Table 1. Characteristics of Documented Cases of 17 Systemic Allergic Reactions, 5 Allergic Reactions, and 3 Control Participants to mRNA COVID-19 Vaccines Administered at Stanford Hospital Between December 18, 2020, and January 26, 2021^a.

Age, y	Sex	Race and ethnicity	History of allergies	History of anaphylaxis	Time to onset, min	Signs and symptoms during the initial reaction	Medications received	Code type	Skin test	Brighton level	Tryptase level, ng/mL	BAT	PEG IgE levels, ng/mL	PEG IgG levels, ng/mL	Time from first dose to blood draw, d
Documented cases of systemic allergic reactions and allergic reactions
20-29	F	White, non-Hispanic	No	No	10	Nausea, tongue edema	Acetaminophen, dexamethasone, epinephrine, famotidine, loratadine	Emergency	NA	2	NA	NA	NA	NA	NA
30-39b	F	Other, Hispanicc	Drug, food	Yes	1	Chest pain, fatigue, headache, heart palpitations	Diphenhydramine, epinephrine, fluticasone propionate	Outpatient	Negative to PEG, P80, and vaccine	1	NA	Positive to PEG and vaccine	<Cutoff	679.9	38
50-59	F	Black, non-Hispanic	No	No	5	Abdominal pain, dyspnea, hypotension, localized erythema, lightheadedness, presyncope, throat and chest tightness, tachycardia, airway swelling	Albuterol, diphenhydramine, epinephrine, famotidine, methylprednisolone	Emergency	Negative to PEG, P80, and vaccine	1	Baseline, 6; after reaction, 25	Positive to PEG and vaccine	<Cutoff	<Cutoff	35
40-49	F	Asian, non-Hispanic	Drug, food, latex	Drug, food	10	Cough, cyanosis, generalized pruritus, localized urticaria, tachypnea	Albuterol, dexamethasone, diphenhydramine, epinephrine, famotidine, naloxone, ondansetron, potassium chloride	Emergency	Negative to PEG, P80, and vaccine	2	Baseline, 4; after reaction, 16	Positive to PEG and vaccine	<Cutoff	349.02	76
50-59	F	Other, non-Hispanicc	Drug	Drug	10	Dizziness, shortness of breath, stridor	Dexamethasone, diphenhydramine, famotidine, lidocaine, magnesium sulfate, morphine, ondansetron, PEG, prednisone	Emergency	Negative to PEG, P80, and vaccine	2	Baseline, 3; after reaction, 20	Positive to PEG and vaccine	<Cutoff	805.02	44
20-29b	F	Native Hawaiian or other Pacific Islander, non-Hispanic	Drug, food	No	30	Generalized pruritus	Cetirizine, diphenhydramine	Outpatient	NA	Skin allergy	Baseline, 5; after reaction: 15	NA	NA	NA	NA
30-39	M	Asian, non-Hispanic	No	No	20	Generalized rash, generalized pruritus	Fluocinonide, loratadine triamcinolone acetonide	Outpatient	NA	Skin allergy	NA	NA	NA	NA	NA
30-39b	F	Other, non-Hispanicc	Drug	No	5	Dizziness, nausea, pharyngitis	Diphenhydramine, metoclopramide	Emergency	Negative to PEG, P80, and vaccine	1	NA	Positive to PEG and vaccine	<Cutoff	6903.24	14
30-39	F	White, non-Hispanic	Drug	No	150	Throat swelling, throat itching, localized angioedema; symptoms more intense following second dose; symptoms recurred at skin test	Diphenhydramine	Emergency	Negative to PEG and P80; positive to vaccine	2	Baseline, 6; after reaction, 19	Positive to PEG and vaccine	<Cutoff	1518.63	6
30-39	F	Other, non-Hispanicc	Drug	No	15	Generalized erythema, face edema, ocular pruritus	Acetaminophen, diphenhydramine, epinephrine, famotidine, methylprednisolone	Emergency	NA	3	NA	NA	NA	NA	NA
30-39	F	Other, Hispanicc	No	No	45	Diaphoresis, generalized urticaria, lightheadedness, nausea	Diphenhydramine	Emergency	NA	1	Baseline, 2; after reaction, 16	Positive to PEG and vaccine	<Cutoff	1097.98	32
30-39	F	Asian, non-Hispanic	No	No	120	Generalized erythema, generalized pruritus	Diphenhydramine, famotidine, hydrocortisone	Emergency	NA	Skin allergy	NA	NA	NA	NA	NA
30-39	F	White, non-Hispanic	Drug, food	No	15	Lightheadedness, localized erythema, localized urticaria, chest pain	Diphenhydramine, levothyroxine sodium	Emergency	NA	1	NA	NA	NA	NA	NA
30-39	F	Asian, non-Hispanic	Drug	No	1	Generalized pruritus, cough	None	Outpatient	Negative to PEG, P80, and vaccine	2	Baseline, 5; after reaction, 21	Positive to PEG and vaccine	<Cutoff	667.56	78
40-49	F	White, non-Hispanic	Food	No	15	Shortness of breath, flushed, rash, difficulty breathing	Epinephrine, prednisone	Emergency	NA	1	Baseline, 3; after reaction, 14	NA	NA	NA	NA
40-49	F	Other, non-Hispanicc	Environmental, food	No	120	Headache, localized urticaria, wheezing	Fexofenadine hydrochloride	Outpatient	Negative to PEG, P80, and vaccine	1	NA	Positive to PEG and vaccine	<Cutoff	491.41	0
40-49	M	Other, non-Hispanicc	No	No	20	Generalized erythema, generalized pruritus, generalized urticaria	NA	Emergency	NA	Skin allergy	NA	NA	NA	NA	NA
40-49b	F	Asian, non-Hispanic	Food	No	15	Generalized pruritus, headache, heart palpitations	Diphenhydramine	Emergency	Negative to PEG, P80, and vaccine	1	NA	Positive to PEG and vaccine	<Cutoff	2439.24	17
50-59b	F	White, non-Hispanic	Drug, food	Yes	5	Oral pruritus, localized erythema, throat tightness	Prednisone	Emergency	Negative to PEG, P80, and vaccine	2	NA	Positive to PEG and vaccine	<Cutoff	679.07	57
50-59	F	White, non-Hispanic	Drug	No	2	Dizziness, tachycardia, hypertension, cough	NA	Emergency	Negative to PEG, P80, and vaccine	2	NA	Negative to PEG; positive to vaccine	<Cutoff	1518.63	68
50-59	F	Other, non-Hispanicc	No	No	90	Hypertension, shortness of breath, palpitations	Ondansetron	Emergency	NA	2	NA	NA	NA	NA	NA
50-59	F	White, non-Hispanic	Drug, food	Drug, food	10	Oral pruritus, rash	Diphenhydramine, famotidine, methylprednisolone	Emergency	NA	Skin allergy	NA	NA	NA	NA	NA
Control Participants
50-59	F	White, non-Hispanic	Drug	Drug	None	None	None	NA	Negative to PEG, P80, and vaccine	None	None	Negative to PEG and to vaccine	<Cutoff	<Cutoff	0
50-59	M	Hispanic	None	None	None	None	None	NA	Negative to PEG, P80, and vaccine	None	None	Negative to PEG and vaccine	<Cutoff	<Cutoff	31
20-29b	F	Hispanic	Food	Food	None	None	None	NA	Negative to PEG, P80, and vaccine	None	None	Negative to PEG and vaccine	<Cutoff	<Cutoff	67

Abbreviations: BAT, basophil activation testing; Ig, immunoglobulin; NA, not available; P80, polysorbate 80; PEG, polyethylene glycol.

^aAllergic reactions were defined as those symptoms that started within 3 hours of vaccination and included hives; swelling of mouth, lips, tongue, or throat; shortness of breath, wheezing, or chest tightness; or changes in blood pressure or loss of consciousness. Reactions were graded using Brighton criteria⁵ for those with systemic anaphylaxis. Tryptase was obtained at baseline in some individuals and within 2 hours for postreaction levels. Specific IgE and IgG to PEG were conducted among participants who consented for a blood draw. The blood draw was used for both the BAT and Ig assays from the same visit for the participant.

^bIndividual received mRNA-1273 vaccine.

^cRaces coded as other in the electronic medical record retained this categorization. No listed races or ethnicities were recoded as other for the purpose of this study.