Tuesday, October 03, 2006

Poliomyelitis- a disease that just will not go away

Poliomyelitis, an old disease strikes back

Dr Alex Tang

There had been high hopes that poliomyelitis or polio can be eradicated by the year 2000. The WHO has organized massive immunization programs and almost all countries use the WHO immunization schedule which includes vaccination against diphtheria, tetanus, and poliomyelitis. The Rotary Foundation has spent billions of dollars to ensure that children in the most remote areas receive the vaccine. With the combined might of the WHO and the NGO, the Rotary Foundation, there had been high hopes that poliomyelitis will go the way of smallpox.

Poliomyelitis cause paralysis of major muscles. In the old days, children with poliomyelitis have difficulty breathing as their respiratory muscles were paralyzed. They were placed in “iron lungs” which help them to breathe. The “iron lungs’ worked by alternately creating and releasing a vacuum.

In March 2005, a 20 months old boy was founded to be infected with a wild strain of polio virus in Girijaya village in the Sukabumi district of West Java. In spite of massive immunization of the Indonesian government, the outbreak resulted in 305 cases in 2005-2006 and claimed 6 lives. 47 districts and 10 provinces were affected. This virus was traced to its origin in Nigeria. It reached Indonesia via Yemen, Saudi Arabia and West Java. From there it spread to central Java, the Madera Islands and to Sumatra.

What went wrong? It was found that the polio vaccine coverage in Indonesia has dropped from more than 90% to 77.6% in 2005. Again, this is a reminder that we are fighting a holding battle against outbreaks of diseases like polio. We cannot afford to relax our vigilance.

There are two types of vaccines for polio. The Salk vaccine which is made up of the killed polio virus and the Sabin vaccine which is made from the weakened polio virus. Salk and Sabin are the names of two medical pioneers who did a lot of work on poliomyelitis. The Salk vaccine is given by injection into the muscles while the Sabin vaccine is given orally.

WHO made a decision to use the oral Sabin polio vaccine exclusively. The Malaysian Ministry of Health follows this decision religiously. However, there are two vaccine related problems with the oral polio vaccine which is not found in the injection polio vaccine.

First, it was found that the oral polio vaccine can cause polio! It was estimated that there are 400-800 cases of vaccine polio worldwide yearly. Vaccine polio can cause outbreaks; Hispaniola Islands in 2000, Indonesia in 2005 while the longest lasting was for 10 years in Egypt from 1983-1993.

Second, oral polio vaccine can cause paralysis. The muscles of affected children become flaccid. This condition is named vaccine associated paralytic polio (VAPP). It occurs in one per million does of oral polio vaccines.

One of the arguments against the use of injection polio vaccine was the “absence of herd immunity”. As the recent outbreaks in Indonesia shows, that argument is not longer valid since the polio outbreak occurs in spite of the community having “herd immunity’. Europe, Canada, South Korea, Australia, New Zealand, Japan and USA has all changed to injection polio vaccine in the last decade and there have been no significant outbreaks of polio reported.

The WHO recommends that the oral polio vaccine be discontinued as soon as polio was eradicated in 2000. It is now already 6 years past that dateline and we still have not eradicated the disease polio. Maybe it is time our Health Ministry should reconsider the WHO recommendation and make the decision to switch to injection polio vaccine independently. Most of the developed countries have already switched to injection polio vaccine.

The battle against polio has not been won. The polio vaccine has offered us an effective instrument to hold the disease at bay. Unfortunately the vaccine has created two new vaccine related diseases. The trade off is good but we could do better.



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