During the trial, researchers with Johnson & Johnson randomly assigned 805 participants to receive a high or low dose of the vaccine—which is called Ad26.COV2.S—or a placebo. The researchers studied two age groups during this trial: healthy adults between the ages of 18 and 55 and those 65 and older. According to the study, 90 percent or more of all participants had neutralizing antibodies 29 days after getting vaccinated, and 100 percent had antibodies 57 days after getting their vaccine. And while the excitement over the potential of getting your COVID vaccination done in just one shot is warranted, just like any other vaccination, you should expect some potential side effects. According to the study, there are five common side effects that may come from the new Johnson & Johnson COVID vaccine—which interestingly enough, were more largely common among those 18 to 55 than those 65 and older. Keep reading to find out what they are, and for more on vaccines, know that If You Take These OTC Meds, You Have to Stop Before Getting the Vaccine. Read the original article on Best Life. In trial participants ages 18 to 55, a fever was reported as a side effect for 20 percent of those who received a low dose and 48 percent of those who received a high dose. Among those 65 and older, only 4 percent of low-dose recipients and 10 percent of high-dose recipients reported experiencing a fever. “All cases of fever occurred within 2 days after immunization and resolved within 1 or 2 days,” the researchers noted in their study. And for symptoms you may experience from the virus itself, find out The Earliest Signs You Have COVID, According to Johns Hopkins. Among Johnson & Johnson trial participants who received a low dose of the vaccine, nearly 45 percent of those 18 to 55 and nearly 30 percent of those 65 and older reported fatigue as a side effect. For those ages 18 to 55 who received the higher dose, around 70 percent experienced fatigue. And for those 65 and older with a high dose, 40 percent had this reaction. And for more on fatigue, beware that If You Feel Tired After This, You May Have Had COVID.ae0fcc31ae342fd3a1346ebb1f342fcb For Johnson & Johnson study subjects between 18 and 55, around 45 percent in the low-dose group reported having a headache and 70 percent in the high-dose group experienced the same. A headache was less common in those 65 and older. For those in this age group who received a low dose of the Johnson & Johnson vaccine, only around 25 percent had this side effect, and it was reported by nearly 35 percent of those who got a high dose. And for more up-to-date information, sign up for our daily newsletter. Muscles aches, otherwise known as myalgia, were reported by 40 percent of those ages 18 to 55 who only received a low dose of the Johnson & Johnson vaccine. For those 65 and older who received a low dose, 20 percent reported myalgia. As for those who received the higher dose, around 60 percent of 18 to 55 year olds reported this side effect and 25 percent of those 65 and older experienced it, as well. And for more coronavirus concerns, discover why This COVID Protection Measure Is “Not Working,” Doctor Warns. Out of the three local adverse events studied—rashes, pain, and swelling—only pain appeared to be a common reaction among participants in the Johnson & Johnson vaccine trial. For those 18 to 55, nearly 65 percent of those who received a low dose reported pain at the injection site and around 75 percent of those who received a high dose did too. And among those 65 and older, both 40 percent of those who received the low dose and the high dose had pain at the injection site. And for more on the pandemic, take a look at The 3 Things That Could Prevent Almost All COVID Cases, Study Finds.