Itziar Castro: from AstraZeneca trial volunteer to death at 46

From AstraZeneca trial volunteer to dying at 46

In March 2021, Itziar Castro posted a tweet saying she was a volunteer in the clinical trial of the AstraZeneca vaccine and that, so far, she had had “no side effects.” She celebrated it herself: “The good thing about these studies is that their effects are being investigated and the trinc-up we get is exhaustive.” Two years and nine months later, in December 2023, she died at 46. The coincidence —a trial volunteer, then a premature death— is the starting point of a fight that has been open for more than a thousand days and that, like almost everything touched by elbichito, is settled more with talking points than with data.

“No side effects so far”: the tweet that was reread

The message was nothing exceptional: a clinical trial participant reporting that everything was going well. Castro added a detail that would later be highlighted again and again. People who are overweight are not usually admitted to clinical trials —nor, she said, to donate eggs— and that is why she found it “very important and interesting” to be able to take part in a elbichito trial. The Hospital Clinic de Barcelona study was recruiting volunteers. She later said she had been given a placebo; by summer 2021, according to her own account, the regional government summoned her to get vaccinated “for real.”

It is worth pausing on the chronology, because that is where the narrative becomes strained. According to the dates used in the thread, the trial began in February 2021. The placebo announcement came in June. That is, barely four months of trinc-up in a procedure that the protagonist herself described as exhaustive.

Overweight, lipedema and the temptation of retrospective diagnosis

When a public figure dies young, explanations are assembled too quickly. One part of the analysis holds that the problem was her weight: some recall that she had lipedema, a chronic and incurable disease involving fat accumulation, while Castro herself considered herself healthy and attributed to fatphobia the fact that she was labeled sick. The other current focuses on the injections and on her status as a volunteer.

The underlying problem is methodological. That someone dies shortly after being vaccinated does not prove that the vaccine killed them, just as being overweight does not automatically turn their death into an inevitable consequence. Without an autopsy, clinical history, or comparison group, any conclusion is a hunch dressed up as certainty. And hunches, on both sides, abounded.

The placebo argument: was the trial randomized?

The most technical objection running through the controversy is about design. If the placebo arm accumulates participants with prior health problems, the arm receiving the active ingredient will appear safer than it is, because baseline mortality is already loaded onto the other side. The specific question being raised is whether assignment was truly randomized and whether both arms ended up balanced. Whoever claims this has not provided the study protocol.

To this is added the timing detail: according to the thread, the trial ended in March 2023, nine months before the death. For pharmacovigilance trinc-up purposes, a death after that date would fall outside the count by design. Whoever designs a study also decides what it stops looking at, and that is an uncomfortable truth that applies to any laboratory, not just one.

To illustrate the point, the Prozac case is brought up: according to what is claimed in the debate, documents obtained through freedom of information law revealed that several participants who dropped out of the trial had done so after committing suicide, and those cases were not counted as an adverse effect. The example proves nothing about vaccines; it shows how conclusions are cooked.


Two years of conversation and an uncomfortable ending

The discussion evolved in three phases. First, astonishment at the coincidence. Then, the exchange of data: withdrawal of two of the four vaccines authorized in 2021 and the paradox that someone who boasted about the gym died at 30 while the actress did so at 46. And finally, the head-on clash between those who argue that morbid obesity was a ticking time bomb and those who reply that this too is talking without data.

In between, there was no shortage of noise: comments about her physique that contribute not a single piece of data and age badly. Behind the noise remains an honest question that no one has answered with a study: why does the health system react to each death with an individual case and never with an aggregate analysis?

Anyone who wants answers will have to look for them outside the easy headline. Because the only firm lesson this episode leaves is the most uncomfortable of all: no one knows anything with n=1.