You may have seen headlines such as “Health Care Worker Had Serious Allergic Reaction After Pfizer’s Covid Vaccine.” It does makes sense to report on such reactions since the Pfizer/BioNTech and Moderna Covid-19 vaccines are still quite new. They’ve received Emergency Use Authorizations (EUAs) rather than full market approval. Just because a vaccine has gotten through the U.S. Food and Drug Administration (FDA) EUA process doesn’t mean that you shouldn’t follow those who are subsequently vaccinated, just in case any new issues emerge.
At the same time, put such case reports in the proper context. A case report is a case report. It’s just one case. For example, just because a 25-year-old man had seizures when solving sudoku puzzles doesn’t mean that you should hide your eyes whenever you see an empty 9 x 9 grid. And just because a man fell butt-first on to an air hose and then got inflated like a Macy’s Thanksgiving Day parade balloon doesn’t mean that you should stay far away from all air hoses or keep your butt cheeks constantly clenched. Whenever you hear of an adverse reaction to vaccine or medication, the big question is how common is it?
Well, according to a recently released report from the Centers for Disease Control and Prevention (CDC), there were 21 cases of anaphylaxis out of 1,893,360 people who had received first doses of the Pfizer-BioNTech Covid-19 vaccine. Anaphylaxis is severe, life-threatening allergic reaction. Typical symptoms consist of a skin rash, nausea, vomiting, difficulty breathing, and shock. Anaphylaxis is a medical emergency. You don’t tell the other person during a date, “oh I am having some anaphylaxis right now, but it happens here and there. Are you eating those last few French fries?” Instead, you should treat anaphylaxis immediately with something like epinephrine to counteract the reaction. Otherwise, you may fall unconscious or die, which would prevent you from getting the last set of French fries anyway.
Clearly, anaphylaxis is not a good thing to have. If someone were to ask you, would you rather deal with anaphylaxis or Anna Kendrick, chose Anna Kendrick. Kendrick may do something strange with your drinking cup while singing “You’re gonna miss me when I’m gone,” but this probably won’t land you in the hospital. But again how common is anaphylaxis after getting the Pfizer-BioNTech Covid-19 mRNA vaccine? Well running the numbers from the CDC study, which pulled data from the Vaccine Adverse Event Reporting System (VAERS) yielded the following number: 11.1 cases of anaphylaxis per million doses of vaccine administered.
If you were told that you had a 11 out of a million chance of getting something, what would your reaction be? Well, when the Lauren Holly character told the Jim Carrey character in the movie Dumb and Dumber that he had a one out of million chance of ending up with her, he did respond, “So you’re telling me there’s a chance. Yeah!” But for most, such chances wouldn’t seem that high at all.
“Any medication or healthcare products can cause allergic reactions,” explained Kimberly G Blumenthal MD MSc, Quality and Safety Officer for Allergy at Massachusetts General Hospital. “So far, we do not see a large risk of severe allergic reactions. It is about 1-2 in 100,000 injections. There is a similar risk of severe reactions to contrast agent that we use every day for CT scans and cardiac catheterizations and other procedures.”
Blumenthal tweeted the following graphic to show the relative risks:
Plus, it’s not as if these severe allergic reactions have gone untreated. Health care personnel probably haven’t said, “oh, that person over there? Yeah, he’s having anaphylaxis. Kind of stinks.” No, they should be trained to handle such reactions. And since 71% of severe allergic reactions have occurred within 15 minutes of vaccination, waiting around the vaccination location for that length of time after getting the jab can help such reactions be caught and treated properly.
The CDC report also mentioned 83 cases of non-anaphylaxis allergic reaction after Pfizer-BioNTech Covid-19 vaccination during the same time period with 87% of them being classified as non-serious. This included itchiness, rashes, scratchy sensations in the throat, and mild respiratory symptoms. These reactions tended to occur fairly soon after vaccination, a median of 12 minutes following the jab. The vast majority 85% emerged within half an hour after vaccination.
A history of allergies or allergic reactions may make you more likely to have an allergic reaction to the Covid-19 vaccine. In the CDC report, at least 67% of those who suffered an allergic reaction after vaccination reported a past history of allergies or allergic reactions. This doesn’t mean that you should forego the vaccine just because you have an allergy to nuts or something else like the television show Keeping Up with the Kardashians. Your decision should depend on what exactly prompts your allergic reactions. The CDC on its website does indicate that you should not get the mRNA Covid-19 vaccine if you’ve already had a severe allergic reaction to any ingredient in the vaccine. So, for example, having a severe allergic reaction after the first dose of the vaccine may mean that you shouldn’t get the second dose. Similarly, a previous allergic reaction to polyethylene glycol (PEG), which is used to encapsulate the mRNA in the currently available Covid-19 mRNA vaccines, may present a problem. This applies to polysorbate may as well which is not in the mRNA Covid-19 vaccines but is closely related to PEG.
“For patients who have severe allergic reactions in the past to a vaccine, or polyethylene glycol or polysorbates, then a pre vaccine visit with an allergist is recommended,” said Paige G. Wickner MD MPH, Medical Director of the Department of Quality and Safety at Brigham and Women’s Hospital. “It is also important that patients who have a possible allergic reaction after dose 1 see an allergist before dose 2.”
Notify a qualified health professional if you have any type of immediate (within four hours of vaccination) allergic reaction The CDC does recommend talking to your doctor when you suffer any type of immediate reaction, regardless of whether it’s severe, to determine what to do about subsequent vaccinations. Having an allergic reaction to the first dose of a vaccine doesn’t necessarily preclude getting a second dose.
Allergic reactions can evolve later as Blumenthal showed in the following tweets:
As Blumenthal indicated, such late reactions don’t necessarily mean that you shouldn’t get vaccinated again either. But it’s a good idea to talk to your doctor about what to do.
When it comes to other allergies, the CDC does recommend “that people with a history of severe allergic reactions not related to vaccines or injectable medications—such as food, pet, venom, environmental, or latex allergies—get vaccinated. People with a history of allergies to oral medications or a family history of severe allergic reactions may also get vaccinated.”
“We understand that there may be confusion and mixed messages for allergic patients across the US,” Blumenthal added. “At many hospitals across the US, allergists have devised protocols to quickly evaluate patients with severe allergy histories prior to their vaccination.” Confusion and mixed messages during the Covid-19 coronavirus pandemic? Imagine that.
Ultimately, the safety of the Covid-19 vaccines is about numbers. Everything in life has its risk, with the possible exception of avocado toast. A pillow could be a deadly weapon. Posting a picture of you eating a hot dog on Instagram could lead to harm if someone else has very strong feelings about hot dogs. This doesn’t mean that avoid all pillows and hot dogs. So far, the risk of severe allergic reactions doesn’t seem to be very high. That doesn’t mean that such reactions shouldn’t be followed and reported. Nevertheless, as the Jim Carrey character in the movie Dumb and Dumber may not have realized, just because there is a chance of something happening, doesn’t meant that it is likely to happen.