This is not your father's gay blood ban era. We're overdue for a comprehensive reassessment

In June, Canadian Blood Services and Hma-Qubec will change their blood donor requirement for men who have had sex with other men (MSM), reducing the wait period to three months. At one time, these men weren't allowed to donate at all. That changed to a five-year deferral period in 2013, and a one-year deferral in 2016. All blood is tested. The rationale for MSM deferral relates to average risk of contact with HIV during the window period where someone newly infected may not test positive.

In Canada, blood products are regulated like drugs, meaning that despite our prime minister's 2015 campaign promise to end the ban, Health Canada ultimately has independent power. But even with assurances of evidence-based regulation, each incremental change has generated two responses. Some are convinced of increased risk to the blood supply with each reduction because in their minds, gay men = AIDS, while others decry the policy change as continuing discrimination against gay and bisexual men.

How do we make sense of this?

We can start by looking at the science in a systematic way. I'm an epidemiologist, and we analyze health risk statistics. The fact that you're still drinking a glass of wine each day because it's "good for your health?" That was us. Okay, maybe not our finest moment, but it just proves that people can ignore updated evidence to fit their rationalizations. Just like with wine, in a world of non-epidemiologists, we do a horrible job of understanding risk in a rational way.

The health of blood recipients depends on exactly this rationality. The ethics of inclusion and exclusion also depend on rational risk assessment.

Patchwork of deferrals

Discrimination to protect the health of blood recipients is fair only if it is based in legitimate protections, rather than biased assumptions. Our current policies are based on a patchwork of donor deferrals that have been implemented at different times in response to historic concerns. While updates may be based on evidence, that evidence itself may be limited, and the extent to which policies may still reflect a legacy of bias is unclear. At this point, a full evidence-based reassessment could ensure that policies are equitably tied to risk.

Conveniently, separating rational protections from non-rational assumptions is the key to both ethics and safety.

It is also the challenge that routinely turns blood donor policies into public relations nightmares. In Canada, we have the perfect storm to impede updates to blood policy. Its components? Historical context, inflated perception of risk, consideration of individual criteria in isolation, stigma, unclear necessity of discrimination and a non-transparent rationale that implies inconsistency. The first three feed the fearmongers, and the last three amplify equity concerns.

• Blood-donation deferral period drops to 3 months for gay, bisexual men

• Transgender man upset by blood agency's screening policy which considers him female

We find reason to fear in the gross negligence that let to the 1980s tainted blood scandal. To this we add our poor perception of risk, and with blood everything sounds risky. What if I told you we could probably safely stop screening donated blood for syphilis? Syphilis does not survive in refrigerated blood, and disappeared from transfusion transmission in Canada and the U.S. decades ago, yet we throw away non-infectious blood all the time as a result of this test.

This is a change worthy of evidence-weighing, but can you imagine the headlines?

Who will be newly eligible to donate in June? Well, a man who has not had sex with another man in the past three months and has never tested HIV-positive, injected drugs or done sex work, and in the last year has also not used cocaine, been in jail, been treated for syphilis or gonorrhea, or had sex with an HIV-positive partner or one who injects drugs, Of course he must also have avoided working with monkeys, getting a tattoo, and travelling to areas with malaria. The list goes on, but that already makes for a cumbersome headline.

So, will updating the MSM deferral to three months increase risk? It will not. Yes, as any internet commenter will tell you, MSM account for about half of the new HIV diagnoses for which we have risk data (such data are missing for 40 percent). Those who test HIV-positive, however, are not eligible to donate, and gay and bi men are more likely to be tested and therefore diagnosed than other groups.

As well, HIV-negative gay or bi men are increasingly using PrEP to prevent infection. More men living with HIV have undetectable viral loads, and U=U: undetectable really is untransmittable. In other words, this is not your gay father's blood ban era. Moreover, HIV has long since ceased to be the terminal illness it was more than two decades ago. Would I wish it on someone? No. Would I rather live my day-to-day life with HIV than type 1 diabetes? Absolutely. Does the continuing resistance to evidence-based policy change reflect homophobic assumptions rather than evidence? Yes, of course it does.

Effects of stigma

There is no legal right to give the gift of blood, but we value and expect equity. We are rightly concerned about the role of stigma. I shouldn't have to say this, but HIV is not spontaneously generated when two men touch each other. Stigma results in a strong linkage in some people's minds between sex between men and disease, and we may not even be able to conceptualize healthy, loving, joyful, life-affirming gay sex.

MSM are deferred for having sex with a potential partner group (other MSM) with higher-than-average risk of HIV. It is stigma that allows the continuation of this deferral while making new deferrals for elevated partner-group risk politically impossible. This and other apparent inconsistencies (e.g. deferral length) maintain perception of inequity. Rationale for behavioural deferrals needs to be as narrow as possible, consistent, and explicitly tied to specific purposes, such as preventing infections for which we have no test, versus preventing donations during the brief period where a high-quality tests may not yet detect a new infection (e.g., HIV, hepatitis B).

Does changing this policy reinforce ideals of equity? No, unfortunately it does not. However, both the fears of risk and the concerns for fairness can be addressed by the same solution: a transparent risk structure with a clear and equitable rationale for deferrals and testing.

Deferral criteria challenged by black and transgender communities (and partly addressed) can be incorporated, and new information supplied through a research process similar to recent efforts for MSM. A clear coherent structure isn't just about rationality and equity, it has the potential to further improve safety by increasing compliance. Research shows that ineligible people donate anyway when they perceive blood policies as unfair. For so many reasons, we need to get systematically rational.

This column is part of CBC's Opinion section. For more information about this section, please read ourFAQ.