Emergency Preparedness and Vaccine Safety
CDC’s Immunization Safety Office (ISO) helps monitor vaccine safety, including during emergency responses and for many new vaccines.
Monitoring vaccine safety is important because:
- When new vaccines are released, scientists continue to analyze data about their safety outside of controlled clinical trials. Close monitoring of vaccines allows for early detection and assessment of potential safety concerns.
- If CDC detects unusual or unexpected patterns of adverse events following vaccination or other evidence of a potential safety concern, further assessment will be conducted to evaluate for a safety risk and public health action will be taken if necessary.
V-safe is a safety monitoring system that helps CDC monitor the safety of select new vaccines approved for use in the United States. The system uses text messaging, email, and web surveys to check in with vaccine recipients following vaccination. If anyone reports that they experienced a symptom or health event that needed medical attention, CDC will send them a text message or email with a link to complete a Vaccine Adverse Event Reporting System (VAERS) report to provide more information.
The Vaccine Adverse Event Reporting System (VAERS), co-managed by CDC and Food and Drug Administration (FDA), accepts reports of possible adverse events following vaccination. Anyone—patients, parents, healthcare professionals, vaccine manufacturers, and others—can submit a report to VAERS. CDC and FDA vaccine safety experts analyze reports and use statistical techniques to detect unusual or unexpected patterns that might indicate a safety problem with a vaccine.
The Vaccine Safety Datalink (VSD) project is a CDC collaboration with several integrated healthcare organizations. VSD uses electronic health record data to monitor vaccine safety and conduct vaccine safety studies based on questions or concerns raised from the medical literature and reports to the Vaccine Adverse Events Reporting System (VAERS). An analytic method called rapid cycle analysis (RCA) allows CDC to monitor vaccine safety in near real time so the public can be informed quickly of possible risks.
The Clinical Immunization Safety Assessment (CISA) Project is a CDC collaboration with a national network of vaccine safety experts. At the request of U.S. healthcare providers, CISA analyzes complicated health issues that might occur after vaccination and provides research on the risks associated with vaccines.
Vaccine Safety Coordinators positioned in 66 health departments in states, territories, large urban areas, and freely associated states carry out vaccine safety and emergency preparedness activities in coordination with CDC.
During the COVID-19 response, protocols, and standard operating procedures (SOPs) were developed to help CDC scientists and their public health partners conduct COVID-19 vaccine safety monitoring.
CDC has multiple systems for ongoing monitoring and evaluation of the safety of COVID-19 vaccines. SOPs and protocols to monitor outcomes related to the COVID-19 vaccines have been developed for each system.
Learn more about Ensuring the Safety of COVID-19 Vaccines in the United States
These SOPs are living documents and subject to updates as needed.
CDC is continuing to evaluate reports of people who developed myocarditis (inflammation of the heart muscle) after mRNA COVID-19 vaccination. Myocarditis after vaccination is rare and most of these people have recovered from their symptoms but more information is needed about the possible longer-term effects of myocarditis following vaccination. These evaluations are important to understand the risk-benefit balance of COVID-19 vaccination.
This national surveillance systems collects and reviews adverse events following vaccination. Included with routine data collection, VAERS team members will review all adverse events following COVID-19 vaccination and will collect information on specific outcomes. Gathered information will be reported out to FDA and CDC.
VAERS Standard Operating Procedures for COVID-19 Feb. 2022 Update [PDF – 37 pages] updated Feb. 2, 2022
The VSD is a collaboration between CDC and several integrated healthcare organizations across the United States that actively monitors the safety of vaccines and conducts studies about rare and serious adverse events following immunization. This system is also used to help determine whether possible adverse events identified in VAERS and other monitoring systems are related to vaccination.
Changes in Healthcare Use Following COVID-19 Infection [PDF – 20 pages] updated Dec. 7, 2022
VSD RCA Protocol Version 1.7 [PDF – 35 pages] updated Dec. 15, 2022
VSD Menstrual Irregularities Working Group (MI-WG) Protocol [PDF – 10 pages] updated Jan. 27, 2022
VSD Tree-Based Data Mining Protocol version 1.8 [PDF – 13 pages] updated Jan. 7, 2022
Development and Implementation of a Text- and Internet-Based monitoring System for Adverse Events Following COVID-19 Vaccination: A Pilot in Kaiser Permanente Southern California Protocol [PDF – 38 pages] updated April 13, 2021
VSD RCA Protocol Summary [PDF – 10 Pages] updated February 24, 2021
CISA helps healthcare providers in the United States with challenging health issues after vaccination through consultations with a team of vaccine safety experts. The experts analyze specific cases to understand adverse events and provide recommendations. CISA conducts research to identify and evaluate risks associated with vaccines, contributing to better vaccine safety practices.
CISA COVIDvax Work Plan [PDF – 29 pages] updated Dec. 5, 2020
The COVID-19 Vaccine Pregnancy Registry enrolled V-safe participants who reported they were pregnant at the time of vaccination or shortly thereafter.
COVID-19 Vaccine Pregnancy Registry Protocol Version 3 [PDF – 16 pages] updated October 27, 2022
Investigating Long Term Effects of Myocarditis
- Myocarditis Outcomes after mRNA COVID-19 Vaccination Investigation version 1 [PDF – 5 pages] updated Oct. 7, 2021
- Vaccine Adverse Event Reporting System (VAERS) Standard Operating Procedures for COVID-19 version 3 [PDF – 43 pages] updated Jan. 29, 2021
- Vaccine Adverse Event Reporting System (VAERS) Standard Operating Procedures for COVID-19 version 2 [PDF – 30 pages] updated Dec. 4. 2020
- Vaccine Adverse Event Reporting System (VAERS) Standard Operating Procedures for COVID-19 version 1 [PDF – 30 pages] updated Nov. 30, 2020
- VSD RCA Protocol version 1.3 [PDF – 33 pages] updated Nov. 12, 2021
- COVID-19 Vaccine Safety Evaluation in Pregnant Women and their Infants Protocol – version 1.5 [PDF – 37 pages] updated June 29, 2021
- COVID-19 Vaccine Safety Evaluation in Pregnant Women and their Infants Protocol – version 1.0 [PDF – 20 pages] updated June 17, 2021
- COVID-19 Vaccine safety, Spontaneous Abortion (SAB) and Stillbirth in the VSD Protocol version 1.5 [PDF – 28 Pages] updated Apr. 28, 2021
- COVID-19 Vaccine-Mediated Enhanced Disease (VMED) and Vaccine Effectiveness in the VSD Protocol version 1.2 [PDF – 18 pages] updated Apr. 27, 2021
- VSD Tree-Based Data Mining Protocol version 1.3 [PDF – 13 pages] updated Apr. 1, 2021
- VSD RCA Protocol version 1.1 [PDF – 31 Pages] updated March 3, 2021
- Long COVID-19: Changes in Healthcare Utilization Following Infection with SARS-CoV-2 Protocol [PDF – 11 pages] updated February 18, 2021
- V-safe protocol – version 6 [PDF – 87 pages] updated Oct. 21, 2022
- V-safe protocol – version 5 [PDF – 87 Pages] updated April 18, 2022
- V-safe Protocol – version 4 [PDF – 69 Pages] updated March 10, 2022
- V-safe Protocol – version 3 [PDF – 55 pages] updated May 20, 2021
- V-safe Protocol – version 2 [PDF – 58 pages] updated Jan. 28, 2021
- V-safe Protocol – version 1 [PDF – 56 pages] updated Nov. 19, 2020
- V-safe nested case-control study: Severe systemic adverse events following mRNA COVID-19 vaccination among those with prior history of SARS-CoV-2 infection [PDF – 27 Pages] updated May 27, 2021
COVID-19 Vaccine Pregnancy Registry
- COVID-19 Vaccine Pregnancy Registry Protocol Version 2 [PDF – 11 pages] updated March 18, 2021
- COVID-19 Vaccine Pregnancy Surveillance Version 1 [PDF – 11 pages] updated Dec. 28, 2020
In 2022, CDC responded to an mpox outbreak in the United States. CDC played a vital role in monitoring the safety of vaccines used to prevent mpox, utilizing surveillance systems like V-safe and VAERS to collect data on adverse events. This allowed CDC to promptly address any potential side effects or adverse reactions and share information with public health partners.
In response to concern about smallpox possibly being used as a biological weapon, President George W. Bush launched the National Smallpox Pre-Event Vaccination Program on December 13, 2002. Studying the vaccine’s safety was an essential aspect of the program. A system for passive surveillance (a scientific term which means that anyone can choose to report possible side effects) was built from VAERS.
For more information, read the special supplement of the journal Clinical Infectious Diseases, entitled “Posteradication Vaccination Against Smallpox.”
ISO played a major role in the H1N1 influenza pandemic of 2009 and 2010. CDC used VAERS and VSD to monitor the safety of the H1N1 influenza A vaccine. In addition, the Department of Health and Human Services established the H1N1 Vaccine Safety Risk Assessment Working Group to review 2009 H1N1 vaccine safety data as it accumulated.
For more information, read The 2009 H1N1 Pandemic: Summary Highlights, April 2009-April 2010.