Aaron Rodgers says he's allergic to the COVID mRNA vaccines. Is that possible?

Green Bay Packers quarterback Aaron Rodgers has been in the hot seat after admitting he was not vaccinated against COVID-19 after testing positive, despite claiming he was "immunized." 

In an interview on "The Pat McAfee Show," Rodgers said he was allergic to an ingredient used in two mRNA vaccines – Pfizer and Moderna – and steered away from the Johnson & Johnson vaccine after reports of adverse reactions. 

In April, the administering of the J&J vaccine was paused after rare, but severe reports of blood clotting in six individuals. It was lifted 11 days later after the Food and Drug Administration and Centers for Disease Control and Prevention determined the benefits of the vaccine outweighed the risks. 

Rodgers did not disclose what ingredient he was allergic to, but noted that the CDC warned those allergic to the polyethylene glycol ingredient should choose another form of protection against the virus.

“Health is not a one size fits all for everybody, and for me, it involved a lot of study in the offseason,” Rodgers said. "My medical team advised me that the danger of an adverse event was greater than the risk of getting COVID and recovering."

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Rodgers, 37, now faces criticism for his reasoning behind not getting vaccinated and his evasiveness regarding his vaccine status prior to testing positive for the virus. 

What Rodgers has said about the COVID vaccine?

On the Pat McAfee show, Rodgers said there was a "witch-hunt" in the NFL for who was vaccinated and who wasn't. 

"At the time, my plan was to say I've been immunized," he said. " It wasn't some sort of ruse or lie, it was the truth."

Rodgers was referencing a press conference in August where a member of the media asked if he was vaccinated and he responded by saying he was "immunized."

He said he was not an anti-vaxer, but a "critical thinker."

"I am not a COVID-denier or any (expletive) like that," Rodgers said. "I just wanted to make the best choice for my body."

The three-time MVP said he was allergic to an ingredient in mRNA vaccines and decided against the Johnson & Johnson shot. He pursued alternative measures to protect himself and used ivermectin, a drug used to treat threadworms, roundworms and other parasites, that has not been approved by the FDA to treat COVID-19.

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Could his vaccine allergy be real?

In short, yes, Rodgers could be allergic to an ingredient in mRNA vaccines. However, he did not disclose a specific ingredient allergy.

One ingredient – polyethylene glycol or PEG – has been hypothesized to be the cause of severe post vaccination allergic reactions. 

A recent study published in the Annals of Allergy, Asthma & Immunology found that not to be true. 

Blanka Kaplan, co-author of the study and specialist in adult and pediatric allergy and immunology from Northwell Health, told USA TODAY they found most people with severe post vaccination allergic symptoms were not caused by a hypersensitivity to PEG. 

Of the 105 participants in the study who had reactions to the first dose of mRNA vaccines, 91 went on to receive their second dose without any severe reactions and some were pre-medicated with allergy medicines.

"If someone is really concerned about an allergic reaction to the vaccine, they should visit a doctor," Kaplan said. "There's a good chance [Rodgers] can get the vaccine and be OK."

How common are allergic reactions to the COVID vaccine?

Allergic reactions to COVID vaccines are rare.

According to the CDC, anaphylaxis – a severe and possible life-threatening allergic reaction – occurs in 2 to 5 people per million vaccinated in the United States.

Thrombosis with thrombocytopenia syndrome or TTS is also a rare reaction after taking the Johnson & Johnson vaccine. As of Oct. 27, the CDC and FDA identified 48 confirmed reports of people who got the J&J vaccine and later developed TTS of the over 15.5 million doses given in the U.S., according to the CDC.

COVID vaccines have been deemed safe and effective and were recently approved by the FDA and CDC for children aged 5 to 11.

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Follow reporter Asha Gilbert @Coastalasha. Email: agilbert@usatoday.com.