Vaccine scientists work under the premise that it is always better to prevent a disease than to treat it. As a result, research is constantly being conducted to identify microorganisms, viruses or toxins that merit preventative action, and to develop corresponding vaccines.
Candidate vaccines are developed and rigorously tested throughout various stages of their development starting with laboratory tests which are followed by a three-stage clinical trial program. The Food and Drug Administration (FDA) ultimately evaluates vaccines and determines their date of release for medical use based on three main variables:
- Stability during shelf life
The Journey of Your Child's Vaccine
Before a new vaccine is ever given to people, extensive lab testing is done that can take several years. Once testing in people begins, it can take several more years before clinical studies are complete and the vaccine is licensed.
How a New Vaccine Is Developed, Approved and Manufactured
Food and Drug Administration (FDA) sets rules for the three phases of clinical trials to ensure the safety of the volunteers.
Researchers test vaccines with adults first. Between 20-100 healthy volunteers receive the test vaccine. Researchers study to determine:
- Is this vaccine safe?
- Does this vaccine seem to work?
- Are there any serious side effects?
- How is the size of the dose related to side effects?
Several hundred additional, healthy volunteers receive a test vaccine and researchers determine:
- What are the most common short-term side effects?
- How are the volunteers’ immune systems responding to the vaccine?
Hundreds or thousands of volunteers participate in the Phase 3 test, after which researchers determine:
- How do people who get the vaccine and people who do not get the vaccine compare?
- Is the vaccine safe?
- Is the vaccine effective?
- What are the most common side effects?
FDA licenses a vaccine only if:
- It’s safe and effective
- Benefits outweigh risks
Vaccines are made in batches called lots.
Manufacturers must test all lots to make sure they are safe, pure and potent. The lots can only be released once FDA reviews their safety and quality. The FDA inspects manufacturing facilities regularly to ensure safety and quality.
For more information, visit the FDA. If the FDA licenses a vaccine, experts may consider adding it to the recommended immunization schedule
How a Vaccines Is Added to the U.S. Recommended Immunization Schedule
The Advisory Committee on Immunization Practices (ACIP) is a group of medical and public health experts. Members of the American Academy of Pediatrics (AAP) and American Academy of Family Physicians (AAFP) are among some of the groups that also bring related immunization expertise to the committee. This group carefully reviews all available data about the vaccine from clinical trials and other studies to develop recommendations for vaccine use.
When making recommendations, ACIP considers:
- How safe is the vaccine when given at specific ages?
- How well does the vaccine work at specific ages?
- How serious is the disease this vaccine prevents?
- How many children would get the disease the vaccine prevents if we didn’t have the vaccine?
ACIP recommendations are not official until the CDC Director reviews and approves them and they are published. These recommendations then become part of the United States official childhood immunization schedule.
New vaccine to protect your child against a disease is added to the schedule.
For more information, visit the CDC. After being added to the U.S. Recommended Immunization Schedule, health experts continue to monitor the vaccine’s safety and effectiveness.
How a Vaccine’s Safety Continues to be Monitored
FDA and CDC closely monitor vaccine safety after the public begins using the vaccine.
The purpose of monitoring is to watch for adverse events (possible side effects).
Monitoring a vaccine after it is licensed helps ensure that possible risks associated with the vaccine are identified.
Vaccine Adverse Event Reporting System (VAERS) collects and analyzes reports of adverse events that happen after vaccination. Anyone can submit a report, including parents, patients and healthcare professionals.
The Vaccine Safety Datalink (VSD) is a network of healthcare organizations across the U.S.
Healthcare information is available through the Vaccine Safety Datalink for a population of over 9 million people.
Scientists use VSD to conduct studies to evaluate the safety of vaccines and determine if possible side effects are actually associated with vaccination.
Vaccine recommendations may change if safety monitoring shows that the vaccine risks outweigh the benefits (like if scientists detect a new serious side effect).
For more information, visit the CDC
The United States currently has the safest vaccine supply in its history. These vaccines keep children, families and communities protected from serious diseases.
See a graphic representation of a Vaccine's Journey