Assess the Safety of Administering a Second Dose of a COVID-19 mRNA Vaccine in Individuals Who Experienced a Systemic Allergic Reaction to an Initial Dose

Randomized, placebo-controlled, crossover study to assess risk of recurrence of allergic reactions in individuals who had an immediate systemic allergic reaction after 1st dose of an mRNA COVID-19 vaccine and aiming to explore the underlying mechanism(s) of these reactions.

What Does the Study Involve?

Study consists of 5 visits including initial inpatient visit, 2 telephonic visits and 2 outpatient visits, over the course of 5 months.

During initial visit, eligible participants will be admitted to the NIH Clinical Center in the ICU for 4 days where they will receive the 2nd dose of a COVID-19 mRNA vaccine. They will be closely monitored and treated by trained medical staff in case of reaction. Participants will be closely observed until deemed safe for discharge. Several blood and urine samples will be obtained.

They will then be followed up outpatient at approximately 1 week (telephone), 1 month (in-person), and 5 months (in-person), where they will undergo skin testing and other blood and urine studies. Participants who tolerate 2nd dose of the vaccine without developing a severe allergic reaction will be eligible to receive a booster dose at 5-month visit. 

Who Can Participate?

Participants who suffered from a systemic allergic reaction to the 1st dose of the Moderna or Pfizer-BioNTech mRNA COVID-19 vaccine, and are:

  • 16-69 years old
  • Not pregnant

Where Is It Taking Place?

Clinical Center, National Institute of Health

Is There a Cost?

No cost to the participants. No health insurance required to participate.

Is Compensation Provided?

Yes, patients will receive compensation as well as travel reimbursement.

Number of Visits Required

4 to 5

Steps To Participate

Interested participants can contact our team at: or (301) 761-7565.

Visit for details.

Contact Information

Office: (301) 761-7565
Phone: (800) 411-1222 
TTY: 8664111010 
Hours: 8am – 5 pm

Participating in Research

Watch a series of short informational videos about participating in clinical trials. These videos are intended to help potential participants understand how research works, what questions they should consider asking, and things to think about when deciding whether or not to participate in a study.

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