One COVID-19 vaccine trial volunteer in the U.S. described the side effects he experienced.
However, experts assure that flu-like symptoms is a normal reaction after receiving the treatment.
Kim Jae-hee has the full story.
With Moderna's vaccine showing around a 94-percent efficacy rate, many people actually volunteered to be injected with the vaccine during its trial process.
But fears of side effects rise, after one trial participant said on CNN that he developed a low-grade fever, had fatigue, chills, stiffness, and muscle soreness in his left arm, as if he had been punched, before feeling better the next day.
Amid rising concerns, Britain said on Thursday that it will compensate any individuals who suffer severe side effects from vaccines, ahead of Pfizer's rollout next week.
But many experts say that slight flu-like symptoms are normal after being vaccinated, as this shows that the body is reacting to the vaccine.
Kelly Moore of the Immunization Action Coalition also offered assurances, saying that having reactions to vaccines just means that they're working, and there's nothing dangerous about it.
Experts also say that any potential side effects which are only temporary should not prevent people from getting vaccinated.
Meanwhile, American IT company, IBM, has warned of hackers potentially targeting companies which are critical in supplying COVID-19 vaccines.
The company said on Thursday that a coordinated, global network of hackers had targeted organizations linked to so-called "cold chain" the process of keeping vaccine doses at extremely low temperatures during their storage and transportation.
The company said that starting September, the hackers had targeted organizations across the globe, including those in Italy, Germany, Czech Republic, Taiwan and even South Korea.
Kim Jae-hee, Arirang News.