CSU 5/2008: POLIO COMPARED TO MEASLES/ACPE PRESENTATION/WHO
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
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
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
"[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."