Outsourcing
seem reluctant to clarify why a few unlucky people suffer anaphylactic reactions or blood clots after getting jabbed. Understanding the truth, however, is worth the effort – if only because it shows that the threat of Covid-19 is still far worse than any vaccine.
A shot in the dark? It’s tempting for a layperson without knowledge of immunology to imagine that vaccines are simple – that they’re just the unadulterated active ingredient of a drug. In truth, all pharmaceuticals are also laced with excipients. They may not have a direct role in offering protection against illnesses like Covid-19, but as Viktorija Erdeljic Turk explains, excipients are still vital to the general package. “Excipients are basically everything other than the active pharmaceutical ingredient,” says Turk, a consultant clinical pharmacologist and toxicologist at University Hospital Centre Zagreb. In practice, Turk continues, this encompasses everything from chemicals that contribute to a drug’s biopharmaceutical profile to ones that change its appearance.
What about the excipients in Covid-19 vaccines? That depends on the drug. The AstraZeneca jab contains a common excipient known as polysorbate 80, which increases its stability. The Moderna and Pfizer-BioNTech mRNA vaccines, for their part, contain another stabilising excipient called polyethylene glycol. As Lene Heise Garvey explains, that’s important because of how they work. Like viral vector vaccines, they enable cells to make a protein that triggers an immune response specific to, in this case, Covid-19. A vital component necessary for making that happen are fatty molecules called lipid nanoparticles, which mRNA vaccines use in place of modified viral vectors like AstraZeneca’s adenovirus. These LNPs disguise the mRNA so that it isn’t recognised by the body as foreign matter and destroyed.
Polyethylene glycol helps combine the mRNA and the lipid nanoparticles. As Garvey, an associate professor at the University of Copenhagen, puts it: “The lipid nanoparticles have to be intact for this messenger RNA to go into the cells, and the polyethylene glycol holds them together.” All well and good. But that still leaves one question unanswered: what do these different excipients have to do with serious reactions to vaccines? It turns out the answer is potentially quite a lot. Though it’s common across the food and pharmaceutical industries, for instance, polysorbate 80 has occasionally been linked to serious reactions in users, including anaphylaxis. At the same time, polyethylene glycol might come with similar risks. We already know, after all, that penicillin and laxatives can cause anaphylaxis, and that they contain polyethylene glycol.
World Pharmaceutical Frontiers /
www.worldpharmaceuticals.net
By December 2020, no reactions to polyethylene glycol had been reported in vaccines – but then again, the Moderna and Pfizer Covid-19 vaccines are among the first to contain the excipient. One potential risk is that, due to structural similarities, polyethylene glycol and polysorbate 80 can spark cross-reactivity. This, in effect, means that though someone is allergic to polysorbate 80, exposure to polyethylene glycol makes them react in a similar way. What is certain, at any rate, is the danger of allergic reactions like anaphylaxis. At best, it can encourage rashes and wheezing. At worst, it can trigger cardiac arrest and death. And that’s before you consider the blood clots that killed Tanya Smith, which could have been the result of a misguided assault by her own autoimmune system.
People are asked to wait around for 15 minutes after injection in case they show signs of anaphylaxis.
“The lipid nanoparticles have to be intact for this messenger RNA to go into the cells, and the polyethylene glycol holds them together.”
Lene Heise Garvey, University of Copenhagen A right jab
Given these potential dangers, how should a responsible public approach Covid-19 vaccines? Both Turk and Garvey suggest looking at the numbers. A fair point, even if you only consider a single country. In the US, for example, just one of the 18,801 participants in a late-stage trial for the Pfizer vaccine had an anaphylactic reaction. These numbers reflect a broader truth: vaccines can harm you, but only if you’re extremely unlucky. As a 2015 study by the Centers for Disease Control and Prevention (CDC) found, 33 confirmed cases of vaccine-triggered anaphylaxis were found among 25 million doses. That translates to a rate of just 1.3 cases for every million doses. No wonder Turk emphasises that the risk of anaphylaxis is
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