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The right combination
immunize against several diseases at once have obvious advantages.
But how many are available for use in developing countries?
Lisa Jacobs finds out
THE more diseases an immunization
programme can prevent, the better: few health officials would
argue with that. But every addition of a separate new antigen
into a vaccination schedule requires another shot, another
needle and syringe, and extra disposal costs. And, just as
important, the extra responsibility on over-burdened health
systems may also increase the risks of unsafe injections.
In light of this, the GAVI Board made the decision
that for those eligible countries that seek to introduce
vaccines against hepatitis B and/or Haemophilus influenzae
type b (Hib) the vaccines purchased by the Vaccine Fund
for Childrens Vaccines should be combination vaccines.
However, there are comparatively few of these combinations
The most widely used
combination in developing countries is the vaccine against
diphtheria, tetanus and pertussis, known as DTP*.
Under pressure: busy health workers
jobs would be simplified with combination vaccines
Because of its widespread
use, ease of administration, and three-dose schedule given
in infancy, it has become the foundation of routine immunization
coverage. DTP has also become the foundation upon which many
of the existing combinations have been built, including those
relevant to GAVI:
(formerly Smithkline Beecham) has combined DTP with
hepatitis B in a four-antigen (tetravalent) vaccine;
(formerly Pasteur Mérieux Connaught) has combined
DTP with Hib;
has combined DTP with both hepatitis B and Hib. This
is actually a combination of tetravalent DTP-hepatitis
B and freeze-dried Hib that needs to be mixed by the
health worker at the time of injection.
No combination vaccines
currently incorporate yellow fever. This is likely to
remain a single-antigen vaccine.
Part of the reason why the
list is so short is that many high-income countries are not
interested in buying vaccines that contain whole-cell pertussis,
preferring instead the acellular pertussis (DTaP), despite
its higher price. This reduces the incentive for companies
to develop combinations containing the whole-cell preparation.
A full load: every vaccine must be
transported and kept cold; more separate antigens would
strain the system
in the public health community worry that, because of
the comparative lack of competition, combination vaccines
will never be as affordable as single-antigen vaccines.
On the face of it, the combination vaccines do look more
expensive: for example, DTP combined with hepatitis B
may cost up to US$1.07 per dose, including the cost of
an autodestruct syringe, while DTP and hepatitis B can
be given separately for US$0.80, including the cost of
two autodestruct syringes.
But these concerns
about cost are dismissed by Steven Jarrett, procurement
manager for UNICEF, which supplies many developing countries
with vaccines and injection materials.
"My calculation is that when you take all costs into account
logistics, labour, compliance issues and the risk of unsafe
injections combination vaccines are definitely not more expensive
than individual antigens," he says.
Furthermore, as more of these vaccines
are purchased for the developing-world market, prices could
drop. There are precedents: when it was first introduced,
Hepatitis B cost US$25 per dose; now it is well under US$1.
And as recently as 1998, Latin American countries were purchasing
Hib vaccine directly from manufacturers for as much US$8.50
per dose. Now the Pan American Health Organization is able
to offer the vaccine to its member states for US$3.00 per
dose, according to estimates for the year 2000. As demand
for these new and under-used vaccines increases, more companies
may enter the market.
The process may take some time,
however. Combining existing antigens is not a simple development,
but poses complex technical and clinical challenges, since the combined
product has to demonstrate equivalent safety and immunogenicity.
New combination vaccines must undergo extensive clinical trials
to ascertain whether the different components, including the individual
antigens, stabilizers and preservatives, have had negative effects
on efficacy. The regulatory process alone can take three to five
years, and adds to vaccines cost.
"There is no way to avoid
combination vaccines in the future and we should be prepared
to have more and more of them," says Jacques-François
Martin, CEO of Parteurop. "But making things easier also makes
things more complicated. A company that holds the market position
today could lose everything tomorrow if it does not include
a particular antigen in its combinations. Market forces will
no longer be able to dictate future vaccine needs. We will
have to agree on certain orientations today in order to provide
the world with vaccines they can use in the future."
*Two versions of DTP are
available: the whole-cell pertussis and acellular pertussis
(DTaP), approved for use because of minor side effects that
can occur with whole-cell pertussis.
Lisa Jacobs is Communications
Officer for the GAVI Secretariat
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