Many studies have confirmed the efficacy and safety of the new COVID-19 vaccines. However, as with any medication, there are some side effects. Most are common and occur with any type of injection — pain, muscle soreness, and fatigue. However, studies have uncovered a few that are much more unexpected.

Feelings of Relief

Several studies include feelings of joy, relief, and gratitude among the list of potential vaccine side effects for most of the COVID vaccines. Essentially, the idea of finally having a level of protection against the virus caused immediate and dramatic mood boosts in some people.

While uncommon, it did occur more than some people might think, averaging around 5% across multiple studies.

woman relieved outdoors Cesar Okada / Getty Images



One of the more typical side effects that people experience after receiving the vaccination is excess sweating. According to reports, between 10% and 20% of people start sweating following the shot.

Heating up is part of the body’s natural immune response, and this side effect is simply an attempt to cool down and is not generally a sign of any major issue.

woman feel overheated using hand fan fizkes / Getty Images


Nasal Stuffiness

Our bodies often experience inflammation after receiving a vaccine. However, the swelling that occurs following the COVID shots sometimes causes a unique reaction — nasal stuffiness. Inflammation in that region also gave some people runny noses. While very rare, there have been some case reports of nosebleeds, as well.

Sick man blowing his nose Paul Bradbury / Getty Images


Menstrual Cycle Changes

A study from Obstetrics & Gynecology discovered that females who received one dose of a COVID-19 vaccine during their menstrual cycle extended their cycles by nearly one day in comparison to unvaccinated people.

Experts pointed out that menstrual cycles naturally vary in length from month to month and that this change is extremely minor. However, this small change indicates that the vaccines could influence symptoms of the menstrual cycle, like pain, mood changes, or heaviness of flow.

Female using menstrual calendar app on mobile phone grinvalds / Getty Images


Lip Swelling

According to research findings, allergic reactions to the COVID vaccines are quite rare, but they do still occur in a small percentage of people. Hives, itchy skin, and eczema affected a few individuals, but the most unexpected side effect — lip swelling — was much rarer and occurred in only one person from over 800 participants of the study.

Young Woman Examining Lips Dmitry Ageev / EyeEm / Getty Images


Digestive Issues

A notable number of people develop gastrointestinal symptoms after their vaccinations. Of these, reports of nausea were the most numerous. Diarrhea is usually the most prominent, after nausea, but is around three times rarer.

Research into the Pfizer-BioNTech vaccine found that a few people lost their appetites for several days, though a small percentage reported feeling hungrier after the vaccine.

man feeling nausea outdoors klebercordeiro / Getty Images


Urgent Need to Urinate

Beyond gastrointestinal issues, studies also identified a few urinary symptoms, the most common of which was an urgent need to urinate. A few people also report having more frequent trips to the bathroom at night. One person said they had difficulty urinating after receiving the vaccine.

These side effects typically occurred in less than 1% of the tested population.

Woman With Paper Sitting On Toilet Bowl Kittisak Jirasittichai / EyeEm / Getty Images


Temperature Intolerance

Temperature changes following vaccination are not uncommon. As the immune system begins forming antibodies to fight off potential infection, many people may feel hot or have chills. However, the COVID vaccines can sometimes affect the endocrine system, causing a few people to become sensitive or intolerant to hot or cold temperatures.

Man feeling very cold at home with warm clothes tommaso79 / Getty Images



Of the vaccine side effects, one of the more serious is swelling of the heart muscle, called myocarditis. This primarily affects young males who receive one of the mRNA vaccines. Usually, myocarditis causes shortness of breath, chest pain, and fatigue. Severe myocarditis can weaken the heart and limit blood flow, leading to a heart attack or stroke.

However, in all major reported cases of vaccine-related myocarditis, symptoms resolved within several days and no complications developed.

man holding his chest in pain indoors. ljubaphoto / Getty Images



The AstraZeneca vaccine uses an adenovirus vector, rather than mRNA technology like the Moderna and Pfizer-BioNTech vaccines. Because of this, its side effects vary slightly in comparison. One of the rarer, more serious side effects is thrombocytopenia or low blood platelet counts. If platelet counts fall too low, internal bleeding may occur and the condition is sometimes fatal.

Blood sample for platelet count


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