evidence: The mRNA (Moderna and Pfizer) vaccines do not contain live virus. Each of these contain a single gene from the virus that causes COVID-19. The gene instructs our cells to make the protein, but no other proteins from the virus are made, so whole virus particles are never present. In this manner, people who were vaccinated cannot shed, or spread, the virus to other people as a result of vaccination. If, however, the individual subsequently becomes infected, they can spread the virus during the days before and early during their infection. Of note, the amount of virus shed by vaccinated people quickly decreases, so they generally shed less virus overall compared to unvaccinated, infected individuals. This is also the case for the J&J/Janssen vaccine; however, that version is no longer available in the U.S. [...] Vaccinated people do not shed virus following vaccination. COVID-19 vaccines do not contain live viruses, nor do they cause production of whole viral particles. As such, there is no infectious virus to spread from a vaccinated person to someone else. [...] Giving blood after getting the COVID-19 vaccine will not diminish the resulting immune response, which mostly builds in the lymph nodes near the injection site. Likewise, the American Red Cross (ARC) does not require a delay following vaccination with the vaccines currently approved for use in the U.S.; however, individuals must know which brand of vaccine they received and show the immunization card if possible. More details about blood donation are available on the ARC website.