[Emerging Infectious Diseases]                                                         
[Volume 4 No. 3 / July - September 1998]

Special Issue

Vaccine-Preventable Diseases

Alison C. Mawle
Centers for Disease Control and Prevention, Atlanta, Georgia, USA

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The panel addressed four main areas of vaccine development and use:
diseases of public health importance for which no vaccine is available;
diseases for which an existing licensed vaccine is not optimal and
alternative vaccines are under development; diseases for which a vaccine
exists but is not being used optimally; and diseases requiring vaccines of
specialized or limited use, such as those needed for controlling outbreaks
or for military use. The specific diseases chosen to illustrate each area
were malaria, influenza, meningitis, and filovirus infections (Ebola and
Marburg), respectively.

Lee Hall, National Institute of Allergy and Infectious Diseases, addressed
the basic challenges in developing a malaria vaccine. The historical norm
of vaccine development has been an empirical process; in contrast, modern
vaccines take advantage of basic knowledge of the organism and of the
immune response to it. In vaccine development, certain elements are
prerequisite: demonstrable protective immunity and intimate knowledge of
the organism's life cycle, including the DNA sequence. Vaccine development
has three potential goals: prevent infection, prevent disease, and prevent
transmission. A successful vaccine may address any or all these areas; for
malaria, a vaccine able to perform any of these would have a significant
impact. Vaccine development, often thought of as a flow, is in fact an
iterative process; it addresses scientific, technical, manufacturing, and
clinical issues and is affected by economic, political, and social issues
usually outside the scientific sphere of influence. Several downstream gaps
in vaccine development include resource limitation, lack of
standardization, and problems in clinical and industrial interest.

Claude Hannoun, Institut Pasteur, addressed problems in influenza vaccine
development. Influenza, the quintessential emerging infectious disease,
needs a new vaccine each year to protect against the predominant strains.
The disease poses additional challenges; one is the need for vaccine
against a potential pandemic strain, particularly a pandemic strain whose
epidemiologic characteristics are different from those of usual strains
(e.g., the 1918 strain killed young adults). Vaccine production problems
pose another challenge. Identifying an appropriate seed strain can delay
initiation of production for 4 to 6 months after the need for a vaccine has
been identified, and growing sufficient quantities of vaccine is difficult.
The issue of an appropriate vaccine regimen (one dose or two) was also
addressed. The many vaccination issues involved in a pandemic situation
make the adoption of a credible pandemic plan imperative. The emergence of
the H5N1 strain in Hong Kong has underlined this imperative.

Brad Perkins, Centers for Disease Control and Prevention, presented the
challenge of the African meningitis belt, where periodic large epidemics
affect approximately 1% of the population with a 10% death rate. Since the
current vaccine does not confer lasting protection, prediction of these
epidemics can trigger vaccination campaigns to prevent deaths. A model
using an epidemic threshold of 15 cases per 100,000 demonstrated potential
lives saved. Obstacles to the use of the vaccine include inadequate
surveillance, high cost of the vaccine, inadequate delivery systems, and
inadequate vaccine supply.

Vaccines for agents such as Marburg and Ebola were discussed by Alan
Schmaljohn, U.S. Army Medical Research Institute of Infectious Diseases.
Limited-use vaccines do not have a global market but are potentially
important against the threat of biological weapons or epidemics. These
vaccines have unique problems, such as inadequate efficacy testing (since
there is no disease-endemic area) and high production costs (since there is
no target population).

All the presentations addressed public policy issues: who will use the
vaccine and under what circumstances, what is the time frame for vaccine
development (short-term versus long-term), what is the cost of a vaccine
(who bears the brunt of development costs), how are these costs recouped,
and what is the role of partnerships in determining vaccine need and use.



Emerging Infectious Diseases
National Center for Infectious Diseases
Centers for Disease Control and Prevention
Atlanta, GA

URL: ftp://ftp.cdc.gov/pub/EID/vol4no3/ascii/mawl.txt

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