Experts have taken to social media to quell misinformation and address common concerns about Pfizer’s messenger RNA (mRNA) COVID-19 vaccine, performing an important public service in support of robust vaccine uptake. However, some scientific information is being oversimplified to the point that it is misleading. The public’s decision to take a vaccine whose long-term risks are unclear should be a well-informed one. Clear communication is crucial to the process of informed consent and for building public trust in the fight against vaccine hesitancy.

Take, for example, a video posted to Twitter by a bioengineer working on COVID vaccines. Presented as “Three facts about the long-term effects of the COVID vaccine,” the researcher makes a case for the long-term safety of RNA COVID-19 vaccines. mRNA carries the instructions for making proteins and is a normal part of protein production in the body. mRNA COVID-19 vaccines deliver synthetic mRNA into the body, which tells cells to make one of the COVID-19 surface proteins – which they do. The immune system then produces an immune response to this protein, preparing the body to fight the actual virus in the future.

Fact No. 3 in the Twitter video suggests that because the RNA drug Onpattro received U.S. Food and Drug Administration (FDA) approval in 2018, has a similar formulation to RNA COVID-19 vaccines and is safe long-term, RNA COVID-19 vaccines are also safe long-term.

Indeed, Onpattro – used to treat a fatal rare neurological disorder by interfering with the RNA instructions for making an abnormal protein – and Pfizer’s vaccine are similar in that they are both “RNA in a lipid nanoparticle” that affect protein production in the body.

However, the safety comparison between Onpattro and mRNA COVID-19 vaccines is oversimplified and misleading. It implies that we can rely on the Onpattro clinical trials for assurance that all “RNA in a lipid nanoparticle” technology is safe. But the long-term safety of one type of RNA technology does not mean that another is equally as safe. If that were the case, RNA vaccines would not require independent testing to the extent that they do.

The conditions of different clinical trials can vary widely, especially when the underlying medical disorder is different. Such variations include study design, criteria for selecting research participants, and outcome measures for safety and efficacy. Here’s one example of how the Onpattro trials differ from Pfizer’s COVID-19 vaccine trials: Participants in Onpattro’s trials were pre-medicated with steroids and antihistamines to minimize infusion-related reactions to treatment. Pfizer’s clinical trial participants were not because suppressing an immune reaction in a vaccine trial goes against the principles of the therapy. In fact, the exclusion criteria for Pfizer’s trial makes anyone taking steroids or other immune suppression therapy ineligible.

This difference alone is enough to question the comparison between Onpattro’s safety and RNA vaccine safety. Pre-medication with steroids and antihistamines before receiving an “RNA in a lipid nanoparticle” therapy may improve the treatment’s safety profile. In this respect, directly comparing the safety profiles of Onpattro and RNA vaccines is unreliable.

While the concept of RNA manipulation for treating or preventing disease is not new, the FDA has never before approved a commercial vaccine made from RNA. Shorter-term safety has been shown for the Pfizer vaccine but we do not yet have information about possible longer-term side effects, because we have not yet reached long-term milestones for safety testing. The estimated completion date for the current Pfizer clinical trial is January 27, 2023. Even so, it does not include specific outcome measures for safety at the 1- or 2-year time points. We cannot know about long-term effects until we reach the long-term in clinical trials designed to gather specific safety data. Inferring long-term safety from Onpattro’s clinical trials is just that – inference, not evidence.

Moreover, there remain many outstanding questions about these vaccines that require further research. For example, Canada’s National Advisory Committee on Immunization outlines a list of research priorities for COVID-19 vaccines, including those related to efficacy, safety and immunogenicity. This is not to say that people should necessarily wait to be vaccinated until long-term safety is known, but rather that scientific information be communicated fully and clearly so that the public has an opportunity to adequately weigh the risks and benefits of their decision.

Fighting misinformation and vaccine hesitancy requires a balanced and unbiased presentation of facts to uphold informed consent principles. In our efforts to present science in an easily understandable way, let’s remain mindful of the pendulum of misinformation and prevent it from swinging too far in the opposite direction.

Iris Kulbatski is a science writer. 

Image credit: Shutterstock.com