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
�