H1N1 COUNTERMEASURES STRATEGY AND ... - PHE Home

NBSB Pandemic Influenza Working Group
Detailed Report
important to distinguish adverse events from conditions that would have occurred without
immunization given the normal background rates. To illustrate his point, Dr. Salmon
referred to spontaneous abortions. Given the current background rate of approximately
15% of clinically recognized pregnancies resulting in a spontaneous abortion
(miscarriage), it is likely that with 50% vaccine coverage of all pregnant women, there
would be about 1,200 spontaneous abortions within 24 hours of vaccination due entirely
to chance. In the event of mass vaccination, an otherwise random event will not be seen
as random, especially if and when adverse events occur in clusters.
The following infrastructure are in place to support vaccine safety monitoring:
VAERS is a passive surveillance system operated by the CDC and FDA that
accepts reports from any source. Its limitations include likely underreporting and
incomplete data. VAERS can be helpful in detecting signals or generating
hypotheses but can not assess causality. It’s a national database that can look at
vaccine-specific events and subpopulations.
VSD is a large database of information from eight managed care organizations,
operated by CDC, that includes exposure data (including vaccine histories), lot
numbers, and complete patient medical records. It is useful for testing hypotheses
but is limited by the small numbers of patients represented (3% of the U.S.
population).
CDC’s Clinical Immunization Safety Assessment (CISA) Network is used to
investigate pathophysiological mechanisms and biological risks for adverse
reactions. It incorporates VAERS data and can be used to develop clinical
guidance.
The DoD uses a number of systems, including VAERS, that involve both passive
and active surveillance. The Military Vaccine Reporting System provides an
option that allows a health care provider to follow up on the report.
The Department of Veterans Affairs (VA) monitors events through its Adverse
Events Reporting System and conducts active surveillance of influenza and
pneumococcal vaccines in collaboration with FDA. It is developing rapid-cycle
analysis techniques.
The NVPO’s summary document, Comprehensive Review of Federal Vaccine Safety
Programs and Public Health Activities, is available online at
http://www.hhs.gov/nvpo/nvac/documents/ vaccine-safety-review.pdf.
The challenges of safety monitoring for H1N1 include the number of uncertainties about
the formula, dosages, use of adjuvant, distribution, and prioritization. Will those
vaccinated first be captured under current surveillance systems? What other mechanisms
are available for surveillance?
Dr. Salmon said the key challenges of evaluating the data include linking exposure and
outcomes data, particularly if the vaccine is not delivered through the health care system.
The database of the Centers for Medicare and Medicaid Services (CMS) could be useful
if it can identify who was vaccinated. When pregnant women are vaccinated, it may be
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