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Content on this page was developed during the 2009-2010 H1N1 pandemic and has not been updated.

  • The H1N1 virus that caused that pandemic is now a regular human flu virus and continues to circulate seasonally worldwide.
  • The English language content on this website is being archived for historic and reference purposes only.
  • For current, updated information on seasonal flu, including information about H1N1, see the CDC Seasonal Flu website.

Influenza A (H1N1) 2009 Monovalent Vaccine Safety Monitoring: CDC Planning Recommendations for State, Local, Tribal, and Territorial Health Officials

August 21, 2009, 1:00 PM ET

Vaccine Safety Monitoring

Vaccines to protect against the pandemic H1N1 2009 influenza virus are being developed. These influenza A (H1N1) 2009 monovalent vaccines (2009 H1N1 monovalent vaccines) and are anticipated to become available in the fall of 2009. The Advisory Committee on Immunization Practices (ACIP) has made recommendations regarding who should receive the 2009 H1N1 monovalent vaccine when it becomes available, including priorities for use of initial doses of vaccine. Coordination and communication for vaccine safety related activities at all levels are critical for a mass 2009 monovalent H1N1 vaccination campaign. Vaccine safety monitoring is a shared responsibility among the federal government, state and local health departments, vaccine manufacturers, healthcare providers, and other partners. This planning guidance addresses key components of the vaccine safety monitoring plan for 2009 H1N1 monovalent vaccines and presents suggested roles for state, local, tribal and territorial health officials involved in this monitoring. This guidance will be updated as more information about the 2009 H1N1 monovalent vaccination program becomes available.


The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) closely monitor the safety of influenza and other vaccines used in the United States. Licensed 2009 H1N1 monovalent vaccines will be produced using the same manufacturing process as seasonal influenza vaccines. All seasonal influenza vaccines licensed in the United States are produced in eggs and they do not contain adjuvants.1 When seasonal influenza vaccines are administered according to licensed indication and usage information they are safe; however vaccines, like any medical product, carry some risks. It is anticipated that the safety profile of licensed 2009 H1N1 monovalent vaccines will be similar to seasonal influenza vaccines; serious adverse events after vaccination are uncommon.2

Adverse events following immunization may be coincidental or causally related to the vaccine. The following are objectives of the 2009 H1N1 monovalent vaccine safety monitoring response:

  • Timely identification of clinically significant adverse events following receipt of 2009 HINI monovalent vaccine
  • Rapid evaluation of serious adverse events identified after 2009 H1N1 monovalent vaccine to determine the public health importance
  • Evaluation of the risk of Guillain-Barré syndrome (GBS) associated with the 2009 H1N1 monovalent vaccine3

Vaccine Adverse Event Reporting System (VAERS)

VAERS will be the front-line monitoring system for collecting and analyzing voluntary reports of adverse events following 2009 H1NI monovalent vaccination:

  • VAERS is a US vaccine safety surveillance system, co-managed by CDC and FDA.
  • VAERS is a key mechanism to identify potential vaccine safety concerns. Generally VAERS cannot determine if an adverse event was caused by vaccine but can help determine if further investigations are needed.
  • Healthcare providers are encouraged to report clinically significant adverse events after 2009 H1N1 monovalent vaccine or any vaccine to VAERS. A report should be submitted even if the reporter is not certain that the vaccine caused the event.
  • Anyone can submit a VAERS report, including healthcare providers, vaccine providers, public health officials, vaccine manufacturers, and persons vaccinated or their caregivers.
  • Reports may be filed securely online, by mail, or by fax. Report forms are available online or can be obtained by calling 1-800-822-7967 to request reporting forms or other assistance.
  • After a VAERS report is received, VAERS staff will collect additional information on reports of clinically serious adverse events4 by contacting the reporter and/or through other sources that may have relevant follow-up information. CDC and FDA staff will analyze the VAERS data to look for potential vaccine safety concerns.
  • Additional staff are being recruited to increase the capacity to process and follow-up on VAERS reports in a timely manner; state health officials will not have responsibility to follow-up on these VAERS reports.
  • VAERS data without identifiers may be accessed through the CDC Wide-ranging Online Data for Epidemiologic Research (WONDER) public database or for download at within about 6 weeks after CDC receives the VAERS report.

Other Vaccine Safety Monitoring Activities

  • CDC will also monitor adverse events following receipt of 2009 monovalent HINI vaccine using the Vaccine Safety Datalink (VSD). VSD is a collaborative effort between CDC and eight large managed care organizations (MCOs) representing approximately 3% of the U.S. population. The VSD uses rapid cycle analysis (RCA) to monitor specified adverse events in near real-time, using appropriate comparison groups. Adverse events of potential concern that are identified in VAERS or from other sources may be added to the 2009 H1N1 monovalent vaccine RCA study.
  • The Vaccine Analytic Unit (VAU) is a collaboration among the Department of Defense, CDC, and the FDA. It utilizes the Defense Medical Surveillance System (DMSS), which has data on ~1.5 million active US military personnel.  The VAU will monitor for adverse events after 2009 H1N1 monovalent vaccine using methods that are similar to those used in the VSD RCA study.
  • CDC will perform active Guillain-Barré syndrome (GBS) case-finding through the Emerging Infections Programs (EIP). EIP is a population-based network of CDC and 10 state health departments (CA, CO, CT, GA, MD, MN, NM, NY, OR, TN), working in collaboration with local health departments, public health laboratories, clinical laboratories, infection control practitioners, healthcare providers, academic institutions, and other federal agencies. CDC has also established collaboration with the American Academy of Neurology to enhance VAERS reporting of neurological events, including GBS. The provisional case definition for GBS from the Brighton Collaboration will be used.
  • The Clinical Immunization Safety Assessment (CISA), a collaboration between CDC and six academic centers with expertise in immunization safety, will provide clinical expertise and consultation in the evaluation of serious adverse events after 2009 H1N1 monovalent vaccine.

Suggested Planning Actions for Public Health Officials

State, local, tribal, and territorial health officials can enhance 2009 H1N1 monovalent vaccine safety monitoring through several planning activities. The following is a list of suggested planning activities for public health officials involved in vaccine safety monitoring. These may evolve as the vaccination program is implemented.

  • Be familiar with the VAERS reporting form and methods for reporting. Review the key information on the VAERS report form and understand how to submit a report. Clinically significant adverse events that follow vaccination should be reported to VAERS. Reports may be filed securely online, by mail, or by fax. Report forms are available online or can be obtained by calling 1-800-822-7967 to request reporting forms or other assistance. Healthcare and other reporters of adverse events should be encouraged, when submitting a report to VAERS, to include as much information as possible (e.g., vaccination location, date, vaccine type, lot number and dose); however, reports with incomplete information are accepted.
  • Identify and implement mechanisms to communicate vaccine safety information on a routine and urgent basis with healthcare and vaccine providers (defined broadly as those who provide vaccine in a range of settings, including retail-based clinics, workplaces, and urgent care centers), provider organizations, medical societies other partners and the public during the 2009 H1N1 monovalent vaccination response.
  • Initiate communications to increase awareness of VAERS. CDC encourages VAERS education for all healthcare providers (regardless of whether or not they participate in 2009 H1N1 monovalent vaccine vaccination) who may evaluate and treat patients with adverse events. VAERS education may be especially important for specialist physicians who may be less familiar with VAERS than providers who routinely order or administer vaccines. Providing information about how to report an adverse event to VAERS on the state or local health department website is encouraged.
  • Develop a plan to respond to vaccine safety concerns from providers and patients at the state and local level. This plan should include prompt reporting of clinically significant adverse events to VAERS and notifying CDC about reports of clusters of serious or unusual adverse events if state officials become aware of such occurrences. Public health officials with urgent vaccine safety public health concerns may contact CDC at 800-CDC-INFO (800-232-4636).
  • Identify staff that could assist in the event of a field investigation of adverse events following immunization. Staff in the 10 states participating in EIP could also work in collaboration with the EIP surveillance officers to enhance networking and communication with providers, particularly neurologists, in helping identify cases of GBS in their state.
  • Communicate the availability of vaccine cards and the importance of the information included on them to all vaccine and healthcare providers, the vaccinee, and other partners. CDC encourages the use of these cards, when available, throughout the state. CDC will design, process and package influenza vaccination cards that will be sent to vaccine providers at the same time 2009 H1N1 monovalent vaccine is distributed. These cards will contain space to document influenza vaccination location, date, vaccine type, lot number and dose. The cards will also be pre-populated with key information regarding an adverse event and how to report clinically significant adverse events to VAERS. The cards are intended to be given to the vaccinee (or parent or caregiver) at the first 2009 H1N1 monovalent vaccination visit for use during the influenza season. They should be kept by the vaccinee following their last influenza vaccine in the 2009-10 season.

CDC Support for Public Health Officials and Information about Vaccine Safety Coordinators

  • During 2009 H1N1 vaccine safety monitoring CDC will support public health officials involved with vaccine safety in the following ways:
    • Monitor the safety of the 2009 H1N1 monovalent vaccine vaccination program in the United States, in collaboration with FDA and other partners. CDC and FDA will have primary responsibility for analysis of VAERS data.
    • Provide technical assistance and support to state, local, tribal, and territorial health officials for 2009 H1N1 monovalent vaccine safety monitoring.
    • Manage an established collaboration between CDC’s Immunization Safety Office (ISO) and Vaccine Safety Coordinators positioned in all 50 states, the District of Columbia, eight U.S. territories5, and three major metropolitan health departments. CDC will be conducting regular meetings and vaccine safety training and education activities for the Vaccine Safety Coordinators during the pandemic (H1N1) 2009 response.
  • Vaccine Safety Coordinators are employed by the state or local health departments and may serve as liaisons between CDC and state or local health departments.
    • CDC encourages the Vaccine Safety Coordinators to establish collaborations with other state and local health officials involved in the 2009 H1N1 monovalent vaccination program, such as immunization and preparedness leads and immunization coordinators at state and local levels. The purpose of this collaboration is to help coordinate vaccine safety and related activities across the state or area. Vaccine Safety Coordinators may also identify senior staff in their jurisdiction that need to be informed and updated about key messages from CDC and other partners and know how to best communicate with these individuals.
    • The Vaccine Safety Coordinators will maintain frequent contact with CDC vaccine safety staff and may help to ensure adequate exchange of information, prompt response to vaccine safety emergencies, and optimal risk communication activities.
    • This close collaboration between CDC and state public health officials will help guide CDC’s vaccine safety activities to ensure they are best meeting the public health needs at the state and local level.


  1. An adjuvant is an additive to a vaccine that helps to generate a stronger immune response to the vaccine.
  2. CDC Prevention and Control of Seasonal Influenza with Vaccines Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009 contains information on seasonal influenza vaccine safety CDC. MMWR 2009; in-press
  3. In 1976, a type of influenza vaccine was associated with Guillain-Barré Syndrome (GBS). Since then, influenza vaccines have not been clearly linked to GBS. However, if there is a risk of GBS from seasonal influenza vaccines, it would be no more than approximately 1 additional case per million persons vaccinated.
  4. Reports of death, hospitalization or prolongation of hospitalization, life-threatening illness, persistent or significant disability/incapacity, or certain other medically important conditions are classified as serious
  5. The territories are: Puerto Rico, U.S. Virgin Islands, Guam, American Samoa, Commonwealth of Northern Mariana Islands. Freely-associated island jurisdictions: Palau, Federated States of Micronesia, Republic of Marshall Islands
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