Original source overview
What are vaccines?Vaccines are injections (shots), liquids, pills, or nasal sprays that you take to teach the immune system to recognize and defend against harmful germs. The germs could be viruses or bacteria.
Some types of vaccines contain germs that cause disease. But the germs have been killed or weakened enough that they won't make your child sick. Some vaccines only contain a part of a germ. Other types of vaccines include instructions for your cells to make a protein of the germ.
These different vaccine types all spark an immune response, which helps the body fight off the germs. Your child's immune system will also remember the germ and attack it if that germ ever invades again. This protection against a certain disease is called immunity.
Why do I need to vaccinate my child?Babies are born with immune systems that can fight most germs, but there are some serious diseases they can't handle. That's why they need vaccines to strengthen their immune system.
These diseases once killed or harmed many infants, children, and adults. But now with vaccines, your child can get immunity from these diseases without having to get sick. And for a few vaccines, getting vaccinated can actually give you a better immune response than getting the disease would.
Vaccinating your child also protects others. Normally, germs can travel quickly through a community and make a lot of people sick. If enough people get sick, it can lead to an outbreak. But when enough people are vaccinated against a certain disease, it's harder for that disease to spread to others. The entire community is less likely to get the disease. This is called "community immunity."
Community immunity is especially important for the people who can't get certain vaccines. For example, they may not be able to get a vaccine because they have weakened immune systems. Others may be allergic to certain vaccine ingredients. And newborn babies are too young to get some vaccines. Community immunity can help to protect them all.
Are vaccines safe for children?Vaccines are safe. They must go through extensive safety testing and evaluation before they are approved in the United States.
Some people worry that childhood vaccines could cause autism spectrum disorder (ASD). But many scientific studies have looked at this and have found no link between vaccines and autism.
Can vaccines overload my child's immune system?No, vaccines do not overload the immune system. Every day, a healthy child's immune system successfully fights off thousands of germs. When your child gets vaccines, they are getting weakened or dead germs. So even if they get several vaccines in one day, they are being exposed to a tiny amount of germs compared to what they encounter every day in their environment.
When do I need to vaccinate my child?Your child will get vaccines during well-child visits. They will be given according to the vaccine schedule. This schedule lists which vaccines are recommended for children. It includes who should get the vaccines, how many doses they need, and at what age they should get them. In the United States, the Centers for Disease Control and Prevention (CDC) publishes the vaccine schedule.
Following the vaccine schedule allows your child to get protection from the diseases at exactly the right time. It gives their body the chance to build up immunity before being exposed to these very serious diseases.
Encyclopedic background — Wikipedia
The following selected excerpts provide background on “Vaccination”. This related background source does not cover every aspect of the specific topic “Childhood Vaccines”; population-specific details and decisions should be checked in the original topic source. They are not a substitute for the source overview or current local clinical guidance. Each excerpt below comes from the fixed Wikipedia revision [W1].
Definition and overview [W1]
Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating the body's adaptive immunity, they help prevent sickness from an infectious disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results. Herd immunity protects those who may be immunocompromised and cannot get a vaccine because even a weakened version would harm them.
The effectiveness of vaccination has been widely studied and verified. Vaccination is the most effective method of preventing infectious diseases; widespread immunity due to vaccination is largely responsible for the worldwide eradication of smallpox and the elimination of diseases such as polio and tetanus from much of the world. According to the World Health Organization (WHO), vaccination prevents 3.5–5 million deaths per year. A WHO-funded study by The Lancet estimates that, during the 50-year period starting in 1974, vaccination prevented 154 million deaths, including 146 million among children under age 5. However, some diseases have seen rising cases due to relatively low vaccination rates attributable partly to vaccine hesitancy.
The first disease people tried to prevent by inoculation was most likely smallpox, with the first recorded use of variolation occurring in the 16th century in China. It was also the first disease for which a vaccine was produced. Although at least six people had used the same principles years earlier, the smallpox vaccine was invented in 1796 by English physician Edward Jenner. He was the first to publish evidence that it was effective and to provide advice on its production. The process was called vaccination because it was derived from a virus affecting cows (Latin: vacca, 'cow'). Louis Pasteur furthered the concept through his work in microbiology. Smallpox was a contagious and deadly disease, causing the deaths of 20–60% of infected adults and over 80% of infected children. When smallpox was finally eradicated in 1979, it had already killed an estimated 300–500 million people in the 20th century alone.
Mechanism of function [W1]
Vaccines are a way of artificially activating the immune system to protect against infectious disease. The activation occurs through priming the immune system with an immunogen. Stimulating immune responses with an infectious agent is known as immunization. Vaccination includes various ways of administering immunogens.
Most vaccines are given by injection as they are not absorbed reliably through the intestines. Live attenuated polio, rotavirus, some typhoid, and some cholera vaccines are given orally to produce immunity in the bowel. While vaccination provides a lasting effect, it usually takes several weeks to develop. This differs from passive immunity (the transfer of antibodies, such as in breastfeeding), which has immediate effect.
Reading this topic in context
Use “Childhood Vaccines” as a starting point for a focused discussion, rather than treating every statement in the broader encyclopedia article as applying to you. The original source overview and the background excerpts answer different questions: the overview explains the health topic for readers, while the encyclopedia supplies terminology and general context. Keep a record of which questions concern symptoms, a confirmed diagnosis, prevention, or an existing treatment. This helps a healthcare professional address the relevant issue without relying on an internet label.
Questions to take to a professional
1. Which vaccines are due under the child's local schedule?
2. How should we document earlier doses and discuss previous reactions?
Evidence, scope and next steps
The health-topic overview is attributed to MedlinePlus / the National Library of Medicine at the original topic link below. Wikipedia [W1] is a secondary background source; its references can support further reading, but their presence is not evidence that WellPrimer has independently reviewed every study. No clinical review, guideline certification or NLM endorsement is claimed. For screening intervals, diagnostic thresholds, pregnancy or child-specific advice and treatment choices, check current guidance in your country with a qualified professional. Do not start, stop or change a prescribed medicine based on encyclopedia excerpts. New or worsening symptoms need appropriate clinical assessment rather than more reading alone.
Attribution and reuse
[W1] Wikipedia contributors, “Vaccination”. Version 1380558930, edited 2026-10-16. Retrieved 2026-10-16. Fixed revision: https://en.wikipedia.org/w/index.php?title=Vaccination&oldid=1380558930. Contributor history: https://en.wikipedia.org/w/index.php?title=Vaccination&action=history. License: https://creativecommons.org/licenses/by-sa/4.0/ .
The MedlinePlus health-topic summary retains its original attribution. Wikipedia excerpts and the added compilation/commentary are shared under CC BY-SA 4.0; selections, section ordering and editorial reading prompts have been added. No images are reused. This is an educational compilation, not a clinician-reviewed guideline.