ABCs of Childhood Vaccine Safety

My blog, “Radio Listeners ‘Angry as Hornets’ About Dr. Walt’s Comments on Childhood Vaccination”  raised howls of protest from blog constituents. Many of those who wrote comments simply do not understand how safe and effective vaccines are. They don’t seem to understand how vaccines are tested and then how throughly they are followed once licensed. If you’re interested in the truth about vaccine safety, and not the spin, read on. With this information you’ll not only share my (and virtually the entire medical world’s) about the safety of vaccines, but you’ll be able to help others who have been, unfortunately, indoctrinated (and, in some cases, brainwashed) by the fringe and fanatical antivaccine crazies.

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First of all, there are some terms to remember:

  1. Pre-Clinical Studies: First tests of a vaccine, conducted on animals, 
  2. Clinical trials: Initial human studies done in 3 phases to test safety, doses, and effectiveness of a vaccine, 
  3. Adverse Reactions: Negative ways people react to vaccines, 
  4. Biologics License Approval: FDA approval of the vaccine and of the manufacturing plant where the vaccine is made, 
  5. Vaccine Lot: Each separate manufacturing run of a vaccine, and 
  6. VAERS: Vaccine Adverse Event Reporting System, a federal program that compiles reports from up to 200,000 healthcare providers and members of the public annually.

Creating Vaccines: Safety And Effectiveness Go Hand In Hand.

It takes a long time to develop a single vaccine —usually 10 years or more. Why? Because vaccines must be proven safe and effective before ever reaching the public.

Vaccines Start With Research … Research … and more Research. 

  • In the laboratory, scientists look for clues about how a bacterium or virus causes a disease, because making a vaccine starts with finding the cause.
  • Every human being has a genetic code—the thing that makes us unique—and so do viruses and bacteria.
  • When scientists learn the code for a disease, they can identify the points where a vaccine could make antibodies to fight off viruses or bacteria.
  • Computer models and lab tests help predict how the vaccine will affect the human immune system.

After Research, Testing Starts (But Not On People).

  • Once a prototype vaccine is created, the first studies are conducted in animals (these are called “pre-clinical studies”).
  • Animals are used because their immune systems are similar to those of humans. Tests on animals help predict the effect on people. 
  • These tests help to make sure a vaccine has no major side effects. If it does, it’s time to start over! 

Four Phases Of Clinical Trials On People: 

Phase I Involves Animal Testing. 

  • By now, years may have passed since scientists first started research. But the work is just beginning.
  • A vaccine that’s been proven safe on animals goes through four phases of trials on people. 
  • In Phase I, anywhere from 20 to 100 volunteers receive the vaccine.
  • The first phase is limited to just a few people, because scientists are triple-checking for safety, looking for serious side effects.

Phase II Trials Are Long And Complicated.

  • Hundreds of volunteers take part in Phase II trials.
  • These trials might take a few months, or they might last for years.
  • Safety, safety, safety—that’s still being studied in Phase II.
  • Phase II tests also explore how the human immune system responds to the vaccine.
  • Phase II Also Finds The Precise Dose.
  • Now the vaccine is fine-tuned. Phase II trials set:
    • (1) the most effective use of the vaccine, 
    • (2) the best dose for effectiveness and safety, and 
    • (3) the right number of doses.
  • Adverse reactions are recorded. Local reactions include redness and swelling where the vaccine is given. General bodily reactions, such as fever or muscle aches, are also tracked. 
  • Some Phase II volunteers do not get the vaccine being tested. Instead, they get either an already-licensed vaccine or another harmless substance (placebo).
  • Placebos and controlled testing enable researchers to compare reactions in an immunized person with reactions in someone who isn’t immunized with the vaccine under study. 

Now It’s On To Phase III, (And That’s The Longest One Of All).

  • Phase III trials may last several years. A few hundred to tens of thousands volunteers may be involved. 
  • Some volunteers receive another already-licensed vaccine instead of the vaccine under study. 
  • That way, researchers can compare one vaccine to another for adverse effects—anything from a sore arm to a serious reaction.
  • If everything about the proposed vaccine checks out for safety and effectiveness in Phase III, the manufacturer applies for a license from the Food and Drug Administration (FDA).

One License Won’t Do—There Have To Be Two

  • During the application phase, the FDA reviews everything: clinical trial results, product labeling, the manufacturing plant itself, and the manufacturing protocols.
  • A biologic license is the license the FDA gives for  the vaccine itself and for the manufacturing plant where the vaccine is made. 

Phase IV  Tracks Vaccines After Licensing.

  • A license can be recommended or refused. This decision is made after an FDA team of specialists (microbiologists, chemists, biostatisticians, and medical officers) assess the safety data from the vaccine trials. 
  • If a license is issued, post-licensure monitoring takes place.
  • Monitoring is the continual tracking of tens of thousands of people who have been immunized with the vaccine under study. 
  • Post-licensure monitoring gives valuable information about the vaccine’s long-term safety and effectiveness.

Every Lot Of Vaccine is Tested and Sampled

  • After a vaccine is approved and in production, samples of each lot (separate manufacturing run) of a vaccine must be submitted to the FDA before it can be released for use. 
  • Each lot must be tested for safety, potency, and purity to assure uniformity in every dose of vaccine given.
  • Why test each lot? Because vaccines are very sensitive. Changes in temperature during the manufacturing process, for example, can make them lose strength.

Vaccine Safety Datalink (VSD)

  • In 1990, the CDC started its Vaccine Safety Datalink project—VSD for short.
  • Eight large health maintenance organizations (HMOs) joined with the CDC to help keep an eye on vaccine safety.
  • Since its beginning in 1990, VSD has collected safety statistics on more than 7 million people who have received vaccines. These statistics are a powerful tool for assuring safety.

Vaccine Adverse Event Reporting System (VAERS)

  • Sometimes, rare side effects and delayed reactions don’t show up in clinical trials.
  • So, once a vaccine is released to the public, data on effects and reactions are gathered continually.
  • To make the gathering of information about potential side effects as complete as possible, the CDC and the FDA started a national system called the Vaccine Adverse Event Reporting System (VAERS) in 1990. 
  • Anyone can report to VAERS. More than 200,000 healthcare providers get reporting forms from VAERS to remind them to note reactions and enter them into the system.
  • You can get information about VAERS and submit VAERS reports here

Clinical Immunization Safety Assessment Centers (CISA)

  • In 2001 the Clinical Immunization Safety Assessment Centers (CISA) were started.
  • These Centers serve as an expert resource on vaccine adverse events for parents, patients, and healthcare providers. 
  • Prior to the CISA network there were no coordinated facilities in the United States that investigated, evaluated, and managed vaccine adverse events for individual patients. 
  • CISA Centers work together with CDC to systematically assess individual cases that have been reported to the Vaccine Adverse Reporting System (VAERS).

Vaccine Additives

  • Tiny amounts of three types of substances may be added to vaccines.
  • All Additives Are Disclosed.
    • Preservatives keep bacteria or fungus from growing, which could otherwise give vaccine recipients serious infections. 
    • Stabilizers help the vaccine keep its correct chemical composition even if conditions (such as temperature) change dramatically. 
    • Adjuvants boost the vaccine’s ability to provide an immune response.
  • Every vaccine comes with a package insert listing every ingredient, including every additive.
  • The insert lists every known adverse reaction ever reported, no matter how minor.
  • If you wonder just what’s in a vaccine, or are worried about allergic reactions, ask your doctor for a copy of the insert.
  • And if you have any other questions or concerns, talk with your doctor. 

Key Facts

  • As we’ve seen, vaccines are created slowly and carefully. Research, lab tests, and tests on human volunteers take years for each vaccine.
  • At every step, safety and effectiveness are checked, double-checked and triple-checked.
  • Even after a vaccine is licensed, the FDA and the CDC keep gathering information on adverse events and overall vaccine safety.

Additional Resources

  • Centers for Disease Control and Prevention website: Click “Vaccines & Immunizations,” then click “NIP Home Page” in the right column or go directly to the site here
  • National Immunization Hotline: 1-800-232-2522.
  • Parent’s Guide to Childhood Immunization: Publication available online here
  • For information on vaccine testing and licensing go to the FDA website here
  • For information about local health care resources go here: or look under “public health” in the blue pages of your local phone book
  • For information on children’s health insurance go here
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