Three patients taking part in clinical trials for Moderna's (MRNA -1.75%) coronavirus vaccine candidate and two taking part in Pfizer's (PFE -1.82%) study have experienced intense side effects, according to a report published by CNBC. Those effects included high fever, pounding headaches, intense chills, and exhaustion.

The CNBC article identified one of the participants in the Moderna study, a man named Luke Hutchison. After being given the second of two COVID-19 vaccine shots during the trial, he said he awoke late at night with chills and a fever. 

Coronavirus container receiving swab.

Image source: Getty Images.

CNBC did not reveal the identities of the four other patients, who asked to remain anonymous, but the news network did say it had verified their participation in the studies through trial documentation. One, a participant in the Pfizer study, experienced similar side effects to Hutchison after being administered the second dose of the pharmaceutical giant's two-dose candidate.

On a more positive note, all three Moderna trial participants and one in the Pfizer trial reported that their side effects, while intense, melted away after at most one day. All five, meanwhile, expressed the belief that the discomfort they experienced will be worth it for the value of the research being undertaken. Both of the trials in question are phase 3 studies that have tens of thousands of participants. And because they are double-blind, neither the patients nor the medical workers inoculating them know whether any given individual is getting the vaccine or a placebo.

Pfizer -- along with BioNTech (BNTX -0.61%), the Germany-based biotech it is partnering with -- and Moderna are considered by many to be among the front-runners in the race to bring a coronavirus vaccine to market. Both Pfizer/BioNTech's BNT162b2 and Moderna's MRNA-1273 are messenger RNA-based candidates that have been developed relatively quickly, and are now in late-stage testing.

For now, however, no COVID-19 vaccine has completed a full series of clinical trials and reported data sufficient to warrant calling it a success, nor have any candidates been approved by a major regulator.

Moderna, Pfizer, and BioNTech have not yet commented on the CNBC report.