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.

Vaccine Safety Tools

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.

Protocols and Standard Operating Procedures For COVID-19

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.

Investigating Long Term Effects of Myocarditis

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.

Myocarditis Outcomes after mRNA COVID-19 Vaccination Investigation version 2 [PDF – 5 pages] updated Feb. 20, 2022 

Vaccine Adverse Event Reporting Systems (VAERS)

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

Vaccine Safety Datalink (VSD)

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

COVID-19 Vaccine Mediated Enhanced Disease (VMED) and Vaccine Effectiveness in the VSD Protocol – version 1.9 [PDF – 19 pages] updated April 13, 2023

Mortality and Vaccination with COVID-19 Vaccines Study Protocol Version 1.3 [PDF – 13 Pages] updated June 6, 2022

VSD RCA Protocol Version 1.7 [PDF – 35 pages] updated Dec. 15, 2022

COVID-19 Vaccine Safety, Spontaneous abortion (SAB) and Stillbirth in the VSD Case Control Studies Protocol – version 1.0 [PDF – 34 pages] updated Feb. 7, 2022

COVID-19 vaccine safety, Spontaneous Abortion (SAB) and Stillbirth monthly surveillance in the VSD Protocol – version 2.0 [PDF – 29 pages] updated Feb. 4, 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

COVID-19 Vaccine Safety Evaluation in Pregnant Women and their Infants Protocol – version 1.7 [PDF – 42 pages] updated Dec. 20, 2021

Infections through 6 months of age among infants born to women to received COVID-19 vaccination while pregnant or breastfeeding protocol – version 1.2 [PDF – 18 pages] updated Dec. 14, 2021

Monitoring safety of SARS-CoV-2 vaccines in an expanded underserved population in the Vaccine Safety Datalink Protocol [PDF-16 Pages] updated Sept. 28, 2021

COVID-19 Vaccination Knowledge, Attitudes and Beliefs Survey Protocol Version 5.0 [PDF – 22 Pages] updated July 7, 2021

Simultaneous vaccine administration and co-administration with COVID-19 vaccine in the Vaccine Safety Datalink Protocol [PDF – 22 pages] updated May 2021

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

Clinical Immunization Safety Assessment (CISA) Project

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

COVID-19 Vaccine Pregnancy Registry

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

Examples of Past Vaccine Safety Emergency Responses