Feeling rough after your COVID shot? Congrats, it’s working!

A new study led by researchers at the University of California, San Francisco (UCSF) suggests that the tiredness, muscle and joint pain, chills, headache, fever, and nausea experienced by some after receiving a COVID-19 vaccine may be evidence of a robust immune response. The findings, published online on June 10 in the Annals of Internal Medicine, come at a time when fewer than 1 in 4 people in the United States have received last year’s updated COVID-19 vaccine, despite the virus claiming more than 23,000 American lives this year.

The study analyzed symptom reports and antibody responses from 363 individuals who received the Pfizer-BioNTech or Moderna mRNA vaccines when they were first introduced. The researchers discovered that those who experienced seven or more symptoms after the second dose had nearly double the antibody levels compared to those who did not have symptoms.

Temperature Increase Linked to Higher Antibody Levels

About 40% of the study participants wore a device to monitor their temperature, breathing, and heart rate. The researchers found that those whose skin temperature increased by 1 degree Celsius after the second dose had three times the antibody levels six months later compared to those whose temperature did not increase.

“Generally, we found that the higher the number of side effects, the higher the level of antibodies,” said first author Ethan Dutcher, MD, PhD, a postdoctoral researcher in the UCSF Department of Psychiatry and Behavioral Sciences, and the Weill Institute for Neurosciences. “But this wasn’t a hard rule: some people without side effects had better antibodies than some people with side effects.”

COVID’s Lingering Impact and the Importance of Vaccination

As the virus has evolved and fatality rates have fallen, many people are underestimating its impact. “The toll of COVID is still high for some – sickness, lost work, lasting fatigue and the dreaded long COVID,” said co-senior author Elissa Epel, PhD, a vice chair in the UCSF Department of Psychiatry and Behavioral Sciences. “While the symptoms from vaccination can be very unpleasant, it’s important to remember that they don’t come close to the disease’s potential complications,” she said.

“With COVID-19 vaccines likely here to stay, identifying what predicts a strong antibody response will remain important,” said co-senior author Aric Prather, PhD, professor in the UCSF Department of Psychiatry and Behavioral Sciences.

The latest recommendations from the Centers for Disease Control and Prevention are that everyone 6 months and older should receive the updated vaccine, and those 65 and older should receive an additional dose.

The study’s findings provide a new perspective on the side effects experienced by some after receiving a COVID-19 vaccine. While the symptoms may be unpleasant, they may also be a sign that the vaccine is working as intended, stimulating a strong immune response that could help protect against future infections. As the world continues to grapple with the ongoing pandemic, understanding the factors that contribute to a robust antibody response will remain crucial in the fight against COVID-19.

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