N. C. Grassly et al. have used logistic regression and found significant association between continued reporting of polio acute flaccid paralysis (AFP) and (i) population density, (ii) the prevalence of diarrhea, and (iii) low routine coverage with three doses of trivalent oral polio vaccine (tOPV) (1). This Week in Science (2) declares that Grassly et al. have shown that "high population density and poor sanitation are causing persistence by facilitating the transmission of poliovirus," as if a causal relationship has been established. Using the same logic, it may be said that (i) speaking the Bhojpuri language (3), (ii) living in a State through which the river Ganges flows, and (iii) the State capital having a maximum temperature of 24°C on 5 December 2005 (4, 5) are causing persistence of polio virus. The odds ratio of a State reporting more than 20 cases of polio AFP in 2006 (Uttar Pradesh and Bihar), if all three factors were present, was >999800. The associations we found were significantly stronger than that found by Grassly but that does not indicate that a cause-and-effect relationship has been established.
The article by Grassly et al. is an attempt to shift the blame for this poorly conceived program that has wasted millions of dollars and failed to deliver its promise of polio eradication. The polio eradication program started on the false premise that repeated doses of oral polio can by itself eradicate the disease worldwide (6). The failure of the “magic bullet” approach to solve the world's problems (repeated doses of OPV in this instance) was predictable.
The new study blames poor routine immunization against polio as one of the causes even though most of the cases that have developed polio have received more than 3 to 6 doses of tOPV, according to the admission of the authors. The problems of poor sanitation and overcrowding were well known before the program was started. Smokescreens must have no place in Science.
Sona Chowdhary and Jacob M. Puliyel
Department of Pediatrics,
St. Stephens Hospital,
Tis Hazari, Delhi 110054, India.
References
1. N. C. Grassly et al., Science 314, 1150 (2006).
2. S. Hurtley, P. Szuromi, Eds. Science 314, 1045 (2006).
3. http://en.wikipedia.org/wiki/Bhojpuri_language, Accessed 5/12/06.
4. http://www.wunderground.com/history/station/42492/2005/12/5/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA, Accessed 5/12/06.
5. http://www.wunderground.com/history/airport/VILK/2005/12/5/DailyHistory.html?req_city=NA&req_state=NA&req_statename=NA, Accessed 5/12/06.
6. C. Sathyamala, O. Mittal, R. Dasgupta, R. Priya, Int. J. Health Serv. 35, 361 (2005).
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