I wonder if patients will know if they receive the poisoned blood

From the Red Cross websire…

COVID-19 Vaccine and Blood Donor Eligibility Information

The Red Cross is following FDA blood donation eligibility guidance for those who receive a COVID-19 vaccination, and deferral times may vary depending on the type of vaccine an individual receives. If you’ve received a COVID-19 vaccine, you’ll need to provide the manufacturer name when you come to donate. Upon vaccination, you should receive a card or printout indicating what COVID-19 vaccine was received, and we encourage you to bring that card with you to your next donation. In most cases, there is no deferral time for individuals who received a COVID-19 vaccine as long as they are symptom free and feeling well at the time of donation. The following eligibility guidelines apply to each COVID-19 vaccine received, including boosters:

There is no deferral time for eligible blood donors who are vaccinated with an inactivated or RNA based COVID-19 vaccine manufactured by AstraZeneca, Janssen/J&J, Moderna, Novavax, or Pfizer. Eligible blood donors who received a live attenuated COVID-19 vaccine or do not know what type of COVID-19 vaccine they received must wait two weeks before giving blood. If you have an appointment scheduled and need to change your donation date based on the above guidance, click here. If you have further eligibility questions, please call 1-800-RED CROSS (1-800-733-2767).

https://www.redcrossblood.org/donate-blood/dlp/coronaviruscovid-19and-blood-donation.html