*Dr. Kenneth Zweig contributed to Abigail Fagan’s pscychologytoday.com article, published on August 9, 2024
Understanding how your immune system responds to build protection.
Key points
- Vaccines trigger an immune response, causing mild symptoms similar to those of the actual infection.
- Side effects indicate your body is building immunity, which is a positive and expected reaction.
- Severe vaccine reactions are rare, making the benefits of vaccination far outweigh the risks.
The CDC recently recommended that all Americans six months and older receive one of the new COVID-19 vaccines available this fall. This guidance comes as COVID-19 infections increase in 39 states and territories. Given this update, revisiting the topic of vaccine side effects is timely.
Understanding Side Effects
To understand why vaccines cause side effects, it’s essential to grasp a bit of immunology. When someone gets sick from an infection, it’s not the infection that causes the illness but the body’s reaction to it. When the immune system detects an infection, it releases compounds like interferon, interleukin, and tumor necrosis factor (TNF).
These compounds activate the immune system to fight the infection but can also make a person feel sick. They cause the body to develop a fever, which can kill bacteria and viruses. Additionally, these chemicals can cause fatigue, achiness, and nausea, prompting the body to conserve energy to fight the infection rather than use it for other activities.
The Role of Vaccines
Vaccines are designed to simulate an infection, which can also trigger the release of these immune compounds. Essentially, immunizations are practice for the immune system. They prepare the body for a specific bacterial or viral infection by presenting an “antigen,” a part of the infectious agent that activates the immune system without causing the disease. Once the body encounters an antigen, it produces antibodies that “remember” the contagious agent, readying the immune system for future encounters.
Because vaccines use the same antigens found in bacteria and viruses, it’s common to experience symptoms after vaccination that are similar to those one might experience with the actual infection. For example, the tetanus vaccine can cause muscle pain, and the influenza vaccine can cause fever and fatigue. The COVID-19 vaccine can cause headache, fatigue, fever, and joint aches—symptoms also associated with COVID-19. This can lead to the misconception that vaccines can cause the illnesses they aim to prevent.
Why Side Effects Can Be Positive
A vaccine should trigger an immune reaction, so feeling ill after vaccination is a positive sign. It indicates that the body is building immunity. Experiencing mild symptoms means the immune system responds as expected, reducing the likelihood of severe illness later. Those who do not experience symptoms after a vaccine will still likely develop immunity without noticeable side effects.
Severe side effects from vaccines are infrequent. For instance, the rate of anaphylaxis due to the COVID-19 vaccine is about one in 100,000, significantly lower than the risk of severe illness from COVID-19 itself. Additionally, conditions like Guillain-Barre syndrome occur in approximately one in a million cases. The likelihood of such severe reactions is much lower than other everyday risks, including being struck by lightning.
It’s important to remember that immunity takes time to develop after completing a vaccine series. Therefore, it’s crucial to continue taking precautions to prevent infection. If severe symptoms such as shortness of breath or high fever occur, or if symptoms persist beyond two to three days after a vaccination, it’s advisable to contact a physician.
Benefits Outweigh the Risks
The benefits of vaccination far outweigh the risks, possibly more than any other preventive measure or treatment available. Vaccinations have nearly eradicated diseases like polio, smallpox, and measles. They also help prevent certain cancers, such as cervical and liver cancer and can reduce the risk of heart attacks and pneumonia, as seen with the flu vaccine.
Vaccinations, including COVID-19 vaccines, remain crucial in protecting individual and public health. Mild side effects can be managed with over-the-counter medications like Tylenol, and they indicate that the vaccine is working. A little discomfort now can prevent significant health issues later.