Life-threatening allergic reaction to mRNA COVID-19 vaccination is rare, limited study suggests

Not long after the first mRNA-based COVID-19 vaccines were given a nod for emergency use and shot to people outside their clinical trials, many reports pointed to anaphylaxis – a life-threatening system-wide allergic reaction to compound(s) in the vaccine. A new study attempts to address the widespread concerns about anaphylaxis after the mRNA COVID-19 shot. Estimated to occur in 2.5 to 11.1 cases per million doses of mRNA vaccines, anaphylaxis is a reaction mostly limited to people with a history of allergy, according to the study's findings. However, concerns about allergy have contributed to vaccine hesitancy, as per the new research.Over 60,000 mRNA COVID-19 vaccine doses administered to health workers were studied by the researchers, for symptoms of an acute allergic reaction. All the volunteers who experienced anaphylaxis, recovered, as per the study, without going into shock or needing intubation to combat trouble breathing.The vast majority of volunteers (98 percent) did not have any symptoms of an allergic reaction after receiving getting an mRNA COVID-19 vaccine. While the remaining 2 percent reported some allergic symptoms, severe reactions indicating anaphylaxis were reported at the rate of 2.47 per 10,000 vaccinations. This statistic – the rate of anaphylaxis noted in the study – is much higher than earlier reported by the US Centres for Disease Control and Prevention (CDC) from passive reporting methods [between 0.025-0.11 per 10,000 vaccinations].[caption id="attachment_9405621" align="alignnone" width="1280"]

Anaphylaxis is a serious and life-threatening allergic reaction and can occur within minutes after you are exposed to something you are allergic to.. Image Credit: Bernstein Allergy Research[/caption]People who got the mRNA vaccine followed by an anaphylactic episode usually had histories of allergy. Nearly a third of this affected group (31 percent) had a history of anaphylactic attack(s), and an alarming fraction (94 percent) of the affected group were female.The researchers also say in the study that the overall risk of anaphylaxis from an mRNA COVID-19 vaccine dose remains very low – comparable to what is expected in other common "health care exposures". Some of the most frequently-linked allergies that cause anaphylaxis are food, insect stings, medications and latex, according to the American College of Allergy, Asthma & Immunology website.There were many factors limiting the scope of the study. First, the use of self-reported data from participants – a measurement or standard exam would offer a less subjective means of comparison than an interview or questionnaire, like used in the study. This also led to missed cases of potential anaphylaxis, by the study authors' own admission. The volunteers in the study were also a northeastern US cohort, which cannot be generalizable to the general population of the US, let alone the world.