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All You Need to Know About Vaccine Side Effect


In the last decade, over 1 billion children have been vaccinated. Back in 2019, around 85% of newborns got 3 doses of the DTP3 (diphtheria-tetanus-pertussis) vaccine, protecting them from a serious disease, disability, and even death. Right now, immunization is preventing 4 to 5 million deaths annually.

The truth is, vaccines have spiked debates for a very long time. They are often the reason you are stuck in an awkward conversation with someone who doesn’t share the same view as you when it comes to vaccinations.

Yes, there will always be some level of fear and uncertainty. But, to understand the sheer impact of vaccination, it is crucial to take a look at all aspects that are surrounding it—even the bad ones. Just like any medication or a chemically manufactured product out there, vaccines can cause adverse effects.

Although, for the most part, they are minor, people are worried they could affect the quality of life. That’s why we decided to compile this comprehensive guide on vaccines and side effects. They will give you that valuable insight that you’ve been looking for.

What Are the Possible Side Effects?

COVID Vaccine

After receiving a vaccine, patients normally experience temporary side effects. They could last anywhere from a couple of hours to a few days after a dose. This is completely normal since it’s the body’s natural response system that’s reacting to the chemicals in the product.

The system is doing its best to create immunity to battle the disease. This is what experts refer to as a reaction or an inflammatory response. It is not uncommon for these reactions to get in the way of your daily life. Sometimes, you would need to take over-the-counter meds to cope with the aches or fever.

These typical adverse effects may include:

  • Reactions on the injected area. They are typically associated with swelling, redness, and pain.
  • Flu is accompanied by mild fever, muscle pain, chills, exhaustion, joint pain, or a headache.
  • Allergic reactions. When a patient is allergic to any of the products inside the vaccine, the body can react abnormally. It can result in swelling, rash, elevated heart rate, decreased blood pressure, vomiting, etc.

Do have in mind that side effects are also classified by the severity of impact. There are mild to moderate and moderate to severe problems. Mild side effects are the ones that cause mild rash, tenderness, swelling, or fever. Whereas the more complex ones can cause a bad rash, severe infection, and a weakened immune system.

Why Vaccines Have Side Effects?

Every day, our body is fighting external agents that are trying to invade our system. The cells, however, develop a memory of these invading pathogens. Therefore, the immune system becomes capable of recognizing the external agent.

These memory cells have one job – spot the virus that invaded the system and get the immune system to attack it. Vaccines are basically tools for these memory cells. So, when they enter the system, the body can fight it. There is always a chance that the patient’s body won’t react favorably to a vaccine. That’s because everyone is different, and their body reacts differently to the vaccine.

Then, there are stress-related reactions. When someone is very anxious about getting a vaccine, they can turn pale or start to sweat. They can feel lightheaded, their breathing pattern will start to speed up, and they could lose their sensations in the feet, hands, or face. These reactions, however, are not caused by the vaccine. They are triggered by the stress from getting one. When the patient calms down, these reactions disappear.

What Should People Do When Facing These Side Effects?

If you develop any of these reactions or effects, it is best to consult with a healthcare provider. To prevent the side effects from turning into an actual problem, it is best to sit in the hospital for at least 15 to 30 min post-vaccination to see how the system will react to it. For example, you can sit in your vehicle for a little while before you drive off. This can be a worthwhile strategy.

Those who develop injection site pain or fever typically take over-the-counter treatments. Like paracetamol, aspirin, or ibuprofen. Others like to rely on home remedies for relief. Such as a cold compress to relieve the stiffness and pain. If you are not feeling too well, it is crucial to drink plenty of fluids. This can help you avoid dehydration and ease the discomfort. 

Different Vaccines May Cause Different Side Effects

Not every vaccine has the exact same side effects. Each immunization provider ensures a unique impact on the human body. But, to understand the impact, it is important to take a look at each individualized side effect of a vaccine. The table below will give you a general outline.


Effect of illness​

Vaccine side effect​

Hepatitis A

Around 7 in 10 adults experience nausea, vomiting, fever, jaundice, tiredness, liver pain, etc.

Roughly 1 in 5 patients develop local swelling on the injected area. Serious reactions are very rare. 

Hepatitis B

An estimated 1 in 4 chronic carriers experiences liver cancer.

Anaphylaxis happens in 1 in 1 million people. While 2 in 100 develop a fever. Around 1 in 20 have local swelling. 


Around 1 in 15 children affected with measles experience pneumonia. 1 in 1000 develop brain inflammation. Some could experience permanent brain damage. 

Roughly 1 in 10 develop redness, pain, and swelling on the injected area. 1 in 20 have a non-infectious rash. 

Final Thoughts

As you can see, the sheer impact and benefit of any vaccine outweigh the possible side effects. Although there will always be a risk when taking chemical products, vaccines are a worthwhile choice. Not only to protect yourself but those around you as well. This is the kind of protective strategy everyone is looking for.


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Everything You Need to Know about COVID-19 Vaccines

The arrival of COVID-19 vaccines was much-anticipated as the number of new cases and deaths kept rising in the United States and across the globe. Today the immunization process is going strong, which is why it’s important to learn as much as possible about the approved vaccines, how they work, and their effectiveness and potential side effects. Read on to get informed about Pfizer-BioNTech, Moderna, Astra Zeneca, and Janssen (Johnson & Johnson) vaccines.

Overview of manufacturers


Pfizer is a well-known American pharmaceutical giant founded in 1849. Headquartered in Manhattan, Pfizer develops medications and vaccines for a wide range of medical conditions and fields ranging from oncology to immunology.

BioNTech, on the other hand, is a German biotechnology company founded in 2008. The Mainz-based company combines groundbreaking research with cutting-edge technology to develop therapeutics.


Based in Cambridge, Massachusetts, Moderna was founded in September 2010. The pharmaceutical and biotechnology company focuses primarily on drug discovery and development and mRNA-based vaccine technologies. Their pipeline includes 24 development programs, 13 of which entered clinical studies.

Johnson & Johnson (Janssen)

Breaking: Johnson & Johnson vaccine had been paused over rare blood clots since this week.

Johnson & Johnson, founded in 1886, develops pharmaceuticals, medical devices, and consumer packaged goods. As one of the most well-known American companies, Johnson & Johnson has become the world’s largest and most broadly-based healthcare company focused on creating healthier communities. Janssen is a Belgium-based pharmaceutical company owned by Johnson & Johnson.


Founded in April 1999, AstraZeneca is a British-Swedish biotechnology and pharmaceutical company headquartered in Cambridge, England. Their pipeline includes 174 projects. In April 2020, AstraZeneca announced a collaboration with Oxford focused on the development and distribution of the COVID-19 vaccine.

Vaccines overview

There are different types of COVID-19 vaccines in terms of mechanism of action. These four vaccines belong to two categories: mRNA and viral vector (adenovirus) vaccines. Below, you can learn more about each vaccine and how it works.


Pfizer and BioNTech’s BNT162b2 vaccine is a messenger RNA (mRNA) type of vaccine. Messenger RNA is a genetic material the cells in the body read to make proteins. The vaccine relies on genetically engineered mRNA to give cells instructions on how to produce a harmless segment of S protein found on the COVID-19 virus surface. Once a person is vaccinated, the immune system starts making the pieces of S proteins that emerge on the surfaces of the cells. 

As a result, the immune system creates antibodies. Therefore, if a person gets infected with the virus, the antibodies will strive to protect them. Upon production of S protein fragments, the mRNA breaks down immediately. In fact, mRNA never reaches the nucleus of a cell where your DNA is stored. The vaccine is administered in two doses given 21 days apart. Each vaccine vial contains 5 doses of 0.3 milliliters.

When was the vaccine issued?

On November 20, 2020, Pfizer requested an emergency use authorization from the FDA. On December 11, 2020, the Food and Drug Agency granted Pfizer-BioNTech vaccine their request. Vaccination in the U.S. started on December 14. The first Western country that approved this vaccine was Great Britain on December 2, but seven days later (on December 9, 2020), Canada did the same. The vaccine was authorized in the European Union on December 21, 2020.

How many people have received the vaccine?

The latest data shows at least 67,56 million doses have been administered so far in the United States. Keep in mind these numbers keep changing by the day as more and more people get vaccinated.

How effective is the vaccine?

According to the latest real-world evidence, two weeks after the second vaccine dose, protection by Pfizer-BioNTech is strong, with 97% effectiveness. In other words, this vaccine has 97% effectiveness against symptomatic COVID-19 cases, hospitalizations, severe and critical hospitalizations, and death. Additionally, the effectiveness of this vaccine is 94% against asymptomatic cases. One of the earlier reports, a trial involving 43,548 participants, reported two doses of this vaccine conferred 95% protection against COVID-19.

Does the vaccine have side effects?

Some people may experience temporary and mild side effects after vaccination with the Pfizer-BioNTech vaccine. These adverse reactions tend to last a few days only and include:

  • Tiredness
  • Fever
  • Chills
  • Headache
  • Pain and swelling around the injection site

Keep in mind these side effects are normal and, actually, indicate the vaccine is doing its job in “activating” the immune system.More serious side effects are uncommon. They may include:

  • Allergic reactions
  • Muscle pain
  • Joint pain
  • Swollen lymph nodes
  • Nausea

It’s useful to mention adverse reactions are more common after the second dose rather than the first.

Who should and shouldn’t get vaccinated with this vaccine?

The Pfizer-BioNTech vaccine is suitable for persons aged 16 and older. Most adults are eligible for this vaccine. However, you shouldn’t get this vaccine if any of these apply to you:

  • History of an allergic reaction to any ingredient in mRNA vaccine
  • Suffering from an allergic reaction after the first dose of this vaccine

The vaccine is meant to work for persons with underlying, chronic conditions. But, if you have concerns, you may benefit from consulting your doctor.


Moderna’s mRNA-1273 vaccine works just like Pfizer and BioNTech vaccine. Basically, it’s an mRNA-based vaccine that does not contain the live virus but aims to produce antibodies by inducing the immune system’s reaction to a specific protein (S protein)

The vaccine is administered in two doses, 28 days apart. Each vaccine vial contains 10 doses of 0.5 milliliters.

When was the vaccine issued?

The FDA approved Moderna’s vaccine on December 18, 2020. Canada authorized this vaccine on December 23, 2020, and European Union on January 6, 2021.

How many people have received the vaccine?

At least 62,88 million doses of the Moderna vaccine have been administered to Americans. These numbers change every day as the immunization process keeps moving forward.

How effective is the vaccine?

The vaccine has been shown to have an effectiveness of 92% in protecting against COVID-19, starting two weeks after the first dose. A study from the New England Journal of Medicine showed Moderna vaccine had the effectiveness of 94.1% at preventing COVID-19 illness.

Does the vaccine have side effects?

Common side effects in the injection site may include pain, redness, and swelling. Adverse reactions throughout the body include:

  • Chills
  • Fever
  • Headache
  • Muscle pain
  • Nausea
  • Tiredness

Most side effects are mild to moderate. The risk of severe side effects is low, and they may include allergic reactions.

Who should and shouldn’t get vaccinated with this vaccine?

Moderna’s vaccine is suitable for persons aged 18 years and older. Almost everyone should get this vaccine. The vaccine shouldn’t be administered to persons who had a severe allergic reaction to the first dose of the vaccine and men and women who are allergic to the ingredients of this vaccine. Pregnant and breastfeeding women may want to consult their healthcare provider first.

Johnson & Johnson

Johnson & Johnson’s JNJ-78436735 vaccine is different than Moderna and Pfizer’s. This is a viral vector vaccine. Essentially, the viral vector (or adenovirus) vaccine contains genetic material from the COVID-19 virus. The genetic material was inserted into a different kind of live virus, known as adenovirus. Here, a viral vector or adenovirus acts as a delivery system. Upon entering the cells, the viral vector delivers the COVID-19 virus’s genetic material. When that happens, the virus gives instructions to those cells to produce S protein. Just like with mRNA vaccines, fragments of S proteins appear on the surface of the cells, thus activating the production of antibodies. The vaccine can’t infect you, and genetic material doesn’t reach your DNA.

Janssen is a single-dose vaccine. One vial of this vaccine contains five doses of 0.5ml.

When was the vaccine issued?

On February 27, 2021, FDA issued emergency use authorization for the Janssen vaccine. Approval in Canada for this vaccine was received on March 5, 2021, and European Union authorized it on March 11, 2021.

How many people have received the vaccine?

About 2.73 million doses of the Johnson & Johnson vaccine have been administered so far in the United States.

How effective is the vaccine?

The Johnson & Johnson vaccine showed an effectiveness of 85% in preventing severe COVID-19 that doesn’t require hospitalization. The effectiveness in the U.S. was 72%, and overall efficacy across all studied geographical areas in their trial was 66%.

Does the vaccine have side effects?

Common side effects of the Janssen vaccine are the same as those of Pfizer and Moderna. While severe adverse reactions are unlikely, some people may experience an allergic reaction. The allergic reaction occurs within a few minutes up to an hour after vaccination. Your healthcare provider may ask you to stay at a vaccination place for monitoring.

Who should and shouldn’t get vaccinated with this vaccine?

Johnson & Johnson vaccine is meant for persons who are at least 18 years old. Generally speaking, the vaccine is suitable for most people. Those who shouldn’t get the vaccine are persons who are allergic to any of the ingredients contained in the formula.


AstraZeneca and Oxford’s AZD1222 vaccine belongs to the viral vector category, just like Johnson & Johnson’s vaccine. As mentioned above, these vaccines contain genetic material from the COVID-19 virus and a delivery system in the form of adenovirus or a viral vector.

Unlike Johnson & Johnson, the AstraZeneca vaccine is not a single-dose vaccine. Two shots are necessary for intervals of eight to 12 weeks. Each vial contains eight to 10 doses of 0.5ml.

When was the vaccine issued?

AstraZeneca was first approved in the U.K. on December 30, 2020. The approval of this vaccine in the E.U. arrived on January 29, 2021, and Canada authorized it on February 26. At the moment of writing this article, the AstraZeneca vaccine wasn’t approved in the U.S. The approval is expected to happen in the coming days or weeks.

How many people have received the vaccine?

AstraZeneca vaccine is not distributed in the U.S. just yet.

How effective is the vaccine?

The interim trial among adults in the United States, Chile, and Peru showed an effectiveness of 79%. 

Does the vaccine have side effects?

The side effects of the AstraZeneca vaccine are similar to what you might experience with other vaccines. In most cases, the adverse reactions range from mild to moderate. They generally include pain at the injection site, body chills, tiredness, and fever.

Who should and shouldn’t get vaccinated with this vaccine?

People aged 18 years or older can get the AstraZeneca vaccine. You shouldn’t get the vaccine if you had an allergic reaction to a previous dose or you are allergic to any component of this vaccine.

Where to learn about vaccines?

Sources of reliable information about vaccines include: –

CDC – –


The main focus of this post was on vaccines against COVID-19. These vaccines belong to mRNA and viral vector categories and have a high effectiveness rate. Consult your doctor if you are pregnant, breastfeeding, or if you are concerned about your medical condition.


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COVID-19 Vaccines: Who Is Eligible, How to Get Vaccinated, What to Expect?

Covid Vaccine

One of the best ways to tackle the ongoing COVID-19 pandemic is through immunization programs. At this point, several COVID-19 vaccines are available such as Pfizer-BioNTech, Moderna, and Johnson & Johnson / Janssen. The ongoing vaccination process may seem confusing, especially because most of us have never experienced this apocalyptic scenario before. To help you get informed, we are going to simplify the whole process in this post. Read on to see who is eligible for vaccination, how to apply, and other useful things you need to know.

Who is eligible for the COVID-19 vaccine?

COVID19 Vaccine

Pfizer-BioNTech vaccine has been authorized for ages 16 and up, while Moderna and Johnson & Johnson vaccines are approved for persons with ages 18 and up. At this point, over 150 million people (more than half the population) are eligible to receive a vaccine against COVID-19.

According to the CDC, the U.S. supply of vaccines is expected to be limited at first. For that reason, 

they issued recommendations to federal, state, and local governments regarding the priorities for vaccinations. The vaccine rollout is recommended to develop in three phases:

  • Phase 1a: healthcare personnel and residents of long-term care facilities to receive first doses of COVID-19 vaccines
  • Phase 1b: frontline essential workers (police officers, firefighters, corrections officers, USPS workers, food and agricultural workers, manufacturing workers, grocery store workers, public transit workers, teachers, daycare workers). People aged 75 years and older are also included in phase 1b of vaccine rollout.
  • Phase 1c: people aged 65-74 years (except for residents of long-term care facilities who received the vaccine in phase 1a), people aged 16-64 with an underlying medical condition, and other essential workers such as persons working in logistics and transportation, food service, information technology, and communications, media, public safety, law, and public health

It’s useful to keep in mind recommendations from the CDC are not binding. Each state has the right to determine priorities regarding vaccination. To check whether you’re eligible, you should visit the official public health website of your state for more specific vaccination eligibility requirements. In the “Useful COVID-19 vaccination resources” section, you can find the link with all state and territorial Health Department websites.

How to apply for the vaccine?

Covid Vaccine

The application process for the vaccine depends on each state. For that reason, it’s useful to visit the link with health department websites, find your state, and see how to apply. The link is available further in the article.

Some state and local health departments have set up platforms where people can confirm the eligibility, schedule an appointment, and confirm the vaccine they will take. However, some health departments have arranged mass vaccinations relying on a first-come, first-served approach.

Can I choose which vaccine against COVID-19 I get?

Since several vaccines against COVID-19 are available, it’s impossible not to wonder if and how you can choose which one to get. However, it’s highly unlikely any of us have any say in the matter. You probably won’t be able to choose the vaccine. Why? Well, numerous factors are involved, including limited supplies, the vaccines used by the health department in your area, and the time of vaccination. Again, it’s useful to check out the health department website of your state of residence. In the end, the type of vaccine doesn’t really matter, and people are advised to get any vaccine their health departments offer since they have high effectiveness.

Basically, at this point, you can’t choose the vaccine. But, you may be able to do so once they become commercially available. At the moment, you can’t buy a vaccine against COVID-19 in pharmacies. But, CVS, Walgreens, and other chain pharmacies may start offering vaccines in partnership with the federal government.

What does “fully vaccinated” mean?

A person is considered “fully vaccinated” two weeks after receiving the second dose of vaccines such as Pfizer-BioNTech and Moderna and two weeks after receiving a single-dose vaccine such as Johnson & Johnson / Janssen.

A common misconception is that a person is “fully vaccinated” as soon as they receive a vaccine, but that’s simply not true. You are not fully vaccinated immediately or if it has been less than two weeks since receiving a single-dose vaccine or the second dose of Pfizer and Moderna.

How to protect yourself and others when you’re fully vaccinated?

Disregarding all the rules and recommendations once you’re fully vaccinated is a huge mistake. Keep in mind we are still learning how the vaccines work. Once you are fully vaccinated, you can finally gather indoors with other fully vaccinated people without having to wear a mask. You can also gather indoors with people from 

other households without wearing a mask unless any of these men and women are in a high-risk group of developing severe symptoms of COVID-19.

In case you, as a fully vaccinated person, have been in contact with someone who has COVID-19, you don’t have to get tested unless you’re experiencing symptoms as well.

While all these are important changes, as a fully vaccinated person, you still need to be cautious in order to protect yourself and other people; you should still:

  • Wear a mask in public
  • Maintain social distancing (at least six feet apart)
  • Avoid crowds
  • Avoid poorly ventilated spaces
  • Delay your domestic and international travels

Always keep in mind that many people are still not vaccinated. So you need to be particularly careful in order to protect them. Also, make sure to watch out for symptoms of COVID-19.

Useful COVID-19 vaccination resources

State & Territorial Health Department Websites, CDC

COVID-19 Vaccine, CDC

COVID-19 Vaccines, U.S. Department of Health and Human Resources


Most people are eligible for COVID-19 vaccines, but each state determines their ultimate eligibility and priority requirements. Make sure to check the official website of the public health department of your state to learn more about the process. Remember, getting a vaccine doesn’t mean you are fully vaccinated immediately, and you should still be cautious to protect yourself and others.