Emergency Preparedness and Vaccine Safety

Johnson & Johnson’s Janssen COVID-19 Vaccine: CDC and FDA have recommended that use of Johnson & Johnson’s Janssen (J&J/Janssen) COVID-19 Vaccine resume in the United States, effective April 23, 2021. However, women younger than 50 years old should be aware of the rare risk of blood clots with low platelets after vaccination, and that other COVID-19 vaccines are available where this risk has not been seen. If you received a J&J/Janssen vaccine, here is what you need to know. Read the CDC/FDA statement.

CDC’s Immunization Safety Office (ISO) prepares for emergencies by ensuring that robust systems are in place to rapidly monitor vaccine safety in the event of an emergency vaccination program.

During an emergency involving mass vaccination, monitoring vaccine safety is important because:

  • The vaccines being used might be new. With any new vaccine, initial safety data might be limited. In this situation it will be important to closely monitor safety to detect unexpected or concerning patterns.
  • Large numbers of vaccines might be given in a short period of time, and therefore more adverse events (possible side effects) might be reported to the Vaccine Adverse Event Reporting System (VAERS).
  • Public awareness of vaccination programs during an emergency might stimulate reporting to VAERS resulting in higher volume reporting than during non-emergency situations

Vaccine Safety Tools in an Emergency

  • V-safe is a new smartphone-based, after-vaccination health checker for people who receive COVID-19 vaccines. V-safe uses text messaging and web surveys from CDC to check in with vaccine recipients following COVID-19 vaccination. V-safe also provides second vaccine dose reminders if needed, and telephone follow up to anyone who reports medically significant (important) adverse events
  • VAERS accepts vaccine adverse event reports from patients, parents, healthcare professionals, vaccine manufacturers and others.  CDC and FDA scientists review reports and use statistical techniques to detect unusual or unexpected patterns that might indicate a vaccine safety problem.
  • The Clinical Immunization Safety Assessment (CISA) Project is a national network of vaccine safety experts which addresses vaccine safety issues, conducts clinical research and assesses complex clinical adverse events following vaccination.
  • The Vaccine Safety Datalink (VSD) project gathers information on vaccines given to members of certain health care organizations around the country. A system called rapid cycle analysis allows CDC to address vaccine-associated health problems very quickly.
  • Vaccine Safety Coordinators positioned in 62 health departments in states, territories, large urban areas and freely associated states carry out vaccine safety and emergency preparedness activities while coordinating with CDC.

Protocols and Standard Operating Procedures For COVID-19

In the COVID-19 response, protocols and standard operating procedures (SOPs) have been developed to help public health professionals perform tasks related to COVID-19 vaccine safety and monitoring. These SOPs also provide guidance to CDC staff when something may seem out of the ordinary or does not have a specific set of instructions. CDC has multiple vaccine safety monitoring systems in place to help keep COVID-19 vaccines safe. SOPs to monitor COVID-19 vaccines have been developed for each of the systems.

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.

V-safe After Vaccination Health Checker

V-safe is an active surveillance program to monitor the safety of COVID-19 vaccines during the period when the vaccines are authorized for use under Food and Drug Administration (FDA) Emergency Use Authorization (EUA) and possibly early after vaccine licensure. The purpose of v-safe surveillance is to rapidly characterize the safety profile of COVID-19 vaccines when given outside a clinical trial setting and to detect and evaluate clinically important adverse events and safety issues that might impact policy or regulatory decisions.


V-safe Protocol – version 2 pdf icon[PDF – 58 pages] updated Jan. 28, 2021

V-safe Pregnancy Surveillance (amendment) pdf icon[PDF – 11 pages] updated: Dec. 29, 2020

Vaccine Adverse Event Reporting Systems (VAERS)

VAERS is a national surveillance systems collects and reviews adverse events following vaccination. In addition to routine data collection activities, VAERS team members will review all adverse events following COVID-19 vaccination daily and will collect information on specific outcomes. Gathered information will be reported out to FDA and CDC.


VAERS Standard Operations Procedures pdf icon[PDF – 43 pages] updated Jan. 29, 2021

Vaccine Safety Datalink (VSD)

The VSD is a collaboration between CDC and nine integrated healthcare organizations across the United States that conducts active vaccine safety surveillance and research. This system is also used to help determine whether possible side effects identified using VAERS are actually related to vaccination.


VSD RCA Protocol Summary pdf icon[PDF – 10 Pages] updated February 24, 2021

VSD RCA Protocol version 1.1 pdf icon[PDF – 31 Pages] updated March 3, 2021

Clinical Immunization Safety Assessment (CISA) Project

The CISA Project uses clinical experts located across the country to monitor and address vaccine-related safety concerns, including advising on special cases for healthcare providers and health departments. The project’s clinical consultation has an extension on-call service to address COVID-19 vaccine safety related inquiries, called CISA COVIDvax.


CISA COVIDvax Work Plan pdf icon[PDF – 29 pages] updated Dec. 2, 2020

Examples of Past Vaccine Safety Emergency Responses