Side effects can be a natural part of the vaccination process. Fortunately, not everyone experiences them. It’s common knowledge the Pfizer/BioNTech and Moderna vaccines – especially the second dose – often cause headaches, fatigue and sometimes fever. Few people understand why VUMI® Canada wants you to be as informed as possible.
Simply stated, Dose #2 builds on Dose #1. When your body experiences the second injection, your immune system recognizes the threat, and takes it seriously. The side effects are evidence your immune system is working against the virus.
Understanding the Science: When the immune system detects a virus, it dispatches cells and molecules to memorize its features to fight it off more quickly in the future. The Pfizer and Moderna vaccines teach the body to fight via a genetic molecule called “mRNA,” found naturally in human cells. Once you receive the vaccine, the mRNA instructs your cells to produce a coronavirus protein called “spike,” a molecule that causes powerful, infection-fighting antibody responses in people battling COVID-19.
To ensure the passage of mRNA into cells, vaccine makers embedded the molecules in greasy bubbles called lipid nanoparticles. These fatty spheres do not resemble anything naturally present in the body. Therefore, they alert the sensors of fast-acting immune cells, or innate immune cells, to seek out foreign matter in the body. Once they spot the nanoparticles, these cells dispatch molecular alarms called “cytokines” to recruit other immune cells to the site of injection. This influx of cells and molecules makes the injection
site swollen and sore. The cells produce more cytokines, flooding the rest of the body with signals that can trigger system-wide symptoms such as fever and fatigue. The nature of mRNA might explain why Moderna’s shot, which contains three times as much of the genetic material as Pfizer’s, has been linked to more side effects in trials.
The attacking cells are not very long-lived. Their goal is to seek out and destroy anything that looks strange. Within a day or two of the injection, cytokine production slows down and side effects start to fade.
Concurrently, the innate immune cells pass on their job to a different part of the immune system, called adaptive immunity. These molecules and cells, (antibodies and T cells) stand ready to launch an attack on specific pathogens should they try to infect the body again.
T cells and B cells, the cells that make antibodies, need a few days to understand the spike’s features before they can respond. By the time you receive your second injection these adaptive cells have learned their lesson, and react quickly. Interestingly, some of these cells actually linger at the site of injection to fend off another possible attack. Stimulated anew, these sentinel cells blast out cytokines, layering on an extra wave of inflammation. In some people, these complex reactions cause fevers, aches and prolonged exhaustion.
Here’s the key takeaway: side effects signify that both branches of the immune system are engaging as they should—cementing the memory of the coronavirus’s spike protein in some of the body’s most powerful cells. But, fear not, a lack of side effects does not mean the vaccine isn’t working as it should. Everyone’s body is different.
The side effects to Pfizer and Moderna vaccines can lay you low for 24 hours, give or take. But, 24 hours of side effects surely beat a full-on case of COVID-19, and its debilitating, months-long symptoms that have killed more than 2 million people.
For more information about vaccines, please download our informative guide. Also, keep checking our website for more updates.
Source: “The Second COVID-19 Shot Is a Rude Reawakening for Immune Cells” by Katherine Wu in The Atlantic, February 2, 2021
