The year-long coronavirus pandemic has had a significant impact on the nation’s blood supply as blood drives have been canceled and facilities used as collection centers were forced to shut their doors.

But with safety measures now in place to help protect donors from the virus, organizations such as the Red Cross are accepting — even urging — donations by appointment.

Still, in this new era, those who have had the virus or have been vaccinated against it may wonder whether they are eligible to give or whether it’s in their best interest to do so.

In most cases, the answer is yes. Here’s what we know about donating blood if you’ve had the coronavirus or have been vaccinated.

If I’ve had covid-19 or taken a coronavirus vaccine, can I still donate blood?

Of course — but with stipulations.

Although certain blood donation centers may have their own rules, at the Red Cross, donors who have been diagnosed with covid-19, the disease the virus causes; tested positive for the virus; or experienced any recent symptoms can still donate blood, but they must wait at least 14 days. Because some centers require longer deferrals, check with local blood banks.

For donors who have recently been vaccinated against the virus, there is not typically a need to wait unless a donor is having symptoms after vaccination, according to Red Cross guidelines. You don’t need to wait to donate blood after being vaccinated with any of the FDA-approved versions (Pfizer, Moderna, Johnson & Johnson).

Only individuals who have taken a live attenuated coronavirus vaccine are asked hold off on donation for a period of two weeks. But that is an unlikely scenario in the United States because such coronavirus vaccines have not been approved for use here.

All of this being said, anyone who has received an experimental vaccine as part of a clinical trial may be asked to delay.

Those who have been vaccinated can also donate platelets and AB Elite plasma to the Red Cross, but the organization is not accepting convalescent plasma from people who have taken a vaccine.

Does blood donation after vaccination reduce my protection?

No.

When someone has had the coronavirus or has received a vaccine to protect against it, the body’s immune system produces antibodies and protective T cells, a white blood cell that helps protect against the disease.

Yes, those immune responses are stored throughout the body. But the amount that would be taken during blood donation would not be enough to matter, said Rob Murphy, an infectious-disease expert at Northwestern University.

Average adults have about 10 pints of blood in their bodies, and whole blood donation requires only about 1 pint. The amount of coronavirus antibodies in that amount of blood would be negligible at best, not to mention the fact that the human body is constantly producing more blood, Murphy said.

Unlike with some disease, coronavirus immunity does wane over time, but routine blood donation would not factor into that.

Can you gain immunity by getting blood from a vaccinated donor?

Not enough to make a difference.

Even with a blood transfusion, there would be a relatively small amount of coronavirus antibodies in the donor’s blood, Murphy said. That goes for donors who were vaccinated or donors who have recovered from a coronavirus infection.

“You’ll get their antibodies, but it’s not enough to make any kind of impact,” he explained.

Medical professionals have tried convalescent plasma therapy — taking plasma loaded with coronavirus antibodies from people who have recovered from covid-19 and giving it to patients who are fighting the disease. The Food and Drug Administration authorized the treatment for emergency use last year.

However, two large studies out of Canada and the United Kingdom recently showed that most covid-19 patients who were treated with convalescent plasma in the hospital did not fare much better than those who didn’t. And a recent analysis of four clinical trials showed similar results.

Murphy said a much better alternative has been laboratory-designed monoclonal antibodies, which are made by Regeneron Pharmaceuticals and Eli Lilly. The key is to give the infusions early in the course of the disease, even prophylactically, but that can be a challenge because many hospitals do not offer it or have strict guidelines on which patients can qualify for it, he added.

As for blood donation, Murphy said it has such a small impact on gaining or losing immunity that “it’s just not an issue.”

“The vaccine does not limit your ability to donate blood, and they’re always short on donors, so please do it,” he said.

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