Ad26.COV2.S is a single-dose COVID-19 vaccine developedby by Johnson & Johnson. The US Food and Drug Administration (FDA) had recently found this vaccine to be safe for use. If FDA authorises it, this vaccine will be the third COVID-19 vaccine to be approved in the United States. The third phase of the vaccine trail is still underway. The vaccine uses genetic code to make spike protein, the protrusion seen on the surface of SARS-CoV-2.