If you’ve had COVID, your first vaccine dose may cause worse side effects. Here’s why

Katie Camero
·4 min read

It’s a tale as old as time, or at least as old as the nation’s first coronavirus shot — side effects after COVID-19 vaccination are normal and a sign your body is building a defense against the disease.

The reaction makes sense, experts say, given your body is exposed to a portion of a shiny new germ never before seen in humans. But how does the side effect experience compare for those who already had COVID-19?

Early studies and countless personal stories show previous infection with the coronavirus may open the floodgates for more intense reactions to the first dose of a COVID-19 vaccine, as opposed to the second, which the majority say causes stronger side effects.

Although it seems like an unfair price to pay after already having dealt with an infection, intense reactions after one shot are a minor inconvenience that research shows offers more protective antibodies compared to those with no COVID-19 history.

And they shouldn’t last more than three days. COVID-19, on the other hand, can last weeks and even months for some.

That’s because the first vaccine dose — or single shot of the Johnson & Johnson vaccine — works as a booster to the lessons already learned from natural infection, which may carry with it inflammatory responses such as fevers, chills, headaches and muscle aches.

For some, reactions to the vaccine were on par or worse than their bout with COVID-19.

After receiving his first dose of a coronavirus vaccine, Mike Christensen of Georgia told WSB-TV he woke up with a headache and fever that lasted about 24 hours.

“The highest my fever got was 102.4. And the highest fever I had when I actually had COVID was 100.5,” Christensen said. “So it was a higher fever. It felt like I had COVID again.”

Dr. Susan Malinowski, an ophthalmologist in Michigan who had COVID-19 in March, told The New York Times she was “miserable in bed” for two days after she got her first shot of the Moderna vaccine.

“I had fevers. I had chills. I had night sweats. I had pain everywhere in my body,” Malinowski said. “I was actually more ill after the vaccine than I was with Covid.”

A small, non-peer reviewed study posted in February found that among 231 people who were vaccinated with either the Pfizer or Moderna shot, those who had been previously infected with the coronavirus (83) experienced side effects such as fatigue, headache, chills and fever “with a significantly higher frequency” after their first shot than those with no infection history.

The researchers from the Icahn School of Medicine at Mount Sinai New York said these more intense reactions were similar to those usually felt after second doses.

“The immune system, when you have COVID, creates antibodies. Those antibodies are there to help fight infection. So, when you get the COVID jab, you’re introducing viral particles back into an immune system that already recognizes COVID,” Dr. J’Patrick Fahn, the critical care medical director at CHI St. Alexius in North Dakota who was not involved in the study, told KFYR. “So, your body’s just doing what it wants to do naturally — and that’s fight the infection.”

Other research has shown that people with COVID-19 histories also produce more antibodies after their first shot compared to people without a prior infection.

One study found that a group of 59 health care workers in Maryland with a previous coronavirus infection had higher levels of antibodies after a single dose of either the Pfizer or Moderna vaccine than those without a history of infection.

A separate study in London found that health care workers who did not previously have COVID-19 gained “comparable” levels of antibodies after their first dose of the Pfizer shot to those in recovered COVID-19 patients who had not been vaccinated.

And among those with a previous infection, their antibody levels jumped more than 140-fold after one dose.

Another non-peer reviewed paper posted in February found that one dose of the Pfizer or Moderna shot increased the amount of antibodies in the blood of people who previously had COVID-19 1,000-fold against the original coronavirus stain, the one from South Africa and even the coronavirus that caused the SARS epidemic in 2003.

But everyone’s immune systems are different. So, just because someone experiences intense side effects after their first vaccine dose does not suggest they already had COVID-19. And no side effects after either dose does not mean the vaccine isn’t working.

“It’s really just kind of a reflection of how unique each of our systems are, what other immunities we have,” Dr. Mark Loafman, chair of family and community medicine for Cook County Health in Illinois, told NBC 5. “Each of our immune systems is a mosaic composite of all that we’ve been through and all that we have and all we’ve recently been dealing with.”

“Our individual response varies,” Loafman said, but everybody experiences an “appropriate immune response” for their own body.

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