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Polio vaccine choices

Published May 12, 2014 07:40am


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WHEN I think of the reaction of state and society over the polio-related travel restrictions recommended by the World Health Organisation last week, in my mind’s eye I get the picture of Chicken Licken running around, worried about the sky falling on its head.

That is, of course, if the issue wasn’t so frighteningly serious. Pakistan remains one of the three lone countries, the others being Afghanistan and Nigeria, that are still polio-endemic; far from bringing the spread of this virus under control, we actually seem to be seeing some sort of resurgence. As for the acts of aggression visited upon polio teams and their armed guards, the less said about them, the better.

Bottom line: not just are Pakistanis themselves under an increased risk of becoming carriers of or contracting the disease, we are in danger of re-infecting the planet.

Think about that for a second: the world, much of which has succeeded in cleaning up its house with regard to polio, stands in danger of being re-infected because of Pakistan. Think of the thousands of Pakistanis that go to and from other countries, any one of them, or any ten of them, or any hundred of them, a possible carrier of the virus.

The possibility of travel restrictions was introduced in 2011, by the Independent Monitoring Board for Polio Eradication. We’ve had years in which we could have cleaned up our act, and we didn’t.

Despite the hullaballoo, though, there still doesn’t seem to be sufficient understanding of how this virus spreads, who is at danger, and what should be done, even though some of the challenges are obvious.

First, person-to-person spread of the poliovirus occurs through the fecal-oral route, and sometimes oral-to-oral.

Second, polio is an illness with an affinity for children, but adults can get it. It’s rare, but it’s possible.

Two kinds of vaccinations are available. There is the Oral Polio Vaccine (OPV), which is a live virus delivered via the mouth. It is very efficacious, and according to the Centre for Disease Control “probably” provides a lifetime of safety. But, with the OPV, there is a risk — very small, but there nevertheless — of a person contracting the disease because of the administration of the vaccine, called the vaccine-associated paralytic polio (VAPP).

The numbers are fractional: in the US, where the last case of wild-virus polio was in 1979, from 1980 to 1999, VAPP accounted for 95pc of all cases of paralytic poliomyelitis, which eventually led to the administration of the OPV being replaced in 2000. But, to put that in perspective, between 1980 to 1994 in the US, according to CDC data, 303 million doses of OPV were distributed and 125 cases of VAPP were reported.

VAPP is more likely to occur in persons above the age of 18, and is much more likely to occur in immunodeficient children. With certain sorts of immunodeficiencies, the risk of VAPP can be thousands of times higher.

The way around VAPP is the Inactivated Polio Vaccine, or IPV, in which the polio virus has been killed off with formaldehyde. This is injected, there’s no risk of VAPP, and therefore it’s safe for adults. But the duration of the immunity is not known with certainty. The IPV is the standard in much of the world because the assumption is that people will not risk exposure.

But why would world polio bodies be recommending the OPV for immunisation when there’s the risk of VAPP?

The answer is a hard one. The only way to eradicate polio on a mass scale is through the OPV, which is cheaper, easier to administer, and in any case refers primarily to children, who are less liable to contract VAPP. All countries that have eradicated polio have done so with the OPV, and those that have switched over entirely to the IPV have done so after eradication, when exposure is likely to be minimal. In other words, the risk to some few individuals that may contract VAPP must be taken in view of the greater good of the population at large. WHO, or other global bodies care less — as they should — about your or my right to be protected from VAPP when there’s the whole population, the whole world, to be protected.

Pakistan is unique in that this is the only place that is seeing the risk of polio exposure increasing. Medical research is mainly predicated on either progress being made towards the reduction of polio, or eradication.

Regardless of travelling, all of Pakistan’s children need vaccination, and given the risk, so do adults. But they should be aware of the risks — however small — associated with adults having the OPV.

The writer is a member of staff.

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