A Johnson & Johnson logo is seen in this photo image in front of a medical syringe and vial of coronavirus vaccine.
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Headache, fatigue, and muscle pain were some of the most common side effects in people who received Johnson & Johnson's one-shot coronavirus vaccine in clinical trials, according to a report by the U.S. Food and Drug Administration released Wednesday.
In the report, FDA staff endorsed J & J's one-shot coronavirus vaccine for emergency approval. If approved, it will be the third vaccine to be approved in the US after Pfizer-BioNTech and Moderna.
Post-vaccination side effects are common, doctors say, and usually signs that they are helping to protect against the disease. The FDA determined that the clinical trial results and safety data "are in accordance with the recommendations in the FDA guidelines on emergency approval of vaccines to prevent COVID-19."
The most common, least severe, "local" side effect among those vaccinated was injection site pain, which was reported by nearly half of vaccine recipients compared with around 17% in the placebo group. Skin redness or erythema and swelling were reported less frequently, the FDA said.
The most common "systemic" side effects, typically less common than local reactions but slightly more serious, were headache and fatigue, according to the report. Almost 40% of people who received the vaccine said they had a headache, and just over 38% said they felt tired.
More than 33% of people vaccinated said they had muscle pain, around 14% reported nausea, and under 10% had a fever, according to the report. Most of the side effects were reported in younger people ages 18 to 59, according to the FDA, although most age groups reported similar nausea rates.
The report found a "balanced" number of cases of Bell Palsy, a condition in which half of your face falls off. The FDA previously announced that the condition would be monitored in recipients of other vaccines and noted that this isn't necessarily a side effect, but it's worth looking out for.
J&J first submitted its Covid vaccine data to the FDA on February 4th. While the vaccine's level of protection varied by region, the company said the vaccine prevented 100% of hospital admissions and deaths.
– CNBC's Berkeley Lovelace Jr. contributed to this report.