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BART ROMBAUT AN. R. ACAD. NAC. FARM.

TABLE 2. Inactivation mechanisms of thermolabile OPV

One of the main problems with OPV (already discussed in a
previous section) is its thermolability. OPV is the least thermostable
vaccine of the six antigens provided by the nationale routine
immunization. A «cold chain» is required to bring the vaccine to the
vaccinees. This «cold chain» might be a problem to realize in
developing tropical and subtropical countries. The final step of the
eradication of poliovirus, the «mopping-up» component will be more
difficult to realize if the vaccine must be strictly maintained within
narrow temperature limits. Therefore, WHO prepared in 1989 a
request for proposals in order to enhance the thermostability of
OPV. Research as an answer to this request, revealed that the
thermolability of the vaccine is due to two different inactivation
mechanisms: (i) denaturation of the viral capsid and, (ii) degradation
of the viral RNA within the capsid (26, 27) and that chemical tools
are available to stabilize both mechanisms (27, 28). However, a few
years later, WHO decided to abandon all work on new or improved
vaccines. After the succes of eradication polio in the Americas, WHO
made the decision to globally eradicate poliovirus with OPV.

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