evidence: The Link Between J&J’s COVID Vaccine and Blood Clots: What You Need to Know [Originally published: April 21, 2021. Updated: May 17, 2023.] [...] In May 2023, existing doses of the J&J vaccine expired and the Centers for Disease Control & Prevention (CDC) directed providers to dispose of any that had gone unused. This article is no longer up to date. Read our primer on COVID vaccines for more information. [...] Both the AstraZeneca and Johnson & Johnson vaccines, as well as the Sputnik V vaccine in Russia (also not approved for use in the U.S.) are carrier—or vector—vaccines, which instruct human cells to make the SARS CoV-2 spike protein. For this vaccine technology, scientists engineer a harmless inactivated common adenovirus (which can cause colds and other illnesses when it is active) into a sort of Trojan Horse that carries genetic code to a vaccine recipient’s cells. The code then instructs the cells to produce a spike protein that trains the body’s immune system, which then creates antibodies and memory cells to protect against an actual SARS-CoV-2 infection.