controlled Trials (RCTs) for vaccine efficacy, as evidenced by the Oxford-AstraZeneca vaccine trial, which included a double-blind design with a 1:1 ratio of vaccine to placebo 28 days apart, demonstrating a vaccine efficacy of 90.0% (67.4-97.0) for 0.5 and full dose vs 5.0 [95% CI, 1.2-7.7] 1.

Key Points

• The Oxford-AstraZeneca vaccine trial used a single-blind and double-blind design to evaluate vaccine efficacy against COVID-19 1.
• The primary outcome of the trial was efficacy against COVID-19, with secondary outcomes including efficacy after both doses and safety or side effects 1.
• The results of the trial showed a vaccine efficacy of 90.0% (67.4-97.0) for 0.5 and full dose vs 5.0 [95% CI, 1.2-7.7] 1.
• The AstraZeneca vaccine also underwent a multicenter, international RCT, which demonstrated an efficacy of 62.1% (95% CI, 41.0-75.7) after the first dose 1.

Study Design and Outcomes

The Oxford-AstraZeneca vaccine trial used a double-blind design, which is considered the gold standard for evaluating vaccine safety and efficacy. The trial included a large number of participants and measured outcomes such as infection rates, symptom severity, and adverse events between the vaccine and placebo groups. The results of the trial provide strong evidence for the efficacy of the Oxford-AstraZeneca vaccine against COVID-19.

Clinical Implications

The findings of the Oxford-AstraZeneca vaccine trial have important implications for clinical practice. The high efficacy of the vaccine against COVID-19 suggests that it can be an effective tool for preventing infection and reducing the risk of severe disease. The results of the trial also highlight the importance of using a double-blind design in vaccine trials to minimize bias and ensure accurate assessment of vaccine efficacy. Overall, the evidence from the Oxford-AstraZeneca vaccine trial supports the use of double-blind RCTs for evaluating vaccine efficacy and demonstrates the importance of rigorous clinical trials in establishing the safety and efficacy of vaccines 1.

From the Research

Double-Blind Randomized Controlled Trials (RCTs) for Vaccine Efficacy

• There are several double-blind RCTs that have been conducted to evaluate the efficacy of various COVID-19 vaccines, including:
  • A phase 1/2 clinical trial of an inactivated SARS-CoV-2 vaccine (CoronaVac) in healthy adults aged 18-59 years 2
  • A phase 1 trial of a recombinant receptor-binding domain-based protein subunit vaccine (Noora vaccine) against COVID-19 in adults 3
  • A phase I and phase II studies of a recombinant two-component SARS-CoV-2 protein vaccine (ReCOV) in healthy adults 4
  • A multicenter, randomized, double-blind, placebo-controlled phase III clinical trial of CoronaVac in children and adolescents aged 6 months to 17 years 5
• These studies have demonstrated the safety and immunogenicity of the vaccines, with significant seroconversion rates and neutralizing antibody responses observed in the vaccine groups compared to the placebo groups
• The results of these studies support the use of these vaccines in preventing COVID-19 and highlight the importance of continued research and development of effective vaccines against emerging variants

Key Findings

• The phase 1/2 trial of CoronaVac found that the vaccine was safe and immunogenic, with a seroconversion rate of 92% in the 3 μg group and 98% in the 6 μg group 2
• The phase 1 trial of Noora vaccine found that the vaccine was safe and immunogenic, with a seroconversion rate of 80% and a neutralizing antibody response of 100% 3
• The phase I and phase II studies of ReCOV found that the vaccine was safe and immunogenic, with a neutralizing antibody response against the prototype and several SARS-CoV-2 variants 4
• The phase III trial of CoronaVac in children and adolescents found that the vaccine was safe and immunogenic, with a vaccine efficacy of 21.02% and a significant increase in neutralizing antibody levels compared to the placebo group 5

Study Designs

• The studies used a randomized, double-blind, placebo-controlled design to evaluate the safety and efficacy of the vaccines
• The participants were randomly assigned to receive the vaccine or a placebo, and the outcomes were measured at various time points after vaccination
• The use of a placebo control group allowed for the comparison of the vaccine groups to a control group, providing a more accurate assessment of the vaccine's efficacy and safety 6