Vaccine Safety System: A Rigorous Process for Public Safety

When presented with a patient or parent with vaccine hesitancy—a phenomenon intensified by the COVID-19 pandemic—there are a few strategies healthcare providers can use to address patients’ concerns and strengthen confidence in vaccine services. One approach is to explain the rigorous and scientific process that vaccines go through before being approved, and recommended, by the Centers for Disease Control (CDC). 

Healthcare providers play an important role in educating patients and emphasizing the nation’s longstanding vaccine safety system, which CDC reports as the safest vaccine supply in U.S. history.

Journey to Approval

A new vaccine must pass through three phases of clinical trials approved by the Food and Drug Administration (FDA) before it earns a place in the CDC-approved vaccine rotation. The phases include the following:

  • Phase 1: Between 20 and 100 healthy individuals volunteer to receive the vaccine for researchers to measure the safety and efficacy of the vaccine, and check for potential side effects.

  • Phase 2: Testing is expanded to include several hundred volunteers to determine the most common side effects of the vaccine, which also allows researchers to monitor how volunteers’ immune systems respond.

  • Phase 3: Even more volunteers are enlisted for further testing of the vaccine. Control groups are used to compare differences in those who receive and do not receive the vaccine, and researchers conduct their final analysis. 

Once the vaccine completes these three phases, the FDA will determine if it is safe and effective, and whether the benefits of the vaccine outweigh the potential risks of the side effects. Only then will the FDA license the vaccine.

In a post-manufacturing phase, the FDA will test the vaccines again and inspect all manufacturing facilities. Despite this thorough process, the vaccine still has more hurdles to jump before reaching the doctor’s office.

Approval and Recommendation

The next step in the journey of a new vaccine is determining proper applications to the public. The Advisory Committee on Immunization Practices (ACIP) is a group of medical and public health experts responsible for determining appropriate ages to administer vaccines, number of doses required, recommended time between doses, and any precautions for administration. Among the experts invited to develop the vaccine schedules are stakeholders from the following organizations:

  • American Academy of Pediatrics (AAP)

  • American Academy of Family Physicians (AAFP)

  • American Colleges of Obstetricians and Gynecologists (ACOG)

  • And the American Academy of Physicians (ACP)

Finally, once a consensus is reached, the group submits their recommendations to the Director of the CDC for approval. After review and approval, the submission is published in the CDC’s Morbidity and Mortality Report (MMWR), making it an official CDC recommendation. Only then can a vaccine be considered for the schedule recommended to families.

Continuous Monitoring

Even after a new vaccine meets the standards of the FDA, the ACIP, the CDC and the US Department of Health and Human Services, these agencies and organizations continue to take precautions. For example, the FDA and CDC both closely monitor the vaccine after it is worked into the immunization rotation using a surveillance program called Vaccine Adverse Event Reporting System (VAERS). This program collects reports of adverse effects and potential side effects caused by the vaccine that parents and guardians, healthcare providers, manufacturers, and others can access anytime. And researchers continue to use these insights to improve the vaccines in use today.

Understanding Vaccine Recalls

In the rare event that a vaccine becomes contaminated, defective, or causes adverse reactions, it can be recalled or withdrawn. When a recall is issued, especially if safety is a concern, the FDA is committed to declaring the recall immediately. While recalls and withdrawals are uncommon, the vaccine recall process exists as a mechanism to prevent possible harm to patients. Recalls and withdrawals differ slightly depending on the vaccine defect:

  • Recalls occur when an FDA violation is subject to legal action and the vaccine is removed from the market by a manufacturer's own initiative, an FDA request, or an FDA order under statutory authority.

  • Withdrawals occur when a vaccine has a violation that is not subject to FDA legal action and the vaccine manufacturer removes the product on their own accord.

FDA violations span from irregularities found during quality control, such as low efficacy, to abnormal side effects, often identified by VAERS. After experiencing or witnessing any unexpected side effects, both patients and health professionals are urged to file a VAERS report. Tracking side effects and filing VAERS reports are critical parts of the recall process, as the data enables early detection of vaccine defects and strengthens the recall process, reducing the risk of patient harm.

A view into the process of bringing a new vaccine to the public highlights the level of care that researchers and public health agencies take to ensure new vaccines are as safe and effective as possible. It's as important to understand the rigorous vaccine approval process as it is to understand the infrequency of vaccine recalls and withdrawals. Knowing this, healthcare providers can confidently educate patients, ease any concerns, and continue to recommend vaccines as a safe, preventative health measure.   

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