Maintaining Safety With SARS-CoV-2 Vaccines
abstract
This abstract is available on the publisher's site.
Access this abstract nowTo date, the development of mRNA vaccines for the prevention of infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a success story, with no serious concerns identified in the ongoing phase 3 clinical trials. Minor local side effects such as pain, redness, and swelling have been observed more frequently with the vaccines than with placebo. Systemic symptoms such as fever, fatigue, headache, and muscle and joint pain have also been somewhat more common with the vaccines than with placebo, and most have occurred during the first 24 to 48 hours after vaccination.1 In the phase 1–3 clinical trials of the Pfizer–BioNTech and Moderna mRNA vaccines, potential participants with a history of an allergic reaction to any component of the vaccine were excluded. The Pfizer–BioNTech studies also excluded participants with a history of severe allergy associated with any vaccine (see the protocols of the two trials, available with the full text of the articles at NEJM.org, for full exclusion criteria). Hypersensitivity adverse events were equally represented in the placebo (normal saline) and vaccine groups in both trials.
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mRNA Vaccine Safety
As we rapidly move from COVID-19 vaccination at large tertiary care health centers to vaccination at clinics, pharmacies, and other ambulatory sites, attention must be given to an emerging challenge. Anaphylaxis has been documented at a rate of about 1 case per 100,000 doses of the Pfizer/BioNTech mRNA COVID-19 vaccine. This is roughly 10-fold higher than the rate with other vaccines.1
Some adverse effects are to be expected: fever, fatigue, headache, muscle aches, and joint pain have been relatively common in the first 1 to 2 days following vaccination. These symptoms are self-limited and often respond to acetaminophen or NSAIDs. The occurrence of flushing, hives, laryngeal edema, wheezing, nausea, vomiting, tachycardia, hypotension, and/or cardiovascular collapse represents a medical emergency for which rapid administration of epinephrine and antihistamine are needed along with other supportive care.2
Understanding the mechanism of mRNA vaccine–related anaphylaxis is beneficial. Castells and Phillips1 provide a succinct overview of proposed pathways leading to anaphylaxis as well as a detailed table describing the vaccines and their chemical components. A purported culprit is underlying allergy to polyethylene glycol. More insight will likely emerge over the coming weeks.
An appreciation of recent cases helps to better anticipate this phenomenon.3 Of 21 cases reported, 90% were in females and the median age was 40 years (range, 27–60). The media time to onset of anaphylaxis was 13 minutes (range, 2–150) with 71% and 86% of cases occurring within 15 and 30 minutes, respectively. Importantly, 81% had documented histories of allergies or allergic reactions.
Being prepared for the rare event is crucial. We rarely see anaphylaxis in primary care. Moreover, we are unlikely to see this following COVID-19 vaccinations. Nevertheless, preparedness is key. A great and brief overview of management is available,2 which includes guidance on emergency equipment that should be immediately available at the venue of vaccination.
Finally, primary care clinicians and their vaccinating colleagues need to become familiar with who can and who should not receive mRNA COVID-19 vaccines, and who may receive the vaccine with added precaution. I direct readers to “Appendix A: Triage of persons presenting for mRNA COVID-19 vaccination” for guidance on underlying conditions and allergy history.4
The time for expansion of vaccination has arrived. We need to be fully prepared.
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