An online influencer thinks that the answer has to do with “poison.”

The article linked to the Tweet explains exactly why you feel sick after the flu and COVID vaccines, and the answer is not poison.

Why do you feel sick after the flu vaccine vaccines? The flu vaccine works because it stimulates your immune system by tricking it into thinking you’ve been exposed to the actual influenza virus. When that happens, your immune system reacts by creating inflammation, which can cause things like headaches, body aches, and fever. Some vaccines, like flu and COVID, are reactogenic and have a higher chance of causing this than others. Really, it’s just your immune system at work.

But what about the poison? The ingredients of the flu vaccines are often misunderstood, but they are not poisoning people. One ingredient that gets a lot of attention is thimerosal, which is still found in some flu vaccines. Often, people hear “mercury” and think of the kind of toxic mercury you are warned about when eating fish, methylmercury, but thimerosal is made from a completely different compound with different properties. This type of mercury is called ethylmercury, which breaks down relatively quickly and is excreted from the body.

A video is recirculating, spreading fear about COVID vaccines based on one adolescent’s medical experiences while participating in the clinical trial program.

Unfortunately, the family has provided very little in terms of evidence about this teenager’s adverse event. The doctors caring for her have pointed to a possible functional neurological disorder, a diagnosis the family rejects.

Functional neurological disorder (formerly called conversion disorder) is a condition where a person experiences physical symptoms like blindness, paralysis, or numbness that doctors can’t explain through medical tests. These symptoms can happen because of inner emotional conflicts. They often start suddenly after a stressful event. People at risk of this disorder might have other medical or mental health issues.

Immunization Stress-Related Responses (known as ISRR) have been noted in various cultures historically, mostly among children and teenagers. These reactions are affected by social elements like the extent to which vaccination programs are covered in the media. And certainly, COVID vaccination and supposed adverse reactions were common during the early days of the vaccination program.

People with this disorder aren’t faking or intentionally hurting themselves. Some doctors mistakenly think it’s not a real problem, but it is real and distressing. The physical symptoms might be a way for the person to cope with their emotional conflicts.

One Twitter gentleman claims that receiving more than one brand of COVID vaccines over time caused an aneurysm in one young adult.

A study published in The New England Journal of Medicine looked at whether giving an additional booster dose of COVID-19 vaccine was safe and effective for adults who had already received a full vaccination series with any of the three COVID-19 vaccines that were granted Emergency Use Authorization (EUA) or approved by the U.S. Food and Drug Administration (FDA). The study found that giving a booster dose of any of these vaccines was safe and triggered an immune response.

The results from this study led to recommendations from the FDA and the Centers for Disease Control and Prevention (CDC) to allow mix-and-match booster vaccinations in the United States. This means that people could get a different booster vaccine than the one they originally received.

There is no evidence that the COVID vaccine causes brain aneurysms, much less enough that it could be deemed common. Each year approximately half a million deaths from brain aneurysms occur worldwide, about half of them in people under 50.