@tracy_tysonmd: “Double-blind placebo-controlled” trials are often called the gold standard of research—but in vaccine science, the reality is more nuanced. For a brand-new vaccine, placebo-controlled trials are often used before approval to determine whether the vaccine prevents disease and to evaluate safety. However, once an effective vaccine already exists, continuing to withhold protection from participants may be unethical. Imagine designing a study today where half of children receive no measles vaccine during an active outbreak. Even if the study produced cleaner data, exposing participants to a preventable serious illness would violate fundamental research ethics. That’s why many vaccine studies after initial approval use: ✅ Active comparators (comparing a new vaccine to an existing vaccine) ✅ Large population-based studies ✅ Post-marketing safety surveillance involving millions of people ✅ Case-control and cohort studies These study designs may not be double-blind placebo-controlled, but they often provide information that randomized trials cannot—especially for detecting very rare side effects or evaluating real-world effectiveness. Good science isn’t about worshipping a single study design. It’s about using the most ethical and appropriate methods to answer a question while protecting human participants. The strongest conclusions come from the totality of evidence, not from any one study type alone. #evidencebasedmedicine #vaccineswork #scienceliteracy #publichealth #pediatrics

Tracy Tyson MD

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Friday 19 June 2026 16:49:21 GMT