Centre says Meghalaya polio case is vaccine-derived

In rare cases, the weakened form of the virus in the vaccine can circulate in an under-immunised population, says WHO; less than 760 cases of vaccine-derived polio among three billion children immunised since 2000

Published - August 20, 2024 10:09 pm IST - GUWAHATI/NEW DELHI

Officials in Meghalaya’s West Garo Hills district are on high alert after the emergence of the latest case. Image for representation.

Officials in Meghalaya’s West Garo Hills district are on high alert after the emergence of the latest case. Image for representation.

A case of vaccine-derived polio has been confirmed in a two-year-old child from Tikrikilla in Meghalaya. A senior official from the Union Health Ministry official emphasised on Tuesday (August 20, 2024) that this is not a case of wild polio, but an infection that presents in some people with low immunity.

The World Health Organisation declared India polio-free in 2014 after the last case of wild poliovirus in the country was reported in 2011.

High alert

Officials in Meghalaya’s West Garo Hills district are on high alert after the emergence of the latest case. “The two-year-old child from Tikrikilla was found to have symptoms of poliomyelitis more than a week ago. The child was diagnosed with acute flaccid paralysis at a hospital in Assam’s Goalpara,’’ Chief Minister Conrad K. Sangma said.

Health officials in Meghalaya said that stool and other samples collected from the child were sent to testing centres in Kolkata and Mumbai run by the Indian Council of Medical Research’s National Institute of Virology.

“We are still examining the issue. It is a very serious situation that will be reviewed soon,” Mr. Sangma told journalists in the State’s capital Shillong on the sidelines of an event.

Rare complication

The oral polio vaccine (OPV) contains an attenuated or weakened form of the virus, which activates an immune response in the body. 

During this time, this vaccine-virus is also excreted. On rare occasions, if a population is seriously under-immunised, an excreted vaccine-virus can continue to circulate for an extended period of time. The longer it is allowed to survive, the more genetic changes it undergoes. In very rare instances, the vaccine-virus can genetically change into a form that can paralyse. This is what is known as a circulating vaccine-derived poliovirus (cVDPV), according to the WHO.

Since 2000, more than 10 billion doses of OPV have been administered to nearly three billion children worldwide. During that time, 24 cVDPV outbreaks have occurred in 21 countries, resulting in fewer than 760 VDPV cases.

Immunisation is key

“Circulating VDPVs in the past have been rapidly stopped with two to three rounds of high-quality immunization campaigns. The solution is the same for all polio outbreaks: immunize every child several times with the oral vaccine to stop polio transmission, regardless of the origin of the virus,’’ the global organisation notes.

The symptoms of poliovirus can include fatigue, fever, headache, vomiting, diarrhoea or constipation, sore throat, neck stiffness, pain or tingling sensations in the arms and legs, severe headaches, and sensitivity to light (photophobia).

The virus typically causes acute and short-term infections, with infected individuals capable of transmitting it for less than two weeks in most cases. Humans are the sole reservoir for the virus, and there is no vector involved in its transmission.

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