Scientifically accurate and context-sensitive communication of recommendations and public health policy during a pandemic is critical. The recently updated recommendations for COVID-19 vaccines by the National Advisory Committee on Immunization (NACI) is a prime example of how nuances get lost in the game of telephone between official reports and headlines.

The NACI recently updated their recommendations for the use of COVID-19 vaccines, with the primary message that mRNA vaccines are “preferred,” and that people should only take viral vector-based vaccines, such as the AstraZeneca vaccine, if they do not want to wait for an mRNA vaccine — currently the Pfizer-BioNTech and Moderna vaccines. They cited a “safety signal” for the viral vector-based vaccines carrying a rare but serious risk of vaccine-induced immune thrombotic thrombocytopenia (VITT), which is an aggressive type of blood clotting that can lead to serious complications or even death. In Canada, VITT is estimated to occur at a rate of about one case per 100,000 administered doses of the AstraZeneca vaccine.

It is important to note that neither the mRNA nor the viral vector-based vaccines introduce SARS-CoV-2 — the virus that causes COVID-19 — or a modified version of it into the body. They use different methods — RNA-based instructions and a harmless, instruction-carrying virus, respectively — to make the cells in the body produce an innocuous piece of what is called a spike protein, which is found on the surface of SARS-CoV-2. Then, the immune system recognizes the protein parts as foreign bodies and produces antibodies that act as protection when the spike proteins are reintroduced to the body as part of the actual SARS-CoV-2 virus.

The NACI statement contradicts previous public health messaging that the best vaccine is the first one offered to you. It prompted accusations of promoting vaccine shopping, fueling vaccine hesitancy, and deepening healthcare inequities. Many of those who have had their first dose of the AstraZeneca vaccine expressed feelings of betrayal.

How miscommunication leads to bad public health outcomes

NACI is an independent body composed of medical professionals that makes recommendations on the use of newly approved vaccines to the Public Health Agency of Canada and the Canadian government. NACI has an obligation to provide recommendations that reflect the evolving knowledge about COVID-19 vaccines transparently and honestly. Its full set of recommendations was scientifically sound and acknowledged potential social repercussions if proper distribution considerations are not taken. 

However, what reached the general public was a message that assigned preferences to certain vaccines over others — vaccines that have been rolled out and promoted as equal. The recommendation seems to apply to people who have the privilege of waiting for a specific vaccine. Those who can’t wait — essential workers consisting largely of marginalized populations who have already experienced mounting inequities during the pandemic — seem to be stuck with a ‘riskier’ vaccine.

Misleading tweets fuel public distrust in government health agencies. Naheed Dosani, a prominent U of T physician, described taking the AstraZeneca vaccine as “[settling] for a vaccine that has a higher risk of blood clots.” It is due to such statements that people have expressed their frustration and even regret over taking the AstraZeneca dose instead of waiting for a perceived better vaccine.

Aside from the recommendation, NACI also asks the public to do their own risk-benefit analysis. This is not uncommon in healthcare — we do it every time we take an over-the-counter medication. However, when distrust of governmental bodies and misinformation are rampant, this is a complex demand since it requires clear communication of benefits and risks.

A thought experiment in risk-benefit analysis

To do our own risk-benefit analysis of taking a viral vector-based vaccine versus waiting for an mRNA vaccine, firstly we need to weigh our risk of developing VITT against the risks that stem from not taking the AstraZeneca vaccine. The risks include contracting COVID-19, which presents a much higher chance of developing blood clots than the AstraZeneca vaccine according to researchers. We also have to consider the risk of transmitting the virus. 

Many of us feel at least some level of control over whether we contract the virus, and herein lies the first psychological problem; we tend to underestimate risk when we feel in control of the outcome.

We also need to consider the benefits of taking the first available vaccine. However, this was mostly left out of the messaging that reached the public. Including a balanced perspective is a key component of effectively communicating about vaccines. Because of this omission, we are now primed to underestimate the benefits of protecting ourselves and others from COVID-19.

Now we need to weigh the risk of developing VITT if we do take a viral vector-based vaccine. In this scenario, we lose any semblance of control over the outcome, which tends to heighten our risk perception. We’re instead stuck in a waiting game for symptoms of VITT to appear post-vaccination. Additionally, we tend to overestimate rare risks — such as the chance of developing VITT — and underestimate common risks — such as the chance of contracting COVID-19. It also matters how we are feeling at the moment. Fear and anxiety increase our risk perception, whereas anger lowers it. When fear is spread through misleading messaging and bad public health discourse, people aren’t able to make informed healthcare decisions.

Effective public health policy depends on clear communication

We are being asked to calculate a complex, elusive number that could significantly impact our well-being. However, our risk assessment critically depends on how the facts are presented. NACI’s vague and seemingly contradictory advice will deeply affect how we assess the risks and benefits of vaccines at a time when getting through this pandemic will critically rely on addressing people’s questions and concerns about vaccines with honesty and compassion.

Policies and recommendations will likely continue to change as we learn more about the long-term effects of the vaccines. All vaccines currently approved in Canada are very effective at preventing hospitalization and death due to COVID-19. This updated recommendation is not a retrospective commentary; it is a proactive decision as new data emerges. Going forward, informed decision-making about vaccines can only be achieved when the communication we receive is not only scientifically accurate, but also compassionate, balanced, and clear.