Figure 1.
Vaccine development against COVID-19; number of vaccines in pre-clinical and clinical phases, in phase I, phase I/II, phase II, phase II/III, and phase III.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.