The world could witness another pandemic on the scale of COVID-19 in the future, prompting calls for research into how social and behavioral science can better contribute to pandemic response, especially regarding public engagement and communication. Here, we conduct a cost-effectiveness analysis of a familiar tool from social and behavioral science that could potentially increase the impact of public communication: survey experiments. Specifically, we analyze whether a public health campaign that pays for a survey experiment to pretest and choose between different messages for its public outreach has greater impact in expectation than an otherwise-identical campaign that does not. The main results of our analysis are 3-fold. First, we show that the benefit of such pretesting depends heavily on the values of several key parameters. Second, via simulations and an evidence review, we find that a campaign that allocates some of its budget to pretesting could plausibly increase its expected impact; that is, we estimate that pretesting is cost-effective. Third, we find pretesting has potentially powerful returns to scale; for well-resourced campaigns, we estimate pretesting is robustly cost-effective, a finding that emphasizes the benefit of public health campaigns sharing resources and findings. Our results suggest survey experiment pretesting could cost-effectively increase the impact of public health campaigns in a pandemic, have implications for practice, and establish a research agenda to advance knowledge in this space.