Over 4.9 lakh persons in India developed paralysis between 2000 and 2017 because of oral polio vaccine (OPV), say leading doctors in two reputed hospitals here.
Jacob Puliyel, a paediatrician at St. Stephen’s Hospital, and his co-workers claim their study has shown that “frequency of pulse polio administration is directly or indirectly related to incidence of non-polio acute flaccid paralysis [NPAFP]”.
WHO recommendation
Their study, which calls for judicious use of the OPV schedule to prevent vaccine-induced paralysis, has been published in the International Journal of Environmental Research and Public Health . The Union Health Ministry is yet to respond to the issue.
To monitor the progress of polio eradication, the World Health Organization (WHO) recommends that countries conduct surveillance for cases of acute flaccid paralysis (AFP).
Acute flaccid paralysis
AFP is defined as a sudden onset of paralysis or weakness in any part of the body of a child less than 15 years of age. The surveillance allows nations to detect paralytic poliomyelitis due to wild poliovirus transmission in the population. There are many causes of AFP, so each case needs to be evaluated to find out if the paralysis is due to polio or not. This investigation includes testing stool specimens of all cases for detection of the polio virus.
More than 50,000 AFP cases are investigated in India every year as part of this surveillance system, which has been in place since 1997. In 2009, 741 of these AFP cases in India tested positive for polio. In 2010, only 42 cases tested positive, while in 2011 only a single AFP case tested positive for polio. Not a single AFP case tested positive for polio in 2012, 2013 and 2014. All AFP cases during the last three years have been due to non-polio causes.
“These are all cases of non-polio paralysis, which increased dramatically as polio paralysis was brought down with repeated doses of OPV. This report shows that the rate of paralysis is now coming down where OPV doses have decreased and this is additional proof that paralysis is caused by OPV,” says Dr. Puliyel.
Last case of polio
The last case of polio in the country was reported in 2011, but India, even after it was certified polio-free, maintains its surveillance system in order to pick up any imported cases of polio. In the absence of wild polio transmission, it is expected that AFP cases in India will reduce to an acceptable rate of around two in 1 lakh cases.
“Although surveillance in India has been exemplary, this has not yet materialised,” the report says.
AFP rate in some States is as high as 30 in 1 lakh persons. The present study — using surveillance data obtained from all 36 States and Union Territories — was done to see if the incidence of NPAFP declined with reduction in pulse polio immunisation rounds.
‘High correlation’
The results, however, showed that the number of pulse polio rounds conducted in a State had “high correlation” with NPAFP rate in a State. NPAFP rates in Uttar Pradesh and Bihar were the highest in the country.
“Our study found that NPAFP rate in these States was high in those years when the number of pulse polio rounds conducted was high,” the researchers say.
For instance, there were an additional 47,500 children with paralysis in 2011, which was over and above the assumed NPAFP rate of 2 per 1 lakh cases and the NPAFP rate started to decrease from 2012, when the number of pulse polio rounds decreased.
“From the results, NPAFP rate shows a decline with reduction in pulse polio doses suggesting that OPV vaccinations are responsible for the paralysis. A total of 6.4 lakh children developed NPAFP from 2000 to 2017, suggesting that there were an additional 4.91 lakh paralysed children above the numbers expected to develop NPAFP,” they add.
The report says that “repeated doses of live vaccine virus delivered to the intestine may colonise the gut and alter the viral microbiome of the intestine”.
Also, studies from Finland and Turkey suggest that Guillain-Barré Syndrome (GBS) is causatively associated with OPV vaccination campaigns
“While the mechanism involved is speculative, our findings support the hypothesis that the frequency of pulse polio administration is directly or indirectly related to the incidence of NPAFP. Now that India has been polio-free for over six years, we may be able to reduce NPAFP by further reducing pulse polio rounds,” the report says.
OPV administration
Commending the government for its enormous efforts towards polio eradication, the researchers hope their observation “will help at optimising the dose schedule of OPV administration” to prevent paralysis in vaccinated children.
Dr. Puliyel’s team included Rachana Dhiman and Sandeep Prakash of St. Stephen’s Hospital, and V. Sreenivas of the All India Institute of Medical Sciences.
