Contribute Try STAT+ Today

The Moderna Covid-19 vaccine, like the one made by Pfizer and BioNTech, appears to induce rare anaphylactic reactions in a small number of people who receive the vaccine, new data from the Centers for Disease Control and Prevention suggest.

As of Jan. 19, there have been 15 confirmed cases of anaphylaxis after receipt of Moderna’s vaccine and 45 confirmed cases of anaphylaxis after receipt of the Pfizer vaccine, the CDC said in a statement to STAT. That works out to a rate of 2.1 cases per million doses of the Moderna vaccine and 6.2 cases per million doses of the Pfizer, according to the agency.

Anaphylaxis is a severe allergic reaction that can be life-threatening if not treated quickly.


“Early monitoring of both the Moderna and the Pfizer-BioNTech Covid-19 vaccines indicate that anaphylaxis following vaccination is a rare event, and although anaphylaxis is serious, it occurs shortly after vaccination (usually within minutes), is readily diagnosed, and effective treatments are available,” the agency said via email.

It noted that the rates at which anaphylaxis is reported following vaccination is likely to change as more vaccine doses are given. In fact, they already have. The first report on U.S. cases of anaphylaxis following administration of the Pfizer vaccine suggested it occurred at a rate of 11.1 cases per million doses given.


In a report published Friday on anaphylaxis cases among people who received the Moderna vaccine between Dec. 21 and Jan. 10, the CDC detailed 10 cases, all of which occurred in women. During the period of study, more than 4 million doses of the Moderna vaccine were administered.

In Friday’s report, six of the 10 people who developed anaphylaxis were hospitalized and four of them needed to be intubated to assist their breathing. None of the people died, the CDC reported. To date there have been no reports of fatal cases of anaphylaxis associated with Covid vaccines in the United States.

All 10 of the people who developed anaphylaxis were given epinephrine, the drug in EpiPens that is used to combat severe allergic reactions. The CDC has said that those administering Covid vaccines need to be equipped to treat anaphylaxis, including having epinephrine injections on hand.

Anaphylaxis occurred quickly in the people affected, with the median time to the start of symptoms being 7.5 minutes. People who receive Covid-19 vaccines are supposed to be monitored for 15 minutes after the injection, with that period extended to 30 minutes for people with a history of severe allergies or anaphylaxis.

Nine of the 10 people had a history of allergies and five of them had previously experienced an anaphylactic reaction.

This story has been updated with additional data and comment from the CDC. 

  • I received my first dose of Moderna 1/8/21. No symptoms after injection. About 1.5 weeks later, I developed what I thought was a bug bite just under where the injection was given. It started to spread and is warm, hard and itchy. It’s been over a week and it hasn’t gone away. I’ve tried hydrocortisone cream. It helps but doesn’t make it go away completely.

    • It sounds like you may have an infection and maybe developing an abscess. It can happen anytime the skin is broken or not properly cleaned before the shot. I personally had the Moderna vaccine also. I have never had my arm that sore after a vaccine and 2 days later still sore like the worst flu shot I have gotten.

  • Received first dose of Moderna on Jan. 16, 2021. Arm was sore for 2 days and developed a bump. 7 days later I developed a large, hot rash. Sorry to hear of others experiencing discomfort. At least I don’t feel alone, majority of articles online say there haven’t been many reactions. I thought my delayed reaction was rarer than it appears.

  • I received moderna vaccine 01/14/2021 the evening of the 21st. I had a small pimple like bump. The next day it started to itch, hot to touch, and a bit swollen. What’s bothersome is the itching. Otherwise, I feel fine. I thought maybe by coincidence it was a spider bite. I’m glad I googled and found this site. I’m not the only one this is happening to.

  • My husband & I both noticed delayed reaction to 1st dose of Moderna (itchy & red bump) like it was swollen again but ~12 days later! We were very surprised, been a few days now and it’s gotten less red but husband still can feel the itch sensation.

  • It’s been 9 days after the first shot. It’s red and itches near the shot area. Not painful. I also took the shot 1-15-2021

  • It’s been 9 days after the first shot. It’s red and itches near the shot area. Not painful.

  • I received the Moderna Vaccine on 1/15/21. I had pain/redness/tenderness at injection site up until 2 days after. My arm was fine after that.
    Now all of the sudden, on day 8 after receiving the vaccine the injection site is very red and spread out on my arm
    ( almost the size of my whole hand.) The area on my arm is hot to the touch, very itchy, hard, and swollen. I am not experiencing any pain or tenderness to the area which is good. I am concerned and wonder if I should seek medical advice. I have now been experiencing these symptoms for 2 full days. I will take the advice of others using ibuprofen and cold compress. Hoping it helps!

  • I am having a similar reaction – hives on my arms, neck and face, 11 days after the vaccine. On about day 9 I developed itching and redness at the injection site. I hadn’t heard about any response like this until coming to this site. Thank you and hope everyone recovers quickly.

    • I had itching at the injection site, for a couple of days. Now, at 7 days out from the shot, the injection site is, once again, itching a great deal. Have you found any information about this delayed itching, since you posted on this site. Thank you.

  • I had my covid vaccine on jan 13th 2021. I didn’t have any side effects but after a week, my arm started to itch where I had vaccine. It that a side effect? Does it i need to consult?

  • I too am having a delayed reaction. Sounds similar, started 8 days after my injection was given. Small bump, then got itchy, red, and hot. I’m taking benadryl and applied lavender and peppermint which seemed to reduce the bump and the irritation.

Comments are closed.