According to Stanford University School of Medicine research, allergic reactions to new COVID-19 vaccines based on mRNA are uncommon, usually mild, and should not be a reason to avoid getting vaccinated.
The results will be published online September 17th in JAMA Network Open.
Kari Nadeau MD, PhD, Naddisy Foundation Professor of Pediatric Food Allergy and Immunology and Asthma, said, "We wanted to understand how allergies to the new vaccines were spread and what was causing them."
The study examined 22 possible allergic reactions to 39,000 doses Pfizer and Moderna COVID-19 vaccines that were administered to Stanford health care professionals soon after they received an emergency authorization from the Food and Drug Administration.
The majority of the people who had allergic reactions to COVID-19 vaccine ingredients developed them. They did not have allergies to vaccine components that confer immunity to the SARS virus-CoV-2 virus. These allergic reactions were also caused indirectly by activation of allergic pathways. This makes them more manageable than other allergic reactions.
"It's nice that these reactions can be managed," Nadeau, who directs Stanford's Sean N. Parker Center for Allergy and Asthma Research said. "Having an allergic reaction is rare, but if it does occur, there are ways to manage it."
Christopher Warren, PhD, a former postdoctoral scholar and now assistant professor at Northwestern University Feinberg school of medicine, is the study's main author.
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Nadeau stated that the research suggests ways vaccine manufacturers could reformulate vaccines to reduce allergic reactions.
Instructions for protein-making
COVID-19 vaccines based on mRNA provide immunity through small amounts of messengerRNA, which encode molecular instructions to make proteins. The vaccines contain mRNA, which is fragile. To ensure stability, the vaccines are encapsulated in bubbles of cholesterol and lipids. The mRNA from the vaccine can be injected into the arm of a person. It then enters nearby muscles and immune cells. These cells produce non-infectious proteins that resemble those found on the surface SARS-CoV-2 virus. The proteins activate an immune response, which allows the body to recognize the virus and protect itself against it.
According to the federal Vaccine Adverse Event Reporting System, the rates of severe anaphylaxis (allergic reactions that are serious enough to warrant hospitalization) for vaccines administered by Pfizer and Moderna are 4.7 and 2.5 per million doses respectively. The federal system does not capture all allergic reactions to vaccines and tends to overlook milder or moderate ones.
The Stanford Medicine researchers examined medical records of 38,895 patients who received mRNA-based COVID-19 vaccines between Dec. 18, 2020 and Jan. 26, 2021 to better understand allergic reactions. The vaccines consisted of 31,635 doses Pfizer vaccine, and 7,260 doses Moderna vaccine.
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Researchers searched the medical records of vaccine recipients for any treatment for allergic reactions. They then identified those reactions. 22 recipients, 20 of which were women, experienced possible allergic reactions. This means that they had specific symptoms that began within three hours after receiving their shots. Researchers looked at the medical records of recipients for signs such as hives, swelling of the lips, mouth, tongue, or throat, shortness of breath and wheezing. They also examined the blood pressure and loss of consciousness. Only 17 of 22 recipients experienced an allergic reaction. Three recipients were given epinephrine to treat their severe allergic reactions. All 22 recipients were fully recovered.
One-half of the 22 recipients had documented medical histories of previous allergic reactions. These included 10 to antibiotics and nine to food. Eight to non-antibiotic medications. Some recipients were allergic to more than one type.
Researchers performed laboratory testing on 11 people to determine the type of allergic reaction and what caused it.
Participants underwent skin-prick testing in which a clinician inject small amounts of allergens into their skin. This included lipids, sugars (polyethylenegl or polysorbates), or an entire vaccine. The skin-prick test detects allergic reactions caused by immunoglobin E (or IgE); these reactions are usually associated with severe allergies.
On skin-prick testing, none of the recipients showed any reaction to the vaccine ingredients. Only one recipient had a reaction to the entire COVID-19 vaccine. The IgE antibodies to the vaccine ingredients were not detected in the blood samples of the recipients.
The skin tests failed to explain recipients' allergic reactions so investigators used another diagnostic test. Basophils are a test that looks at allergic activation of immune cell. Ten of the 11 participants had blood samples that showed a reaction against the inert ingredient polyethylenegl (PEG), which is found in the Moderna and Pfizer vaccines. All 11 recipients experienced basophil activation when the whole mRNA vaccine was mixed with their basophils.
The IgG antibodies to PEG were high in all 11 subjects. These antibodies activate basophils under certain conditions. This finding suggests that the subjects were probably sensitive to PEG prior to receiving their vaccines.
Nadeau stated, "What we didn't find is just as important as what we did." "It doesn't seem like the mRNA causes allergic reactions."
She also said that the data suggests that COVID-19 vaccine reactions were not the most severe. This is good news for vaccine safety. All allergic reactions caused by IgG or basophils can easily be treated with antihistamines and fluids. This means that most people who have experienced a reaction to their first dose of vaccine can receive a second dose safely under medical supervision.
PEG is used in many household products as a stabilizer, including cosmetics and medication. Women are more likely to be exposed than men to large amounts of the substance. This could explain why there have been more cases of vaccine allergies among women. Recurrent exposure to a substance can cause allergies and sensitization. Nadeau stated that most allergic reactions were due to PEG and not the vaccine's active ingredients. Therefore, vaccine manufacturers may be able to reformulate vaccines with stabilizers that are less likely cause allergy.
The other Stanford authors of the study are: Alexandra Lee, Mihir Shah and Eric Smith; Iris Chang, medical student; Sharon Chinthrajah; Ruth O'Hara; PhD, dean for research; Brooke Betts; Brooke Betts; Grace Lee; Sharon Chinthrajah; Joseph Gonzalez; Sharon Chinthrajah; Sharon Chinthrajah; Sharon Chinthrajah; Ruth O'Hara; Ruth O'Hara; Ruth O'Hara; Deepak Sisc; Deepak Sindher; Mindytsaiyaiyaiyaiy and of pathology; Mindy Tsaiy, DMSc; and senior research in pathology; Stephen Galli; and of microbiology; and immunology; and, and of pathology; Mindy, DMSc; and of pathology; and of microbiology; and, and of pathology; and of pathology; and of pathology; and of microbiology; and of saiy, DMSc, DMSc, sai, DMSc; and, sai; and of pathology and, sai; and of pathology, and of s.
Nadeau is an associate of the Stanford Institute for Immunology, Transplantation and infection, a senior fellow at the Stanford Woods Institute for the Environment, a fellow at the Stanford Center for Innovation and Global Health, and a member the Bill Lane Center for the American West. Stanford Bio-X is a member of Nadeau, Galli and O'Hara. O'Hara, Galli and Nadeau are all members of Stanford Cardiovascular Institute. O'Hara and Nadeau are both members of Stanford's Wu Tsai Neurosciences Institute. O'Hara and Nadeau are all members of Stanford Maternal and Child Health Research Institute. Sindher, Chinthrajah and Grace Lee are also members. Galli is a member the Stanford Cancer Institute.
This research was also conducted by researchers from the Swiss Institute of Allergy and Asthma Research, University of Zurich, the Department of National Heart and Lung Institute, Imperial College London, and the Centre in Allergic Mechanisms of Asthma.
Research was supported by the Asthma and Allergic Diseases Cooperative Research Centers, the National Institutes of Health, R01AI140134, the National Institute of Allergy and Infectious Diseases SARS Vaccine Study (grant UM1AI10956508) and the Parker Foundation.
