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A graded dosing protocol allowed two patients with hypersensitivity reactions to the first dose of Moderna's COVID-19 vaccine to receive their second doses safely, researchers said.

The patients -- one with an immediate hypersensitivity reaction managed on site and one needing emergency department transport -- got divided second doses, reported S. Shahzad Mustafa, MD, of Rochester Regional Health in Rochester, New York, and colleagues.

Three to four weeks after receiving the second dose, both patients had IgG antibodies against the spike protein of COVID-19, "suggesting vaccination was efficacious despite the graded dosing protocol," they . One had no reaction to the second dose while the other experience some non-serious allergic symptoms.

CDC recommends against COVID-19 vaccination in people who have immediate allergic reactions to a previous dose of or any component of COVID-19 vaccines. They also recommend against a second dose in people with immediate hypersensitivity reactions to the first dose.

Both of the patients described by Mustafa's group worked in healthcare. One, a 64-year-old woman, had generalized pruritus, urticaria, and self-reported tachycardia within 10 minutes of the first dose of Moderna vaccine. After being treated with 50 mg of oral diphenhydramine, her symptoms resolved within 90 minutes.

The second patient was a woman, age 39, with chest and neck urticaria within 15 minutes of her first dose of the Moderna vaccine, who went on to develop mild facial angioedema within 30 minutes, even after being treated with 25 mg of oral diphenhydramine. She was transported to the emergency department and received 20 mg of intravenous famotidine and 125 mg of methylprednisolone. She was discharged home following 2 hours of observation and no further symptoms.

An allergy practice then performed a skin prick and intradermal testing for polyethylene glycol, polysorbate, and the Moderna vaccine. Both patients were positive for the Moderna vaccine, but negative for the other two components.

Both patients agreed to receive the second dose of vaccine through a graded dosing protocol used with other vaccines. Five injections were given at 15-minuted intervals: the first diluted, the remainder at increasing volumes of full-strength vaccine. The first patient had no symptoms during the protocol; the second reported pruritus after doses 2 and 5, which resolved.

The authors stressed that their experience shows that people with an immediate hypersensitivity reaction can receive the second dose of Moderna vaccine through a graded dosing protocol, and that consultation with an allergy and immunology specialist for evaluation and management may be more appropriate than automatically deferring their second dose.

Limitations included that these cases did not include patients experiencing anaphylaxis after the first dose of Moderna vaccine, and further study is needed to determine if one dose is sufficient in these patients.

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