Indigenous
measles has been eliminated or nearly eliminated in several countries, Finland
being among first ones outside archipelago (Cuba in The Caribbean) or otherwise
isolated regions. This elimination was achieved by systematic two-vaccine-dose
regimen of children, and now it seems clear that more than one dose is needed
for the elimination of this extremely contagious infection. Mathematic models
suggest that the vaccination coverage should be around 95% to get rid of
indigenous measles. Now that the measles elimination is demonstrated, the
question is if the virus also is eliminable, or preferably, eradicable. If so,
measles can be eradicted globally.
In principle, the eradication of measles is possible ; in fact, it is a distant target of WHO. At least five reasons stand for such an optimism. First, virtually Man only is prone to measles ; no animal reservoir exists. Second, measles infection leads to symptoms and signs which makes the diagnosis fairly reliable (opposite to e.g. rubella) . Third, a safe, sufficiently immunogenic and not too expensive vaccine that induces long-term protection is available. Fourth, protection can be achieved during the incubation period, and vaccination (earlier, immunoglobulin) may be used even in the epidemic conditions. Taken all these factors combined the implication is that one can get rid of measles and its causative agent, provided the circulation of virus is interrupted globally.
However,
in 2001 we are very far from that target. Several realities of our everyday
life do not favor worldwide
success. First, measles is too contagious to be easily prevented – few
countries reach a ≥95% vaccination coverage. Second, the vaccine is
thermolabile and requires a functioning cold-chain system. Third, once the
incidence of measles has declined
significantly (thanks to vaccination), the risk of vaccine failures
increases because measles outbreaks here and there do not more booster the
antibody levels ; waning immunity is a reality of increasing importance in
areas with high vaccination coverage. Fourth, antivaccination lobbies in
several countries have done their work well and decreased the number of
vaccines. Fifth, various human catastrophies, so common in the poorest areas of
the world, pose another snag for measles eradication.
Measles,
as many other infectious diseases, is tightly bound with the behavior of Man,
and when you have to deal with the human behavior, troubles are numerous. On
the other hand, successful elimination of indigenous measles in some regions
shows that eradication of this virus is worth trying.