Why Do Some People Have Reactions To Covid Vaccine

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Why Are Pfizer And Moderna Side Effects Worse After The Second Shot

Ask Allie: Why do some people get side effects from COVID vaccines?

The second dose of the Pfizer and Moderna vaccines is likely to cause more noticeable side effects. In both the Pfizer and Moderna vaccine clinical trials, more participants had symptoms like headache, fever, and body aches after the second dose. The effects tend to be more intense after the second shot because of the way your immune system responds to vaccines.

The Pfizer and Moderna COVID-19 vaccines are both reactogenic vaccines, which means they are likely to cause side effects. This doesnt mean, however, that everyone will have side effects, or that the vaccine doesnt work if it doesnt cause side effects. Heres a breakdown of how the vaccines produce an immune response and why the second dose typically results in stronger side effects.

If you have never been exposed to COVID-19 and get your first shot of the vaccine, the virus protein that the vaccine causes your cells to produce known as the spike protein is new to the body. This protein is harmless and will not infect you with the virus.

Your body recognizes the protein as an antigen, or something foreign, and starts reacting to it with inflammation at the injection site. This is why the first shot very commonly causes arm pain.

Even if you have had COVID-19, the Centers for Disease Control and Prevention still recommends getting fully vaccinated.

Throughout The Rest Of Your Body:

  • Tiredness
  • Fever
  • Nausea

Anyone who has had a severe allergic reaction after getting a mRNA COVID-19 vaccine , should not get another dose of either of the mRNA COVID-19 vaccines. Anyone who has had a severe allergic reaction after receiving Johnson & Johnsons Janssen COVID-19 vaccine, should not receive another dose of that vaccine.

Learn about getting a different type of COVID-19 vaccine after an allergic reaction.

And A Lack Of A Reaction To The Covid Vaccine Doesn’t Mean It Didn’t Work

In answering a Q& A with Cleveland.com, Amy Ray, MD, a director at MetroHealth, said people should not “use the presence or absence of side effects as ‘proof’ of immunity.” “If you don’t have side effects, it doesn’t mean your immune system isn’t working,” James Fernandez, MD, an allergy and immunology expert, told the news outlet. “I wouldn’t focus on those early side effects related to the vaccine to judge whether you had an response or not.”

Kelly Elterman, MD, a board-certified anesthesiologist in San Antonio, Texas, also explained in a recent article for GoodRx that a lack of side effects doesn’t correlate with decreased immunity. “Only about 50 percent of people vaccinated with either the Pfizer or Moderna vaccines experienced side effects other than arm pain, while 95 percent were protected from COVID-19 infection,” Elterman wrote. Additionally, less than half of Johnson & Johnson recipients developed side effects other than pain at the injection site, “while up to 74 percent were protected from COVID-19 infection.”

And if you’re curious as to how long your vaccine works for, Dr. Fauci Says Your COVID Vaccine Protects You For This Long.

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What Side Effects Have Been Reported After Covid

In its safety report, the Paul Ehrlich Institute, a German federal health agency that regulates and researches vaccines and biomedicines, lists known, yet very rare, side effects of the COVID-19 vaccines. They include, for example, myocarditis, an inflammation of the heart muscle, and pericarditis, an inflammation of the pericardium, whereby the causal relationship has not yet been conclusively clarified in the cases reported to date.

Nonetheless, the Standing Committee on Vaccination recommended on November 10 that people under 30 should no longer be vaccinated with the Moderna vaccine as pericarditis had been reported more frequently than with the BioNTech vaccine.

Why Do Some People Have Worse Side Effects Than Others

Why do some people experience side effects after the COVID

Based on peoples experiences, it appears that some have worse reactions to the shot than others. But scientifically there arent any confirmed reasons for this yet.

There arent really any distinguishing factors that would predispose one individual having more side effects versus the other, said Richard Dang, a pharmacist and assistant professor of clinical pharmacy at the University of Southern California. The only thing weve seen in the clinical data so far is that younger individuals seem to experience side effects at higher rates than older individuals, and we see that in the real world as well.

There have been reported cases in which those who previously had the virus endured harsher side effects after they received their vaccines.

Anecdotally, it does appear that people who may have had COVID-19 before their vaccine do tend to have those longer duration of symptoms, Kelley added. But were still gathering additional scientific data to really support this.

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What Are The Most Common Side

According to Public Health England, most side-effects from two Covid vaccines Pfizer/BioNTech and Oxford/AstraZeneca are mild and short-lived. These include soreness where the jab was given, feeling tired or achy and headaches. Uncommon side-effects include having swollen lymph nodes.

Early reports that some people had severe allergic reactions, particularly to the Pfizer jab, led the UKs Medicines and Healthcare products Regulatory Agency to offer new recommendations, including that anyone receiving the Pfizer jab be monitored for 15 minutes after the event.

Joint Statement From The International Coalition Of Medicines Regulatory Authorities And World Health Organization

Healthcare professionals and public health authorities have a central role in discussing vaccination against COVID-19 with their patients. Vaccines play a critical role in preventing deaths, and hospitalisation caused by infectious diseases, and are contributing to controlling the spread of the disease, thus their impact on infection and serious illness is significant. Both vaccinated and unvaccinated people also need to be aware of the additional protective behaviours required to control the pandemic locally.

The global impact of the COVID-19 pandemic has resulted in an unprecedented level of public interest in vaccines. This includes a focus on the development of vaccines and their regulatory review and safety monitoring. Much of this coverage has taken place through mass and social media. Reports of adverse events have led some people to express concerns about getting vaccinated, delay getting vaccinated or be strongly opposed to vaccination. There are also differences in individual confidence in national safety monitoring systems. Another challenge in communicating the importance of COVID-19 vaccination is that in many, but not all, children and young adults are less clinically affected by COVID-19 infection and therefore some may see limited value in vaccinating this population. Clear and consistent communication of evidence and uncertainties is therefore essential to support people in making the critical choice to be vaccinated.


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Why Do Reactions To Vaccines Differ And What Do They Tell Us

But not everyone experiences side effects after a COVID-19 vaccine. Some feel fine after both doses. Scientists dont really know why, says Sujan Shresta, an immunologist at the Center for Infectious Disease and Vaccine Research at the La Jolla Institute for Immunology, in California. But its not a surprise that each person mounts the immune response differently.

Several factors can contribute to this wide variation. Women, for example, typically have stronger immune reactions than men, which may be part of what makes them more prone to suffering from side effects from the shots.

We all have our own individualized immune system, says John Wherry, director of the institute for immunology at the University of Pennsylvania, in Philadelphia. Its almost like our own immune fingerprint thats driven by genetics, gender, diet, our environment, and even our life history, which are the things our immune system has been exposed to in the past and has been trained to respond to over the years.

Even if you dont have an unpleasant reaction, the vaccines are still doing their job, because the real work of the immune systemand of the vaccinestakes place during the second, or adaptive, phase of the immune response. During this phase, the spike protein generated via the vaccine trains the B-cells to produce antibodies that match the virus, and the T-cells to seek-and-destroy infected cells. But it takes days to weeks to provide this long-lasting protection against the virus.

What Can I Do To Mitigate Side Effects Before Taking The Vaccine

Understanding COVID-19 vaccine side effects, why second dose could feel worse

Poland recommends that individuals stay hydrated, eat properly and get enough sleep before their vaccine appointments. All of those things affect the health of our immune system.

You should avoid taking pain relievers before your shot because these medications may blunt the bodys immune response to the vaccine. You also shouldnt get a Covid-19 vaccine at the same time as another vaccine, like the flu or shingles vaccine, according to the CDC.

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Ask Derrick: Social Media & Vaccine Hesitancy

The commonly used term “long-term effects” cannot be separated from side effects in relation to vaccines. They are just side effects whose connection with the vaccine becomes apparent only after some time has passed. For example, if a side effect occurs in only one in a million people, the connection is only apparent when several million people have been inoculated.

The good thing about COVID-19 vaccines is that more than 7.2 billion doses have been administered worldwide so far, allowing rare side effects to be identified quickly.

“Because so many people have already been vaccinated and because many months have already passed since a lot of people received the vaccination, we can now be very certain about possible side effects,” immunologist Förster explained.

Range Of Side Effects

Because side effects can be a sign of a robust immune system training to detect and destroy the virus, younger people may be more likely to have stronger side effects than the elderly. And, in vaccines that require two shots, such as the Pfizer and Moderna vaccines, side effects may also be worse after the second shot than the first one, because the T-cells remember the previous encounter with the spike protein. Without hesitation, the body quickly unleashes a strong immune response to destroy it including lots of side-effect-inducing cytokines.

“Consistently, the second shot is showing more side effects but better immune response,” Desai told Live Science.

The first dose teaches the immune system to recognize the virus and start producing antibodies and T cells against it, and the second shot is what helps the vaccine reach the full 94% to 95% efficacy, Desai said.

So, why do people tend to report stronger side effects from the COVID-19 vaccines than from some other vaccines, such as those for the flu? The mRNA COVID-19 vaccines may trigger stronger side effects than the flu shot in part because these vaccines stimulate a stronger immune response, Desai said.

People who previously recovered from COVID-19 are also likelier to have strong side effects even after the first shot. That’s because their immune systems have already been primed to react to the virus, Bailey said.

Individual differences, such as stress level and diet, can also influence side effects, Desai said.

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Why Do The Common Side

The sore arm can be either due to the trauma of the needle in the muscle, or local inflammation in the muscle probably because of the chemicals in the injection, said Prof Robert Read, head of clinical and experimental sciences within medicine at the University of Southampton and director of the National Institute of Health Researchs Southampton Biomedical Research Centre.

The other common side-effects the muscle aches, flu-like illness and fatigue are probably due to generalised activation of the immune system caused by the vaccine. What this means is that the white blood cells that are stimulated by the vaccine to make antibodies themselves have to secrete chemicals called cytokines, interferons and chemokines, which function to send messages from cell to cell to become activated.

Read said that for some people the process was without symptoms, but for others it generated these common side-effects.

First A Recap On What Causes Covid

Why do some people get side effects after COVID

COVID-19 vaccine side effects are either a physical manifestation of your bodys immune response which is the case for most people or an allergic reaction, said Jesse Erasmus, acting assistant professor in the department of microbiology at the University of Washington School of Medicine.

Erasmus said the side effects you have from a shot typically depend on the type of vaccine technology thats used to create the immunization and how those components interact with your immune system.

In terms of the coronavirus shots, all the vaccines that are currently in emergency use authorization have very similar side effect profiles, said Colleen Kelley, an associate professor of infectious diseases at Emory University School of Medicine and principal investigator for Moderna and Novavax Phase 3 vaccine clinical trials at the Ponce de Leon Center clinical research site in Atlanta.

Kelley thinks the COVID-19 shot side effects mainly stem from the body responding to the spike protein the vaccine introduces to the immune system, which helps it recognize the spike protein on the coronavirus should it enter the body.

When it comes to allergic reactions to the vaccine, which are rare, a hypothesis for mRNA vaccines is that people may be allergic to a component called polyethylene glycol, a common food additive, Erasmus said.

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Helpful Tips To Relieve Side Effects

Talk to a doctor about taking over-the-counter medicine, such as ibuprofen, acetaminophen, aspirin , or antihistamines for any pain and discomfort experienced after getting vaccinated.

People can take these medications to relieve side effects after vaccination if they have no other medical reasons that prevent them from taking these medications normally. Ask your childs healthcare provider for advice on using a non-aspirin pain reliever and other steps you can take at home to comfort your child after vaccination.

It is not recommended to take these medicines before vaccination for the purpose of trying to prevent side effects.

Why Is The Second Dose Often Worse Than The First

Dr. Marcelin explains, “It’s really the immune system that is showing us that it works that it remembers that we got the first vaccine. The point of the vaccination is to give our bodies that information to store away. So in the future, when it encounters something that looks like this coronavirus again, it will be able to rev up really quickly.”

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Health & Wellnesssore After Getting The Covid

Dr. Anne Liu, an infectious disease physician at Stanford Health Care in Palo Alto, California, said that the “majority of people” in clinical trials for the Moderna and Pfizer-BioNTech vaccines had “local side effects,” which means they felt pain or swelling at the injection site.

“As far as more significant, systemic side effects, it was a minority of patients, especially for the first injection,” said Liu, referring to symptoms like fatigue, chills, muscle aches or fevers. “Most people are not going to have systemic side effects.”

In some rare cases, people have experienced anaphylactic reactions to the vaccine. Some have also experienced mild skin reactions, like delayed redness at the injection site.

Dr. David Dowdy, an epidemiologist and associate professor at the Johns Hopkins Bloomberg School of Public Health, said that “every other vaccine we’ve ever given” has similar effects: Some people may experience “much stronger side effects,” which others “don’t feel those side effects at all.”

How Many People Experience Pfizer And Moderna Side Effects

Explained: Why do some people get side effects after taking Covid-19 vaccines?

Most people may experience at least one side effect after getting their dose the most common being an injection site reaction . In the first few months after the Pfizer and Moderna vaccines were authorized, 70% to 75% of people reported this side effect after getting either dose.

Additionally, 50% of people reported systemic side effects after their first dose, which jumped to about 70% after the second dose.

Chills and fever, which were reported by only about 9% of people after their first dose, went up to about 30% after the second dose. Similarly, joint pain was more common after the second shot, going from about 9% to 26% .

During the Pfizer and Moderna clinical trials, side effects were reported more frequently in younger people getting the vaccine. Below well review a few other factors that might influence your likelihood of experiencing side effects.

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How Often Do Side

Dr. Lynora Saxinger, an infectious disease expert at the University of Alberta in Edmonton, said cases of adverse effects are increasing because so many people are now getting vaccinated. The percentage of those that develop these mild to moderate side-effects is still quite low compared with the number of people being immunized.

She said that while more severe effects are possible a small number have experienced serious allergic reactions those events are rare.

Fever was common after the first dose of Pfizer and “very common” defined as present in 10 per cent of participants or more after the second dose. It was uncommon after the first dose of Moderna but very common after the second.

Brown said effects are generally more apparent following second doses because the body has built up a stronger immune response from the initial jab.

While Saxinger said a fever is a “strong reaction” to a vaccine, it shouldn’t last more than a few days. She also said that taking anti-inflammatories before a vaccine to lessen possible effects isn’t advised, since you want to elicit that immune response.

“It looks like mRNA vaccines are particularly talented at mimicking infection,” she said. “That very targeted and strong immune response is what we ultimately want.”

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