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PRODUCT WATCH
One dose of life
 To ensure the
success of the polio eradication programme, a new vaccine — the "monovalent oral
polio vaccine" (mOPV) — to fight the type 1 strain of polio virus is being
introduced. The polio virus transmission still persists in the Indian slums. According to
Brent Burkholder, acting regional advisor, vaccines and other biologicals, World Health
Organization-Regional Office for South East Asia (WHO SEARO), the decision to introduce
the monovalent vaccine is waiting for the final approval of the secretary, ministry of
health and family welfare. He said the vaccine will be given to the people in the areas
where the type 1 virus is more prevalent, particularly after spring.
The type 3 virus is known to strike after September. Type 2 virus has been eradicated,
while the type 3 is still prevalent, but not largely so. Type 1 virus is the most lethal
followed by type 3. This fact prompted the introduction of mOPV against the type 1 polio
virus that leads to paralytic polio. In Mumbai, 84 environmental samples tested positive
for the above virus in 2004. "Data from five tropical countries shows that just one
dose of mOPV conferred immunity in 81 per cent of those vaccinated," says Ronald
Sutter from the Centre for Disease Control and Prevention, USA. This is in contrast with
30-40 per cent immunity rate conferred by one dose of present trivalent OPV. This is
because the live and dormant virus that replicates in the gut does not have to compete
with the other two virus types of cells susceptible to infection. "At this stage, the
benefits of the vaccine are only theoretical," opines Bruce Alyward, who coordinates
the polio eradication programme from WHO. Two companies — Sanofi Pasteur in Lyon,
France and Delhi-based Panacea Biotech — are going todeliver 200 million doses. But
because mOPV has not been produced by any company in years, it is no longer licensed. So
the vaccine has to be reviewed as a new product. If the vaccine is ready by May 2005, as
planned, there should be delivery of at least two rounds in parts of India before the
beginning of the peak season of viral transmission, from July to September.
Another concern is that the promise of a more effective vaccine might divert attention
from the need to reach every single child with doses of the type 3 OPV, which needs to be
continued. According to WHO, in 2004, the number of type 1 polio virus cases was 129 as
compared to seven type 3 polio virus cases. Thus, it is logical to increase the number of
vaccine polio viruses type 1 in OPV. But the noteworthy fact is that type 3 polio virus
was also found in places like western Uttar Pradesh where type 1 is present. Hence,
focussing only on the type 1 polio virus could lead to the ignoring of the other virus
that is still not totally eradicated. It is very important to plan the initiation of mOPV
administration, taking into consideration all these vital factors. |
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