Fact check: What are the known long-term side effects of mRNA vaccines?

1. Summary of the results

The known long-term side effects of mRNA vaccines are not clearly established ^[1]. According to the systematic review, most mRNA COVID-19 vaccine adverse events are mild or moderate and occur shortly after injection, such as injection-site pain, fatigue, headache, myalgia, and fever ^[1]. Rare severe events like myocarditis/pericarditis, Guillain-Barré syndrome, cerebral venous sinus thrombosis, and allergic reactions have been reported, but a direct causal link is not firmly established, and these events are acute ^[1]. Another study, the large multinational GVDN cohort of 99 million vaccinated individuals, found increased observed-vs-expected rates for acute conditions, including myocarditis, pericarditis, Guillain-Barré syndrome, CVST, and ADEM, within 0-42 days post-vaccination ^[2]. However, this study provides no evidence of persistent or long-term sequelae ^[2]. Both analyses suggest that the benefits of vaccination outweigh the rare short-term risks ^[1] and that most safety signals are short-term ^[2].

2. Missing context/alternative viewpoints

Some key points to consider are the timeframe for evaluating long-term side effects, as the GVDN cohort study only evaluated adverse events within 0-42 days post-vaccination ^[2]. Further follow-up is needed to determine any long-term effects ^[2]. Additionally, the systematic review highlights that no clear long-term side effects have been demonstrated ^[1], which may not necessarily mean that there are no long-term side effects, but rather that they have not been identified or studied yet. It is also important to consider the population being studied, as the GVDN cohort includes 99 million vaccinated individuals ^[2], which may not be representative of all populations. Alternative viewpoints may include considering the potential long-term effects of mRNA vaccines on specific subpopulations, such as children, older adults, or individuals with underlying health conditions.

3. Potential misinformation/bias in the original statement

The original statement asks about the known long-term side effects of mRNA vaccines, which may imply that long-term side effects exist. However, according to the analyses, no clear long-term side effects have been demonstrated ^[1], and most safety signals are short-term ^[2]. This framing may benefit vaccine skeptics who may use the lack of information on long-term side effects to argue against vaccination. On the other hand, the emphasis on the benefits of vaccination outweighing the rare short-term risks ^[1] may benefit public health officials and vaccine manufacturers who prioritize vaccination as a crucial tool for preventing COVID-19. A more nuanced understanding of the available data and its limitations is necessary to accurately inform the public about the risks and benefits of mRNA vaccines ^{[1] [2]}.