When SARS‑CoV‑2 hit, scientists leveraged decades of coronavirus research to sprint from gene sequence to human trials. Prior work on SARS and MERS had already identified the spike protein as the prime antigen, and structural biology tools clarified its pre‑fusion shape. That groundwork let companies like Pfizer design a vaccine in two days and move quickly to animal testing.

The breakthrough hinged on stabilizing the spike in its pre‑fusion configuration, which mimics the form the immune system first sees. Cryo‑EM advances revealed this shape, and a handful of mutations locked it in place. Vaccines that incorporated the pre‑fusion spike—notably the mRNA platforms and Novavax—generated far stronger neutralizing antibodies than those that did not.

Regulatory speed came from overlapping trial phases and massive enrollment. Pfizer and Moderna combined phases 2 and 3, completing a 4.5‑month efficacy study that usually spans years. Their trials recruited 30,000 participants each, a scale made possible by heightened public willingness and streamlined recruitment networks. The result was a set of safe, effective vaccines delivered within a year of the pandemic’s start.