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While criteria for contraindication to COVID-19 mRNA vaccines are narrow, more observation or possibly delayed vaccination may be necessary in those with a history of severe allergic reactions, CDC staff said on a call with clinicians on Friday.

The only individuals who should not receive mRNA COVID-19 vaccines, such as the recently authorized Pfizer/BioNTech vaccine and Moderna's similar product, are those with a history of severe allergic reaction, including anaphylaxis, to components of the vaccine. For example, CDC staff highlighted polyethylene glycol, which is often used in laxatives.

However, those with a history of severe allergic reaction to another vaccine or an injectable therapy may receive the vaccine, but with precautions.

Given recent publicity surrounding anaphylactic reactions to the Pfizer vaccine, CDC staff discussed an algorithm for the triage of individuals presenting for mRNA COVID-19 vaccines.

A risk assessment and potential deferral of vaccination applies only to those with a history of these severe vaccine-related allergies or severe allergies to other injectable therapies. However, the following groups may proceed with vaccination:

• Individuals with a history of food, pet, insect, venom, environmental, latex, or other allergies unrelated to vaccines or injectable therapies
• History of allergy to oral medications
• Non-serious allergy to vaccines or injectables
• Family history of anaphylaxis
• History of anaphylaxis not related to vaccines or injectable therapy

CDC clinical guidance recommends a 30-minute observation period for those with a history of severe allergic reaction, including anaphylaxis, due to any cause, and a 15-minute period for those with an allergic reaction, but not anaphylaxis.

For those with a history of severe allergies to vaccines or injectable therapies, a 30-minute observation period is recommended.

Sarah Mbaeyi, MD, of the CDC, offered advice on how to distinguish what constitutes an allergic reaction severe enough in which vaccination is not recommended.

"Some things like eliciting 'did it require an EpiPen? Did it require hospitalization or a visit to the emergency department?' or trying to elicit symptoms to see how severe the allergic reaction might have been," she said.

Mbaeyi also recommended a discussion to understand what happened and take into account the various factors before determining whether or not they should be vaccinated. She added if an individual experiences anaphylaxis following the first dose, the person should not receive the second dose.

Given highly publicized cases of anaphylaxis, Amanda Cohn, MD, of the CDC, emphasized the importance of having proper medications and supplies at vaccination sites, though at minimum, those administering the vaccine should be able "to recognize anaphylaxis, administer epinephrine appropriately and call emergency services."

Even if anaphylaxis is only suspected, individuals should receive epinephrine, though Mbaeyi noted some older adults with cardiac issues, such as those in long-term care facilities, are more at risk of side effects.

In addition to allergies, those with an immunocompromising condition, and pregnant or lactating women may be vaccinated. Mbaeyi noted there are limited data on the vaccine in immunocompromised individuals and "the vaccine might not work as well." The same is true for those with autoimmune disease or those taking biologics. However, these individuals were eligible to enroll in vaccine clinical trials, and may be vaccinated.

Cohn also discussed delaying vaccination 90 days after treatment among those patients recovering from COVID-19 who were treated with monoclonal antibodies or convalescent plasma, which may help the vaccine avoid interference with immune responses.

Both mRNA vaccines are two-dose regimens, though Pfizer's is administered 21 days apart, and Moderna's 28 days apart. CDC staff said it is not necessary to restart a series, regardless of how much time elapsed after the first dose. However, they do not recommend co-administration of other vaccines, such as the flu vaccine, with mRNA vaccines. They should be given either 14 days before or after the COVID-19 vaccine.

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