Listen to Story A case of polio has been confirmed in a two-year-old child from West Garo Hills district in Meghalaya. The development has raised concern has India was declared polio-free by the World Health Organisation (WHO) in 2014 after the last case was reported in 2011. The health ministry said that this is not a case of wild polio, however, but a case of vaccine-derived polio , in which an infection presents in people with low immunity.
The WHO has been alerted about the case and an investigation is underway. The WHO doctors arrived in Tikrikilla to collect the samples. WHAT IS VACCINE-DERIVED POLIO? Poliomyelitis, or polio, is a highly infectious disease caused by the poliomyelitis virus.
It is usually transmitted through the faecal-oral route, typically by ingesting contaminated water or food. It is a highly contagious virus that can lead to paralysis. 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, also known as photophobia.
There are three types of poliovirus: wild poliovirus type 1 (WPV1), wild poliovirus type 2 (WPV2) and wild poliovirus type 3 (WPV3). Symptomatically, all these strains are identical. The cases of polio that have been seen historically have generally been of wild poliovirus.
In 1988, the Global Polio Eradication Initiative was launched for equitable vaccine administration. While India was declared polio-free in 2014, only 12 cases of paralysis caused by wild poliovirus were reported from just two countries: Pakistan and Afghanistan. However, while the number of wild poliovirus cases decreased, there was another type of polio cases that increased: vaccine-derived .
TYPES OF POLIO VACCINES There are two types of polio vaccines: one is given orally and the other by injection. Oral Polio Vaccine (OPV): This is the most commonly administered vaccine in India. OPV contains a weakened form of the poliovirus, which helps to stimulate an immune response without causing the disease.
It is administered orally, typically in drops. OPV is used in mass immunization campaigns, such as the National Immunization Days (NIDs). Inactivated Polio Vaccine (IPV): IPV contains an inactivated (killed) version of the poliovirus and is administered via injection.
IPV is included in the routine immunization schedule in India and is often given alongside other vaccines in combination shots. In India, both types of vaccines are administered. OPV is usually preferred because of the ease of administration.
Since the oral polio vaccine uses a weakened form of the virus, which doesn't cause disease, it can still replicate. A very rare but adverse side effect of OPV is vaccine-associated paralytic poliomyelitis (VAPP), which is may not be caused by IPV. After OPV, the vaccine virus which is shed in the stool can spread to others, causing vaccine-derived polio.
Over time, this virus can mutate and potentially circulate, causing paralysis in communities with low immunity levels. According to the US Centre for Disease Control and Prevention (CDC), in 2023, 524 polio cases across 32 countries were linked to vaccine-derived poliovirus..
