Moderna’s COVID-19 vaccine rarely causes severe allergic reactions, according to new data released by the Centers for Disease Control & Prevention (CDC).
Between December 21 and January 10, more than 4.04 million people received the COVID-19 vaccine from Moderna, but only ten developed a serious, potentially life-threatening allergic reaction, called anaphylaxis. According to the CDCs, approximately 2.5 cases of anaphylaxis per 1 million people are vaccinated Weekly report on diseases and deaths.
It is not yet clear what causes the severe allergies, but nine out of ten of these cases occurred among patients with previously known allergies (five had previously had anaphylaxis). Most have
allergies to various medicines such as penicillin, but one had environmental and food allergies, and another had no known allergies, according to the report.
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Nine out of ten of the patients developed symptoms – such as vomiting, nausea, wheezing, swelling of the tongue and rash – within 13 minutes of receiving the vaccination, and one developed symptoms within 45 minutes.
All ten patients were treated with epinephrine – a hormone also known as adrenaline, which is the main ingredient in EpiPens and similar motor injectors; four were treated in an emergency department and six were admitted to the hospital, four of which required intubation. However, according to the report, all ten patients have recovered.
“Based on this early monitoring, anaphylaxis after receiving the Moderna COVID-19 vaccine appears to be a rare occurrence,” the authors wrote in the report. But because there is not yet widespread data on COVID-19 vaccines, it is difficult to compare the risk of anaphylaxis with non-COVID-19 vaccines, they write. In a previous Weekly report on diseases and deaths, published on January 15, researchers estimated that the Pfizer-BioNTech vaccine causes anaphylaxis in approximately 11.1 cases per million doses (0.001% chance); the estimate was based on early data.
Yet the anaphylaxis associated with the COVID-19 vaccines from Pfizer and Moderna appears to be above the average number of anaphylactic cases found in previous vaccinations. In 2015, researchers calculated that the chance of developing a severe allergic reaction to a vaccine is about 1.31 per 1 million, according to a 2015 study conducted in the Journal of Allergy Clinical Immunology. “True allergic reactions to vaccines are very rare,” said Dr. Purvi Parikh, allergist and immunologist at NYU Langone Health, previously told Live Science. “Statistically, you are more likely to be struck by lightning than to have a true anaphylactic reaction to a vaccine.” Although the cases are extremely rare – and people should not refrain from getting the vaccine – experts are determining what can cause the allergies.
People who have had an allergic reaction to the first dose of the vaccine should not receive the second dose, the authors write. Vaccination centers must have all the necessary supplies and trained staff to treat anaphylaxis, they write. The CDC also recommends that people receiving COVID-19 vaccines should also be monitored for approximately 15 minutes or 30 minutes if they have a history of allergies or anaphylaxis.
Originally published on Live Science.