28 June 2010

Past time to pay attention to polio

This is an addition for archival purposes of a post that originally appeared at Scienceblogs.

In the winter of 1999, I stood in an outpatient clinic in a pediatric hospital in New Delhi and listened to a father sobbing over the paralysis of his only son. He was a farmer and lived in Uttar Pradesh; counting walks, minibuses and trains, it had taken him 24 hours to get to the hospital. He had carried the toddler the entire way.

His son had gotten the drops, he insisted: Every time the teams came to his neighborhood -- which they did three, four times each year -- he or his wife had lined up all their children, the boy and his older sisters. His son had had 11, 12 doses, the man said. How could he have gotten polio? And it was polio, the doctor treating him confirmed, not one of the transient febrile paralyses that exist alongside the disease and make detection and diagnosis so complex in resource-poor settings. She saw this all the time, she confided. The massive polio-eradication campaigns that continually blanketed India had trouble reaching some resistant populations, and those children contracted polio because they were not vaccinated -- but children whose parents were compliant, who believed in the drops and made sure their children received them, became paralyzed as well.

I was in India that winter because the long-hoped-for goal of the worldwide eradication of polio was supposed to be achieved the following year, in 2000. The global eradication initiative -- led by the WHO, the CDC and a massive volunteer effort by Rotary International -- didn't make that goal that year. Or in 2002, or in 2005. For a variety of reasons, from the biology of the disease in the tropics to political manipulation in service of unrelated ends, several countries have remained stubborn hot spots. And as long as the disease persists within their borders, it can leak outside them and become re-established in any area where vaccination has slowed down because the goal of stopping local transmission appears to have been achieved.

Most recently, it has leaked to Tajikistan, a country that has been polio-free since 2002 but shares borders with three of the four countries -- India, Pakistan and Afghanistan (Nigeria is the fourth) -- where polio remains endemic. As of the last count, 183 children were confirmed to have polio; authorities generally estimate that for every child detected with polio, 200 others may be infected silently and can pass on the disease.

There is so much to say about polio eradication; it is an impossibly complex and expensive task, fraught with cultural complexities and burdened with an endgame of clean-up that will stretch years beyond eradication itself. It is so complex that major public health figures have periodically thrown up their hands and declared eradication unachievable. It is one of the most expensive public health campaigns every attempted, with billions spent so far (and yet chronically short of funds). And because most of the West remains fully vaccinated, polio lurks far below the radar horizon of our concern.

I say all this -- which is kind of opening the floodgates for me, because I've wanted to talk about polio for years, but it is a damn hard story to sell to editors -- because CMAJ, the Canadian Medical Association Journal, has published a great editorial calling for the West to take the threat of polio seriously again.
Although the rates of poliovirus immunization in most of Europe exceed 90%, neither the Ukraine nor Georgia has reached this target. Furthermore, regions of Canada and some European countries have very low rates of vaccine uptake. Infants and toddlers are often not vaccinated on time because of a lack of appreciation of the seriousness of poliomyelitis. Community immunization rates may also be adversely influenced by concerns about vaccine safety, religious beliefs barring vaccination and antivaccine or antigovernment sentiments... There are no cures for poliomyelitis -- prevention through vaccination is our best and only defence. We are only one asymptomatic infected traveller away from an outbreak because of low vaccination rates. (MacDonald and Hebert)

Since the year 2000, there have been two recurrences of polio in the US: one in Minnesota, sparked by the vaccine virus, and one in Arizona contracted by a college student traveling abroad. The college student, and the children in the Minnesota community, had never been vaccinated because of religious or cultural exemptions. So our protections are not as impermeable as we think.


Anonymous said...

Maryn, could you please talk about the serious problem of children repeatedly vaccinated with the OPV, but who do not mount an immune response?

(The gut reaction / lack of reaction etc.)

Maryn McKenna said...

Absolutely, I'll put it on my list. It's a fascinating and difficult topic.