Why getting a COVID-19 vaccine shouldn’t stop you from donating blood

You may be aware that there’s no deferral for blood donors after they receive a vaccine against COVID-19. But you might be wondering how the blood operators made this decision. Canadian Blood Services' medical director for donor and clinical services, Dr. Mindy Goldman, answers questions.

When people have recently received certain vaccines, they may have a waiting period, called a temporary deferral, before they can donate blood or plasma. So, as the global rollout of vaccines against COVID-19 began in December 2020, blood operators and their regulators needed to determine whether people who receive these vaccines should be temporarily deferred. This important question has implications for the safety of recipients and the sufficiency of the blood supply, given the hope that all Canadians who wish to be vaccinated will be by Fall 2021.

What are vaccines?

Vaccines are given to stimulate immunity against one or more diseases. Vaccines are made from the agent that causes the disease, or a natural or synthetic substance related to it, but they don’t cause the disease. Instead, vaccines stimulate the production of antibodies so that the recipient should have immunity if they are exposed to the disease in the future.

There are many different types of vaccine. Classical vaccines include live-attenuated vaccines and vaccines made from inactivated or weakened viruses, or those made from virus protein subunits or virus-like particles. Most vaccines that are licensed for use are made using these classical approaches, including MMR, polio and seasonal flu vaccines.

Advances in understanding of immunity and in biotechnology have led to newer approaches to making vaccines using what are called “next generation” platforms. These include vaccines made using a virus’ nucleic acids (e.g. DNA, RNA) and viral vectors, which are virus-based tools that can deliver information to cells.

Why are donors temporarily deferred from donation after some vaccinations?

Donors are deferred after receiving vaccines made with live attenuated viruses or bacteria due to concerns for the safety of blood recipients. Shortly after vaccination, blood may contain an infective agent which is not harmful to the donor but poses a theoretical risk of causing illness if transfused to a patient who is immunosuppressed.

Certain vaccinations have also been shown to interfere with transmissible disease testing that is conducted on all donations, causing “false positive” results. Donors are deferred if they’ve recently received these vaccines.

Many vaccinations cause no safety risk to recipients, and donors can donate after recent vaccination, provided they feel well.

So, what type of COVID-19 vaccines are in use in Canada?

Canada has secured accessed to vaccines from several leading companies, including Pfizer/BioNTech, Moderna, Jannsen and Novavax. None of these vaccines use live attenuated or weakened SARS-CoV-2 virus, so none should pose a safety risk to recipients. Many of the COVID-19 vaccines already in use, including the Pfizer-BioNTech Comirnaty® and Moderna Spikevax® vaccines, are next generation messenger (m)RNA vaccines, although some that may be available soon are being made using more classical approaches such as virus-like particles.

Tell me more about mRNA vaccines?

mRNA vaccines are very new! In fact, the first mRNA vaccines approved for use are those against COVID-19.

mRNA and other nucleic acid-based vaccines are produced using parts of the virus’ genetic material, rather than the virus itself or viral proteins. mRNA vaccines are often encased in a lipid membrane, which acts to protect the mRNA and ensure it can be taken up by cells. Once in a cell, the vaccine elicits an immune response against the virus. The amount of vaccine in the blood after receiving a vaccination of this type would likely be very low.

What type of evidence did you need to gather to determine whether donors should be deferred?

As with any important decision regarding blood donor deferrals, we gathered information on the types of vaccines that will be used in Canada and how these vaccines work. We considered the donor eligibility criteria implications for people receiving these vaccines, for whole blood, platelet and plasma donation as well as for COVID-19 convalescent plasma donation, including implications for patient safety and for sufficiency of supply. This process included understanding the known side effects of the vaccines to see if there were any that might be of concern to recipient safety. We also looked for information on whether any of these vaccines might interfere with the transmissible disease testing that blood operators do.

To do this work, we consulted with the vaccine manufacturers to better understand their products. We also consulted with colleagues at Héma-Québec and international colleagues, and reviewed the position of other regulatory authorities, such as the FDA in the US, to understand what deferrals are being implemented elsewhere and why.

A conference call was held with our regulator, Health Canada, and colleagues from Héma-Québec to ensure that everyone was in agreement with the policy being considered.

What did your investigation show?

As mentioned, none of the vaccines being used in Canada contain live attenuated virus or are likely to interfere with transmissible disease testing. While some of the vaccinations cause very rare serious side effects, none have demonstrated risk to transfusion recipients. Therefore, we advised that donors getting any of the already approved vaccines or other candidates planned for use in Canada should be eligible to donate. This advice is consistent with the approach being taking in the US, Australia and Germany. The UK and some European jurisdictions are applying temporary deferrals for some of the vaccines.

“You can do two great things on one day: boost your immunity to COVID-19, and if you feel well after your shot, boost Canada’s blood supply,” said Dr. Goldman.

What are the next steps?

As you know, COVID-19 vaccination is a fast-moving field! We will continue to monitor the situation as new vaccines enter the Canadian market and as the pandemic and our understanding of the virus and our immune response to it evolves.

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Through discovery, development and applied research, Canadian Blood Services drives world-class innovation in blood transfusion, cellular therapy and transplantation—bringing clarity and insight to an increasingly complex healthcare future. Our dedicated research team and extended network of partners engage in exploratory and applied research to create new knowledge, inform and enhance best practices, contribute to the development of new services and technologies, and build capacity through training and collaboration. Find out more about our research impact.