Unexpected Side Effects of COVID Vaccination

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

Feelings of relief

Multiple studies include feelings of joy, relief, and gratitude on the list of possible side effects of vaccines for most COVID vaccines. Essentially, the idea of ​​finally having some level of protection against the virus caused immediate and dramatic mood boosts in some people.

While uncommon, it was more common than some people might think, averaging about 5% across multiple studies.

woman outside relieved Cesar Okada / Getty Images

To sweat

One of the more typical side effects that people experience after receiving the vaccination is excessive sweating. According to nasty reportsbetween 10% and 20% of people start to sweat after the injection.

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

woman feels overheated with hand fan fizkes / Getty Images

stuffy nose

Our bodies often experience inflammation after receiving a vaccine. However, the swelling that occurs after the COVID injections sometimes causes a unique response – nasal shortness of breath† Inflammation in that region also gave some people runny noses. Although very rare, there have also been some cases of nosebleeds.

Sick man blowing his nose Paul Bradbury / Getty Images

Changes in the menstrual cycle

A study from Obstetrics and Gynecology found that women who received one dose of a COVID-19 vaccine during their menstrual cycle extended their cycle by nearly a day compared 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 can affect symptoms of the menstrual cycle, such as pain, mood swings, or flooding.

Woman uses 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 still occur in a small percentage of people. Hives, itchy skin and eczema occurred in a few individuals, but the most unexpected side effect – swelling of the lips – was much rarer and occurred in only one person from about 800 participants in the study

Young woman examining lips Dmitry Ageev/EyeEm/Getty Images

Digestive Problems

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

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

man feels nauseous outdoors klebercordeiro / Getty Images

Urgent need to urinate

In addition to gastrointestinal problems, studies also identified some urinary symptoms, the most common of which is a urgently need to pee† A few people also report going to the bathroom more often at night. One person said they had trouble urinating after receiving the vaccine.

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

Woman with paper sitting on toilet bowl Kittisak Jirasittichai / EyeEm / Getty Images

Temperature intolerance:

Temperature changes after vaccination are not uncommon. As the immune system begins to form antibodies to fight possible infections, many people may feel hot or have chills. However, the COVID vaccines can sometimes influence the endocrine systemcausing a few people to become sensitive or intolerant to hot or cold temperatures.

Man feels very cold at home with warm clothes tomaso79 / Getty Images


Of the side effects of the vaccine, one of the most serious is swelling of the heart muscle, called myocarditis. This mainly affects young men who receive one of the mRNA vaccines. Most commonly, myocarditis causes shortness of breath, chest pain, and fatigue. Severe myocarditis can weaken the heart and restrict blood flow, leading to a heart attack or stroke.

However, all in all important reported cases of vaccine-related myocarditis, symptoms resolved within days and no complications occurred.

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


The AstraZeneca vaccine uses an adenovirus vector instead of mRNA technology like the Moderna and Pfizer-BioNTech vaccines. Because of this, side effects vary slightly in comparison. One of the rarer, more serious side effects is: thrombocytopenia or a low platelet count. If the platelet count falls too low, internal bleeding can occur and the condition is sometimes fatal.

Blood sample for platelet count
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