Here's the latest CDC update clinicians should know when it comes to COVID-19 vaccine reactions

COVID-19 vaccine
The Centers for Disease Control and Prevention advises patients talk to their healthcare providers about prior allergies before they get the COVID-19 vaccine. (Getty/Meyer & Meyer)

At least 21 people in the U.S. have had serious allergic reactions to one of the two COVID-19 vaccines available on the market as the first few million doses of vaccine were administered last month, officials from the Centers for Disease Control and Prevention (CDC) said this week.

"I want to reassure you, this is still a rare outcome," Nancy Messonnier, M.D., head of the CDC's National Center for Immunization and Respiratory Diseases, said during a media briefing Wednesday. 

However, the CDC said, individuals who have a reaction after their first dose of the vaccine should not get the second dose, officials said. What else should clinicians know as they field questions from patients about this new vaccine?  

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Here's a look at what CDC officials had to say:

  • On details of the allergic reactions: The average time between getting a vaccine and having a symptom was 13 minutes, officials said. Most patients who had symptoms saw those symptoms within 15 minutes. Of the 21 patients who had allergic reactions, 17 had a documented history of allergic reactions including to drugs, medical products, food and/or insect stings. The COVID-19 vaccine has a rate of anaphylaxis of 11.1 cases per million cases given. In comparison, the rate of anaphylaxis for patients getting the flu shot is 1.3 per million doses. 
  • On whether allergic reactions were seen with the Pfizer vaccine or the Moderna vaccine: Officials are still looking into that. "At this point, we think that it is something seen with both vaccines, and therefore our recommendations apply to both vaccines," Messonnier said. "As you can imagine, there are tremendous efforts underway right now to understand what might be the cause of this severe allergic reaction. We don't have anything definitive to say. There are lots of hypotheses about it, but for right now this applies to both vaccines." 
  • On whether there are certain folks who should avoid the vaccine: Those who get the vaccine must wait at least 15 minutes to make sure they do not have an adverse reaction, said Tom Clark, M.D., the CDC's vaccine evaluation team lead. "People who have a history of anaphylaxis or history of allergic reactions will need to be observed for 30 minutes," Clark said. "There's a very specific contraindication that if you had an immediate reaction to your first dose, don't get a second dose. And if you have a known allergy to compounds in the vaccine or very closely related compounds in the vaccine, we recommend to not get vaccinated at this time." 
  • Considerations for patients with allergies: "A lot of people have some history of allergy to a bee sting or a food," Messonnier said. "The fact that people in this group had anaphylaxis, had those allergic reactions, may not necessarily mean that those allergic reactions put them in higher risk—but it might. That's why generally our recommendation is that people should be consulting with their healthcare provider. There is a big difference from someone who had a mild allergic reaction in their childhood versus someone who had a severe allergic reaction last week. It's going to be important to have a health clinician to help the patient exercise judgment instead of having a completely hard and fast rule."
  • On addressing vaccine hesitancy among some healthcare workers: "I am definitely concerned that healthcare workers are electing to wait to get vaccinated and, to me, it really makes it exceedingly important that we get the correct information to healthcare workers and that we quickly dispense with misinformation," Messonnier said. "One of the realities of this vaccine is we have limited time that the vaccines were authorized by the FDA and recommended by CDC before they actually hit the shelves. Typically, we have a much longer time to make sure healthcare providers are educated so they can educate their patients. I recognize this all happened quickly and over the holidays. We need to make sure healthcare workers have the correct information. These are safe and effective vaccines. We have good data to show that."