Clinical Cases in Pharmacology Clinical Cases  ·  Allergy and Immunology Vol. III  ·  Immune Hypersensitivity Disorders  ·  Angioedema After Dose One: Testing First, or Just Splitting the Second Dose
Allergy and Immunology Vol. III, Case AIAutoinflam-0008 — Immune Hypersensitivity Disorders

Angioedema After Dose One: Testing First, or Just Splitting the Second Dose

A positive or negative allergy test would genuinely change how her second dose gets given — the argument is whether she can afford the days it takes to get one.

Abbreviations, terms, and other agents mentioned in this case PEG — polyethylene glycol — an excipient in the lipid nanoparticle formulation of mRNA vaccines  ·  IM — intramuscular  ·  DMARD — disease-modifying antirheumatic drug
Presentation

Grace O., a 52-year-old woman who has managed psoriatic arthritis on adalimumab for four years, developed facial and lip swelling, diffuse urticaria across her trunk and arms, and a sensation of throat tightness roughly twelve minutes after her first dose of the Pfizer-BioNTech mRNA COVID-19 vaccine. She was treated on-site with intramuscular epinephrine, an H1-antihistamine, and several hours of observation, with full resolution of symptoms and no biphasic recurrence — a real and adequately treated reaction, not one she simply rode out on her own. A serum tryptase drawn ninety minutes after symptom onset came back mildly elevated relative to her own previously documented baseline, supporting a genuine mast-cell-mediated event rather than a vasovagal or anxiety-related reaction that happened to coincide with the injection. She has never knowingly taken a polyethylene glycol-containing product before — no history of using PEG-based laxatives, no prior surgery requiring a PEG-containing bowel preparation — which leaves her clinical history genuinely uninformative about whether PEG — the excipient Banerji and colleagues' 2021 mass-vaccination allergy protocol singled out as the most likely culprit in exactly this reaction pattern — is actually her trigger.

Being on adalimumab for four years, with well-controlled joint disease but a documented immunosuppressed state, is precisely what makes completing her vaccination series matter more than it would for someone off biologic therapy — not a modifying detail on the side of the case, but the fact actively raising the stakes of whichever way this decision goes. Community case counts in her area have been rising for three weeks, a real, current exposure risk rather than a background statistic, and her rheumatology team has not identified any reason to interrupt her adalimumab in the meantime. She has also asked, directly and more than once, whether a non-mRNA vaccine platform would sidestep the question entirely — a reasonable option in principle, but one the team notes would still leave the PEG-versus-other-excipient question unanswered for any future mRNA exposure she might need.

PEG/polysorbate skin testing, if arranged, could meaningfully change how her second dose is approached — but whether that test is realistically available before a delay itself becomes the more consequential decision is not yet known to anyone at this visit.

Grace O. · 52 Dose 1 Reaction, Dose 2 Pending
Reaction
Facial/lip angioedema, urticaria, throat tightness ~12 min post-dose 1
Treatment given
IM epinephrine, antihistamine, observed — resolved, no biphasic reaction
PEG exposure history
No known prior exposure to PEG-containing products
Immunosuppression
Adalimumab x4 years for psoriatic arthritis, well-controlled
Community exposure risk
Rising local case counts, past 3 weeks
Skin testing access
Availability and turnaround time not yet confirmed
Rheumatologic status
No indication to interrupt adalimumab currently

What testing would actually change, and how fast it can happen

Allergist Opening

Throat tightness is the detail I don't want to move past quickly. That's a genuinely more serious reaction than urticaria alone, and it's exactly the kind of case where PEG or polysorbate skin testing gives us real, actionable information — a positive result would push us toward avoidance or a much more conservative graded protocol, and a negative result would let us proceed with real, if imperfect, reassurance.

Rheumatologist Response

I agree the reaction was serious enough to take seriously, but I want to name what testing costs her: she's on a biologic, community case counts are rising, and every week she goes without a second dose is a week of real exposure risk in a genuinely immunosuppressed patient. Skin testing also isn't perfectly predictive — a negative result doesn't fully exclude risk on rechallenge.

I'm not arguing against testing in principle. I'm arguing that treating it as a prerequisite, rather than something to pursue in parallel with a graded-dose plan, assumes a delay has no cost — and for her, it clearly does.

Infectious Disease Physician Final

I think the actual disagreement here is really about a fact neither of you has confirmed yet: how quickly testing can happen. If an allergy clinic can see her this week, get the result — it directly changes which graded protocol is safest, and a week's delay against her current exposure risk is a real but bounded cost.

If testing access realistically means several weeks, I'd side with proceeding now on a conservative split-dose protocol under observation, because an open-ended delay is a materially different cost than a short, defined one. I'd find out which situation we're actually in before deciding between you.

Regimen selected
PEG/Polysorbate Skin Testing (Referral Placed)
Diagnostic Allergy Testing · Urgent referral
Placed as an urgent rather than routine referral, directly addressing the Infectious Disease Physician's proposed decision point of realistic turnaround time.
Graded-Dose Vaccination Protocol — Contingent
Split-Dose mRNA Vaccine, Observed · Timing dependent on testing turnaround
Named as the plan if testing cannot be arranged promptly, or as the informed next step if testing returns negative — not offered as an unconditional default in either direction.
Continued Adalimumab
TNF-α Inhibitor · Unchanged
No indication to interrupt her underlying disease treatment while the vaccination decision is being resolved.
Permanent Vaccine Avoidance — Not Adopted
Alternative Considered, Not Selected
Not chosen outright; would only become the leading option if skin testing returns clearly positive, which is not yet known.
Where this was left

An urgent allergy referral was placed the same day, with the team agreeing to proceed on whichever path the testing turnaround time actually supports rather than deciding the dosing question in advance — the Infectious Disease Physician's reframing accepted by both other voices as the right way to resolve, rather than split, their disagreement.

Not yet known at the time this plan was made: the actual test result and its turnaround time, both of which the team explicitly agreed would determine the next step rather than assume in advance. The Allergist and Rheumatologist agreed that whichever timeline turns out to be real, they would revisit the specific graded-dose protocol together once it is, rather than let today's disagreement decide it in the meantime.

Educational content only — a composite teaching case, not a real patient encounter or a substitute for clinical guidance. About These Cases →