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Patients in clinical trials are usually faceless. But as the experimental Covid-19 vaccine being developed by Moderna Therapeutics has begun advancing through studies, it has found a much more visible advocate: trial volunteer Ian Haydon, a 29-year-old in Seattle.

Haydon has spoken about the vaccine on CNN and CNBC. He even said he’d volunteer to be exposed to the novel coronavirus, SARS-CoV-2, if researchers want to test to see if the vaccine was actually effective. But up until now he has left out a key detail: He is, apparently, one of three people in the trial who had a systemic adverse reaction to the vaccine. 

Twelve hours after receiving his second dose, he developed a fever of more than 103 degrees, sought medical attention, and, after being released from an urgent care facility, fainted in his home. He recovered within a day.


He has not brought up the side effects previously, he said, out of “an abundance of caution.”

“I understand that sharing the story, it’s going to be frightening to some people,” he said. “I hope that it doesn’t fuel any sort of general antagonism towards vaccines in general or towards even this vaccine.”


But he decided to speak now because he hopes his story counterbalances the desperation that some people feel to push a vaccine to market regardless of the consequences. Haydon points out that the whole purpose of the study he was in, known as a Phase 1 clinical trial, is to find the right dose of the vaccine going forward. That means to find a dose that causes the body to produce antibodies, but does not result in too many side effects.

“As we rush to get a vaccine developed as quickly as possible, the reality of vaccine development is that it can only be rushed so much and the trial still needs to take place,” Haydon said. “They have to move at the speed they move at. And stories like what happened to me, they matter because they shape the approval process.”

In the 45-person Moderna study, four participants experienced what are known as “Grade 3” adverse events — side effects that are severe or medically significant but not immediately life-threatening. Neither the company nor the National Institute of Allergy and Infectious Diseases, which is running the trial, have previously detailed the nature of those incidents, but Moderna did disclose that three, likely including Haydon, received the highest dose of the vaccine that was tested, and had reactions that involved their whole bodies. A fourth received a lower dose and had a rash at the injection site. 

Such side effects are “noteworthy, but it doesn’t stop the train,” said William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center. The goal of studies is to establish a threshold at which something might go wrong.

With drugs, Schaffner said, patients tolerate the risk of side effects because they want to get better. “In contrast,” Schaffner said, “we give vaccines to healthy people in anticipation that they might contact the germ, the virus, down the road. But because we give them to healthy people, actually our standards for safety are higher than they are for drugs.” 

In Haydon’s words: “The point of the Phase 1 trial is to look out for health problems.” He said he received great medical care, and though he felt more sick than he ever has before, he was never afraid for his long-term health. “I don’t regret the decision I made to enroll in this study.”

Haydon, a communications manager at a university, initially found out about the study, which was being run in Seattle, from a colleague who sent him a link. He, along with thousands of other people, applied. They called him 11 days after he applied.

He went to the trial site for a physical, and signed a 20-page consent form. The vaccine, it told him, could conceivably cause severe anaphylactic shock, and there was no way to predict exactly how his immune system would respond to the new vaccine. He’d looked at research on other Moderna experimental vaccines, which work via an entirely new technology that uses messenger RNA, the body’s key envoy of genetic information inside cells, and thought they seemed relatively safe. During the physical, researchers took blood; the lab work came back a week later, and he received his first dose of the vaccine on April 8.

Haydon doesn’t like needles, and was as worried about the blood draw — which uses a bigger needle — than the actual shot. He remembers waiting, and being told that the reason he was waiting was because researchers were giving doses in ascending order, and he was to receive the high dose of the vaccine. But the injection was uneventful. If his eyes were closed, he said, he would not have felt it. He was given a paper log on which to write down any symptoms, a digital thermometer, and a small ruler to measure any reactions at the injection site.

He had arm pain the next day, “like being punched in the arm,” he said, and for a day he had trouble lifting his arm at the shoulder. But within days he was back to normal.

Haydon said he was slightly nervous before the second dose. He knew that second doses were given to increase the immune system’s response, and wondered if he might have more side effects. His arm became sore much more quickly this time. He got home from the clinic at about noon. At around 10 p.m., he started to get chills. He’s normally too hot at night, but he bundled up in sweats. His fingertips felt cold. He fell asleep, but woke up a few hours later with a raging fever.

At 1:30 a.m., his temperature was 103.2 degrees. At 3:45, it was 103 degrees. He was nauseous, and his muscles hurt. 

The clinic where he was vaccinated had given him a 24-hour phone number to call, but he’d been reticent. His girlfriend, with whom he lives, called. They said to go to urgent care. It was a 10-minute drive. They arrived at 5 a.m.

The doctors met him in what looked like space suits. Even though he’d had a vaccine, he was also a potential Covid patient. They took him into an exam room, took a lot of blood, and gave him a nasal swab. He asked them to avoid his left arm, where he’d gotten the vaccine, but they ended up taking blood from both of his arms. His fever had already fallen to 99.8 degrees. They gave him Tylenol. The physician taking care of him offered to try to get him admitted to a neighboring hospital, but he decided to head home.

He and his girlfriend arrived home at 7 a.m., and he slept until noon. His temperature was 101.5. He got up to go to the bathroom, and became so nauseous he threw up. On his way back from the bathroom, he fainted. His girlfriend caught him and kept his head from hitting the floor. 

She then called one of the doctors working in the study, and asked what they should do. The doctor told them he could go back to urgent care, or call 911, and reminded them that all his medical costs would be covered by the study.

But he got to a couch and was given sports drinks. He spent the afternoon there, with a wet towel on his head, fighting the fever. By 9:45 p.m., it was back down to 99.1. It tapered off. He says he felt better within a few days, and has had no side effects since. 

Haydon said the experience left him as sick as he’d ever felt. But standard flu-like symptoms that resolve within a day are not necessarily considered a reason not to use a vaccine that prevents a more serious illness.

Given the stakes of a Covid-19 vaccine, the side effects described in the Moderna release would likely be seen as acceptable even if they turned out to be seen in future studies. The severe effects were only seen at high doses that are not being taken forward. The other vaccine for which early data are available caused fever in almost half of recipients.

But it’s also not clear what will happen as the vaccine moves into larger studies. “Humans have a very diverse immune system,” said Larry Schlesinger, the president and CEO of the Texas Biomedical Research Institute, a nonprofit. “And then you add on top of that diabetes or, you know, age 70 and you can imagine that the immune response will be very, very different.”

The difficulty, Schlesinger said, is that right now we are only getting “tidbits” of information about the new vaccine.

“Tidbits of science are always dangerous for the public to read because they give a false understanding, or a false sense of security, that we’re making progress or not,” Schlesinger said. “And then tomorrow we hear something completely opposite. And before you know it, the credibility of the scientific process is undermined and people stop listening.”

What does he think now? “It’s just not enough information at the current time.” That’s why we need clinical trials — and volunteers like Ian Haydon.

  • Shocked and outraged at all the anti-vax poppycock here. The patient had flu-like symptoms for a couple hours after receiving a high dose of the vaccine. The actual disease can linger for weeks to months and cause far more serious symptoms. I’d get vaccinated ASAP once it’s available, and everyone else should too. In fact, getting vaccinated should be the law, zero exceptions.

    • Are you being paid to write this? I’ll tell you what you get it first and come back to me in 6 months.

    • I am shocked at how stupid people can be. COVID-19 stands for coronavirus disease 2019. What is coronavirus? It is nothing but the common cold.But if you have the president or a public figure or a scientist calling it COVID-19 that makes it sound scary. It’s nothing but the common cold. But now you got people running around snatching up hand sanitizer to kill all the germs on your hands when your body needs those germs. Without normal every day germs your body has nothing to fight to build up an immune system so killing all the germs you have no immunity to anything. Yes and then the common cold can kill you. Scientist have been trying for many years now to come up with a vaccine for the common cold.

  • @Thomas – I’m truly sorry about your son, but I’m not sorry about vaccines.

    Safe never has meant 100% with any medication. Take any RX drug and look at the side effects – even aspirin.

    If someone died or was in the hospital for weeks on a low dosage I would really worry. If the FDA said not to proceed to a phase II or they wanted the Phase I extended with other patients, I would worry.

    That 3 people who took a dose 2-3x higher than what they intend to use got a fever … less of a worry.

    I wonder how many people would be dead because they don’t have a vaccine against polio or the measles. How bad it is for children to contract measles and the outbreaks we had last year because people think it’s so “unsafe” and lower the herd immunity with their non-sense. Those people imo only think about themselves.

    Here is an obvious safety problem – the polio vaccine was produced initially as a live vaccine, an absolute first, some labs mixed up the real live virus and that got people really sick. That didn’t stop the US government from pushing a dead virus variant – if needed 100% safety on everything we did, we would have a lot of deaths.

  • Only foolish people would be involved in this study. Only those who haven’t studied the long-term effects of vaccines. But, to take and experimental vaccine that manipulates our genetic code is insane. What if these people have children? Flue vaccines, in general, rarely work. This vaccine is a giant step into the unknown that could be devastating to generations to come.

    • This vaccine does not “manipulates our genetic cod”
      mRNA is read and spike protein is produced, but after a while it disintegrates. It does not enter nucleus of the cell nor does it integrate itself into your DNA.

  • Herd immunity
    I cant see any other way .
    Chances of a vaccine is 10 percent at best and that’s a two year wait if were very lucky .
    In 3 or 4 years most of us still alive should have some percent of immunity.

  • Vaccines have gone to Phase 2 before, that in no way means it is safe Peter. I have no idea why you would even state such a lie. It is clear you have no medical background. Was the swine flu vaccine in the 70’s safe? It passed all requirements and yet paralyzed more people than swine flu did. We do not need a vaccine. The majority of people recover from coronavirus. 65% of deaths occurred in nursing homes and you can blame leadership for that mistake as many govenors and public health leaders allowed covid-19 positive patients to be sent to nursing homes. This is why so many elderly died. A vaccine injury court exists for a reason and anyone that claims a vaccine is 100% safe is a liar. Every single vaccine insert states the vaccine has never been tested to see if it causes carcinogenic or mutagenic effects. The majority also state they have never been tested to see if they cause infertility. 100% protection is not guaranteed in all either. Next time try reading a vaccine insert before you comment Peter. People could go get this vaccine because of your words and would believe it to be safe. How would you feel if that person then experienced a vaccine injury, something life long, because of listening to your words? Would you even care or was their injury “for the greater good”? My son will forever have a seizure disorder because of the MMR shot, a vaccine that I was told was safe. It wasn’t safe. My son can no longer talk, he will be in a diaper for life, and people like you have the nerve to lie about the risks to others. One day you will have to answer for that mentality just as the people in this field who seem to not care about the oath they took to do no harm.

    • My heart goes out to you. You post will give people much to think about. I don’t think that others had the same reaction BUT one never knows. To be part of this ‘experiment’ just is too risky for some…but how can you know?

    • COVID-19 stands for coronavirus disease 2019. What is coronavirus? The common cold. There is no cure for the common cold. Penicillin doesn’t help with the common cold. are you can do with the common cold is treat the symptoms. Scientists have been trying to come up with a vaccine for the common cold for many years now with no luck.

  • I really wish the media would try to not sensationalize tidbits of information. We should wait for the full results of the trial, have that peered reviewed. Moderna already has permission to go to Phase II, which means the safety of the vaccine is proven. Ian was one of 3 people, all of which were given the highest dose that had a “severe” reaction, he got a fever, felt sick and had to go to the hospital. He wasn’t admitted to the hospital and he is certainly not as sick as 10’s of thousands dying in COVID wards right now. STAT has a bug up their rear-end because Moderna released some good news last week. The author and the publication have made it point to punish Moderna … just look at the headlines! They didn’t even compare those safety results with that of other vaccines that are on the market. This is just piss-poor judgment to highlight this guy and not highlight say the other 42 people in the trial that had no adverse reactions (other than a rash at the injection site which could have been a result of anything, like using the wrong gloves to administer the vaccine). I for one wish I was on the phase 1 trial, you can be absolutely sure I want to be on phase 2. The company was clear that even at the lowest dosages, antibody response is strong. I’ll wait until June 1 when the company explains what they are doing to the scientists.

    • Antibody results were terrible. Less antibodies than if you had had the virus and recovered.way less and they only had that result in 4 of original vollenteers. Which they won’t even give you the number. they tell you 45 and they tell you 60. Which is it?

    • @Philip Cramer What are you saying? That’s gibberish. 8/45 because they were the first to be injected.
      “The first four participants will receive one injection with the low dose, and the next four participants will receive the 100 mcg dose. Investigators will review safety data before vaccinating the remaining participants in the 25 and 100 mcg dose groups and before participants receive their second vaccinations. Another safety review will be conducted before participants are enrolled in the 250 mcg cohort. ”

    • @philip – not true. The release said higher than convalescent serum … we’ll just have to see, but unless you have facts to refute what the company released, you should be quiet. It’s pretty clear we have a LOT of misinformation, propagated by anti-vaxers and irresponsible media like this author that can’t write a balanced objective article … if I was a cynic, I would say it was written to make the stock a buying opportunity …

  • I wonder about the use of adenovirus which causes common cold to use as vector to transport the immunogenec protein. Why ? Because folks with immunity to adenovirus would attack and reject the adenovirus along with immunogenec protein from COVID19. Would the plasma from this vaccinated person have the same effectiveness as convalescent plasma ? If yes, that’s real progress.

    • COVID-19 stands for coronavirus disease 2019. What is coronavirus? The common cold. There is no cure for the common cold. Penicillin doesn’t help with the common cold. are you can do with the common cold is treat the symptoms. Scientists have been trying to come up with a vaccine for the common cold for many years now with no luck.

  • You are trying your best to get the vaccine hopefully you will get to proper one
    What is happening with the MrNa1273?
    South Africa is waiting for you scientific research with patience

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