5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers

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5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers
Ian Haydon was one of the first people to try out Moderna's COVID-19 vaccine, as part of the company's phase 1 trial, with first and second doses administered in April and May of 2020.Ian Haydon
  • COVID-19 vaccines may come with some temporary and uncomfortable side effects.
  • Some of the most common include arm pain, flu-like symptoms, and a red rash.
  • Most of these symptoms fade away after a day or so, but the rash can linger for about a week.
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After receiving her second shot of Moderna's COVID-19 vaccine, Susan Ladov hardly slept a wink.

"I spent the night waking up about every hour, hour and a half," the 74 year-old from New Jersey said. "When I got up out of bed, I just felt very shaky and chilled."

Her 75 year-old husband, who had gotten the same second shot about a week earlier, said he felt nothing day-of and then mild arm soreness the next.

This wide range of short-term second dose side effects is common across age groups and vaccine brands.

At best, vaccine-takers may experience just a hint of arm pain. At worst, the day after shot number two can feel like a full-blown flu with nausea, vomiting, and body aches.

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Though they're not life-threatening, it's important to be prepared physically and mentally for these side effects. That may mean taking at least a day off from work, if possible.

Vaccine reactions are common, but temporary

5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers
On March 1, 2021, a woman receives a COVID-19 vaccine at a newly-opened vaccination site in Los Angeles, California.Al Seib / Los Angeles Times via Getty Images

During the first month of COVID-19 vaccinations across the US, 13 million doses were given, according to the CDC. No one in the US is required to report how they feel after a vaccination, but among nearly 7,000 volunteers who shared their side effects with the CDC that month, most noted some arm pain. After that, headaches, fatigue, and dizziness were the most common complaints.

All of this temporary pain is working towards one goal: getting your body ready to stand up to the coronavirus.

Professor Akiko Iwasaki, who studies viruses at Yale, says this process happens in two ways.

First, there is the innate immune response, which happens almost immediately. Second, there is an adaptive immune response, which can take a little longer to present. The initial, innate immune response is often why people get arm pain at the injection site.

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"When these things are being taken up into a cell, they really trigger sensors that are there to detect viruses," Iwasaki said. "So you might feel sore in the arm, a little fever, these are usual responses to this sort of innate immune activation."

Everyone Insider spoke to for this story said they felt some arm pain after their first shot, ranging from nuisance to severe.

"Washing your hair was kind of hard," 34 year-old infectious disease expert Saskia Popescu said.

5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers
Dr. Saskia Popescu.Dr. Saskia Popescu

Norman Ladov said his arm was sore "for about two or three days" after shot number one.

"At it's worst, it felt like I had gotten punched in the arm," said 30 year-old Ian Haydon, who was one of the first people to try Moderna's shot in the company's phase one clinical trials, nearly a year ago.

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He described it as "just sort of a dull ache."

Others said it was so bad they couldn't sleep on that arm.

With Moderna's shot, there's also the possibility for redness, itchiness, and puffiness in the arm where the vaccine was injected. That's what happened to Susan Ladov after shot number two.

"My whole upper arm got very red and somewhat hot and swollen," she said. "My entire bicep area was enflamed."

Plan to rest after the second shot, or the first if you've already had the coronavirus

5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers
Haydon tested out a second vaccine dose that was more than double strength. The side effects that night were "pretty miserable," he said.Ian Haydon

By and large, the most debilitating reports of vaccine side effects come after the second dose of the two-dose shots. Johnson & Johnson's vaccine, which is just one shot, tends to have milder side effects, with arm pain being the most common.

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After shot number two from Pfizer or Moderna, many people feel an all-over malaise, with chills, potential for fever, and body aches. At its worst, the period beginning six to 12 hours after the shot is injected can feel like a bad flu, and last about a day or so.

"This is a sign that your immune system is working, because you develop a much worse response the second time, based on these antibodies and T-cells that are detecting the viral antigen and attacking your own cells," Iwasaki said.

Because the first shot is on board, the body is primed to recognize and fight against the virus's proteins when it sees them again.

"That's the reason why the second dose is much more reactive, because you now have innate and adaptive immune response against the vaccine," Iwasaki said.

It's also the reason why people who have had the coronavirus before might have a more intense reaction to their first shot, similar to how other people feel after the second.

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Popescu said she "just woke up and felt like crap" the morning after her second Pfizer shot.

"Plan on the next day being a little rough," was her advice to others who are going in for their second injection of Pfizer or Moderna's vaccine.

Others said knowing the discomfort could happen, and keeping in mind the end game, really helped.

"I was having trouble keeping track of the big picture when I was feeling so sick," Susan Ladov said. "And my husband just kind of kept reminding me that when this is all done, I'm going to have really good immunity."

35-year-old Jes Adams, who has several medical conditions and tends to react strongly to vaccinations, said before going in for her second shot of Moderna's vaccine "I just kind of communicated with my boss what was going on, and the potential for me to not feel well afterwards."

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That was smart, because the night after her vaccination included vomiting, dizziness, spending much of the next day in bed.

Popescu says people need to be supported by their employers in order to take this time to rest.

"It's really important that people be able to take that time off," she said. "If we're encouraging vaccines, we need to be able to ensure that if they do have a day or two afterwards where they really feel crummy, that they're able to stay home."

It takes at least a month for vaccine protection to ramp up

5 people share their Pfizer and Moderna vaccine side effects, from arm pain to aches and fevers
Seven-year-old Jacquie Carney runs to hug her grandma, Donna Vidrine, upon arrival in Los Angeles, California on November 23, 2020.Allen J. Schaben/Los Angeles Times/Getty Images

Once you've begun vaccination, it takes at least a month for the protection to become robust. In the case of Pfizer and Moderna's shots, full vaccine efficacy is achieved a week or two after the second shot, while for J&J's one shot vaccine, it's 28 days after the jab.

Social distancing and mask-wearing still remain important after vaccination. But according to new CDC guidelines, it's OK for fully vaccinated people to mingle with each other indoors and maskless once they've achieved full protection.

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Fully-vaccinated grandparents can also safely hug unvaccinated grandkids again without masks, though the CDC stresses that maskless, indoor visits should be limited to include one unvaccinated household at a time, and only if the unvaccinated family members present are "at low risk for severe COVID-19."

In addition to allowing for this new brand of safer socializing, vaccination also tends to give people a sense of palpable relief.

"The bottom line is: I'm a mom, I don't want to get sick and I don't want to be one of the unlucky ones that doesn't make it through this," Adams said. "So I went from taking zero chances to being able to do basic things and walk next to people and not be concerned about who they'd been exposing themselves to."

For the Ladovs, a completed vaccination course means being able to have lunch dates again with their fully-vaccinated friends.

In May, they plan to get on a plane and finally see their grandkids in Texas, who "we've seen a lot on video," Norman Ladov said, but haven't been face to face with in more than a year.

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