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POLIO COMPARED TO MEASLES

Monday, 4th of February 2008

 CSU 5/2008: POLIO COMPARED TO MEASLES/ACPE PRESENTATION/WHO
 POLIO RESOLUTION
 
 
 1) RESPONSE TO READER QUERY: POLIO COMPARED TO MEASLES
 
 In the first update of 2008, I asked readers for their views on the
 similarities and differences between polio and measles in terms of
 eradicability.
 
 From Professor Samuel Katz, Duke University, comes an unequivocal reply,
 reproduced here in its entirety.
 
 "Measles and polio differ significantly so that elimination/eradication
 issues are totally different.
 
 Measles is nearly always an overt infection (signs and symptoms) whereas
 polio may have 200 or more occult infected individuals for the one with
 signs and symptoms.
 
 Measles virus is excreted and transmissible during late incubation and
 early disease (a week more or less) while polio is excreted and
 transmissible for 3-4 weeks.
 
 Measles is a stable virus with no significant genetic changes in more than
 45 years; polio vaccine viruses mutate significantly and rapidly so that
 circulating vaccine-derived viruses have become a problem.
 
 Measles is the most highly transmissible of any of the virus infections so
 that nearly 100% of susceptibles must be immunized to eliminate
 transmission, whereas polio though readily transmitted does not have as
 high a degree of transmissibility.
 
 Measles vaccine with 2 doses immunizes nearly 100% of susceptibles after
 age 9 months, whereas polio vaccine has far less efficacy in many
 populations, requiring a minimum of 3 or 4 doses and in some settings
 (India for example) a dozen or more.
 
 Polio vaccine can be started successfully as early as 2 months of age,
 while measles is ineffective before 6-9 months of age (because of residual
 maternal transplacental antibodies)."
 
 To these points, I would add the following observations:
 
 1) there is a strong preference in many cultures for items given by
 injection. This tells in favor of the  parenterally administered vaccines, despite the operational headaches
 of training, sharps disposal, etc.
 The preference for injections may help to explain the dearth of rumor
 campaigns against the measles shot in
 most developing countries, whereas antivaccination rumors have in
 some countries been the bête noire of polio eradication.
 
 2) the last two decades have seen the following obstacles to measles
 elimination removed: i) no auto-disabled
 needle/syringe combination; ii) no vaccine vial monitor iii) no
 agreed policy for overcoming the 10-15 percent
 failure rate for vaccinations given once at 9 months, iv) no credible
 proof of concept at the regional level;
 v) no global partnership to harmonize the contributions of different
 stakeholders vi) no decisions by WHO
 regional governing bodies in favor of timebound regional elimination
 targets.
 
 Is the time ripe for a global war on measles?
 
  
 2) WHO EXECUTIVE BOARD ON POLIO ERADICATION
 
 W.H.O.'s Executive Board, meeting in Geneva this week, proposed for WHA
 approval a draft resolution on polio eradication.
 
 The Board accepted the proposed Secretariat draft in full, adding the
 following text.
 
 "[the Executive Board requests the Director-General] to develop a new
 strategy for renewed fight to eradicate poliomyelitis from the remaining
 countries drawin on experience from regions where poliomyelitis is
 eradicated and on operatoins research in order to determine the most
 efficient and cost-effective interventions."
 
 
  Good reading.
 
 BD