Some Reactions to COVID Vaccines Expected, But No Reason To Avoid Shot

Updated Dec. 20: As COVID-19 vaccines roll out across the U.S., there are likely to be more reports of possible allergic reactions, experts say.

Yet those reports should not deter the vast majority of people – including people with severe food or medication allergies – from getting the vaccine. When deciding to get vaccinated, allergists say it’s important to weigh the risks of a COVID-19 infection with the small risk of reacting to the vaccine. At this time, the risks from the virus far outweigh the risk of a reaction to the vaccine.

“We know COVID-19 is a really severe infection, even young adults can have severe symptoms, can be hospitalized, have an ICU admission, and have died,” says Dr. Rebecca Saff, an allergist at Massachusetts General Hospital in Boston. “So with the risk of having an allergic reaction, you would want to be cautious with monitoring, but the risk from COVID is much greater. We really want people to be vaccinated.”

There have been three reports of likely allergic reactions in the U.S. and Britain, with the mRNA-based Pfizer-BioNTech vaccine for coronavirus. All three – including two in Britain on Dec. 8, and two health-care workers at an Alaskan hospital on Dec. 15 – were treated for anaphylaxis with epinephrine and have recovered. “This should be very reassuring to our patients,” Saff adds.

2nd Vaccine Moves Forward

On Dec. 17, a panel of experts that advises the U.S. Food and Drug Administration voted to recommend an emergency use authorization (EAU) for a second COVID-19 vaccine, made by Moderna. The FDA then gave its authorization to the Moderna vaccine on Friday evening.

The vaccine uses similar mRNA technology to the Pfizer vaccine, and would be given to adults ages 18 and up. Like the Pfizer vaccine, which has been authorized for those ages 16 and older, the Moderna vaccine also requires two doses, several weeks apart.

Amid the excitement that the vaccines herald an eventual end to the pandemic, recent reports of anaphylaxis have stirred up worries about potential vaccine side effects, particularly in the allergy community.

Both British health workers who reacted had a history of serious allergic reactions, one to foods and the other to unspecified medications.

On Dec. 15, a nurse in Alaska experienced symptoms consistent with anaphylaxis – shortness of breath, flushing, and a rash – moments after receiving the shot. The woman, who has no history of allergies, became the first U.S. report of an adverse reaction. The same day, a second health-care worker also experienced eye puffiness, lightheadedness and a scratchy throat. His reaction was not as serious and quickly resolved.

Clinical trials of the Pfizer vaccine involving almost 44,000 people indicated that there were slightly more instances of possible allergic reactions in those who received the vaccines compared to those given the placebo, although the reactions were mild and did not require epinephrine, according to an FDA official.

The FDA warns only two groups not to get the Pfizer vaccine: those with a known history of a severe allergic reaction to a component of it, plus anyone who has a serious reaction to the first dose of the two-dose inoculation. During the advisory panel meeting, FDA officials said there were no plans to add new restrictions.

“While the totality of data at this time continue to support vaccinations under the Pfizer EUA [emergency use authorizations] without new restrictions, these cases underscore the need to remain vigilant during the early phase of the vaccination campaign,” said Dr. Doran Fink, deputy director for clinical review at the FDA.

Saff also recommends that anyone with a history of a severe allergic reaction to a vaccine consult with their allergist prior to getting the shot.

Fact Sheets Revised to Stress Precautions

As with all vaccines, the Centers for Disease Control and Prevention recommends that vaccine sites have epinephrine, a blood pressure cuff, antihistamines and oxygen on hand to treat anaphylaxis. “Just in case a reaction occurs it can be diagnosed quickly and managed appropriately,” said Dr. Jay Butler, the CDC’s deputy director for infectious diseases.

The recommended observation period for anyone receiving the vaccine is 15 minutes. Initially, the CDC only those with a history of severe reactions to any vaccine, needed a 30-minute observation after injection. On Dec. 20, the CDC revised that recommendation to say that anyone with a history of anaphylaxis “due to any cause” should be observed for 30 minutes.

In the case of the Alaska woman, the CDC and FDA are working together to determine the cause of the reaction. During a Dec. 16 briefing, Butler said the agency will continue to monitor COVID-19 vaccine safety, “and will be transparent with the communications.”

The FDA’s Fink said regulators are working with Pfizer to revise fact sheets and prescribing information to emphasize the requirement that facilities administering the vaccine have the ability to immediately treating any severe allergic reaction.

What happened in Alaska?

In the first Alaska case, the woman who reacted first felt flushed about 10 minutes after getting the shot, says Dr. Lindy Jones, the emergency physician at Bartlett Regional Hospital in Juneau who treated her.

She was given epinephrine and transferred to the emergency room, where she experienced shortness of breath but not wheezing and had an elevated heart rate. As well, “she had a red, flushed rash over her face and torso,” Jones says. “I was concerned about an anaphylactic reaction.”

After the epinephrine, her symptoms improved, but then re-emerged about a half hour later. Throughout the reaction, her blood pressure and oxygen saturation levels remained normal, Jones says. She was put on an epinephrine drip and treated with steroids. A day later, the woman was off all medications.

Saff says it was a good sign that the woman’s vital signs were stable during the episode. Her symptoms and rapid improvement after epinephrine strongly suggest the woman had an allergic reaction, but further evaluation is needed to know. One method of confirming it is to measure tryptase levels in the blood. High tryptase levels are an indicator of an IgE-mediated allergic reaction.

Zeroing In on the Cause

With millions of North Americans likely to be vaccinated with the Pfizer vaccine in the coming months – and more reports of reactions expected – it’s important to hone in on what’s causing the reactions, experts say.

As of Dec. 17, more than 1.5 million doses had been distributed nationwide, according to the Department of Health and Human Services.

Studies show that the rate of severe allergic reactions to vaccines is about 1 in 1 million. With the vaccine in its early stages of rollout, it’s too soon to tell if the rate of reactions for the Pfizer vaccine will be similar to vaccines in use for decades, says pediatric allergist and researcher Dr. Brian Vickery.

“The best data [on the Pfizer vaccine] is from the Phase 3 trials,” says Vickery, director of the food allergy center at Children’s Healthcare of Atlanta. “The rate of systemic reaction between the placebo and the treatment group was different by a fraction of 1 percent. That’s very reassuring to me.”

Allergists stress that the underlying cause of the reactions are still being investigated. Neither vaccine uses any food proteins, animal products or preservatives.

Both the Pfizer and Moderna vaccines are made of snippets of genetic code encased in a fatty covering called a lipid. The Pfizer and Moderna vaccines also include polyethylene glycol (PEG), a compound found in many cosmetics and medications. PEG has been implicated in rare cases of severe allergic reactions.

The version of PEG in the Pfizer vaccine has not been used before in a vaccine, Saff notes, adding that Moderna vaccine also includes PEG, but a different version.

Anaphylaxis can occur for reasons other than what is considered an allergic reaction, and there are even instances of people experiencing anaphylaxis to placebos in clinical trials, notes Dr. James Baker, a vaccine expert and founding director of the Mary H. Weiser Food Allergy Center at University of Michigan. He says that with the nurse in Alaska, “she had anaphylaxis. Whether or not it was allergy-based, we don’t yet know.”

With the Pfizer vaccine, “patients should not be deterred and should not worry that there is something unusual going on here,” Baker says. “It certainly doesn’t look like that.”

When getting a brand new vaccine after 10 months of pandemic stress, emotions and anxiety can also be powerful influencers. Based on the reported symptoms and the rapid response to epinephrine, especially in the Alaskan woman’s case, Saff says these do appear to have been allergic reactions. But that nurse had no history of allergies, and in the two U.K. health-care cases, one person has food allergies, and the other a medication allergy. So there doesn’t seem to be a strong thread linking them.

With the widespread reporting of these early reactions, many people may be especially attuned to symptoms like a flushed face or racing heart, Saff says.

“Everyone who has reacted has responded to the medications, and they got the treatment they needed right away,” Saff says. “I hope these reports don’t deter our patients with food allergies, drug allergies, environmental allergies or asthma from getting the vaccine, given what we know about COVID.”

And never before has a vaccine received this level of public scrutiny, notes Vickery. “This is the first social media pandemic. We are experiencing this incredibly disruptive global event, during a time when access to information is unprecedented and rapid.” Among the first few reports of reactions, “those relatively isolated events circulated very quickly and come to the forefront of people’s consciousness in a way they wouldn’t have before.”