Inactivated polio vaccine (IPV)
Polio was a leading cause of permanent disability in children in past. Poliomyelitis is a disease spread by poliovirus type 1, 2, 3. After world wide introduction of polio vaccine in national immunization schedules of the many nations, now polio is a disease shortly going to extinction. It is huge success of vaccination campaign by all governments. Still in some pockets of the world still some sporadic cases are reported due to inadequate coverage and acceptance of the vaccination.
About poliovirus
Poliovirus is a member of Picornaviridae family of viruses. Poliovirus is of 3 types, type 1, type 2, type 3. Type 1 and 3 were possible for maximum number of endemic cases. It is single stranded RNA virus. It is non enveloped virus.
How does poliovirus spread?
Poliovirus spread by contaminated water by feco-oral or oro-oral route. Mainly affects the children below 5 years old. 0.5 percent children of those who get infected by poliovirus if susceptible may get permanent disability.
What are manifestations of Polio Disease?
Abortive poliomyelitis: 5 percent children of those got infected, show non specific symptoms. This is called as abortive poliomyelitis. In this type of poliomyelitis patient have non specific flu like symptoms presenting as fever, malaise, fever, malaise, anorexia, sore throat, headache, abdominal and muscles pain may occur. The course of duration is short lasting for 2-3 days and recovery is complete with no neurological findings.
Nonparalytic poliomyelitis: In this type of poliomyelitis more intense headache and nausea and vomiting is present. There is increased spasticity of back muscles and posterior muscles and also the neck rigidity.
Paralytic poliomyelitis: This is type of poliomyelitis occurs in 3 forms spinal poliomyelitis, bulbar poliomyelitis and polioencephalitis.
- Spinal poliomyelitis: In this form of poliomyelitis initial presentation is that of abortive poliomyelitis. Patient recovers and is well for 2-5 days. Then appears to be suffering from previous symptoms exacerbation. It is accompanies by sensory and muscular phenomenon. Hyperasthesia and fasciculation occurs initially. There is intense muscle pain. Paresis of the muscles is spotty and few or single muscles are initially involved showing the paresis. Then the disease may progress to involve one les asymmetrically followed by one arm generally. This disease is dramatic with some cases showing full recovery to some cases progressing to total paralysis and permanent disability with no signs of recovery.
- Bulbar poliomyelitis: This involves only cranial nerves and medullary regions without involving entire spinal cord. In this form of poliomyelitis the signs of cranial nerve paresis are seen. Nasal twang, inability to swallow, accumulation of secretions in mouth and pharynx giving picture of respiratory difficulty, inability to cough, nasal regurgitation of saliva and vomiting, deviation of the palate, uvula and tongue, involvement of vital centres of medulla leading to irregular respiration and heart rhythm, fluctuation in blood pressure, paralysis of vocal cord leading to aphonia and finally asphyxia,
- Polioencephalitis is a rare form in which higher centers in the brain and cortex is involved. The signs are suggestive of encephalitis. Seizure, coma, altered sensorium, drowsiness and irritability these are some signs of encephalitis.
Prevention of poliomyelitis:
Polio vaccine is the most effective and cheaper way of preventing the disease and its complications. Since the worldwide acceptance of the polio vaccine in universal immunization schedule and implementation of the same in national immunization schedules of many countries the disease is extinct from many countries and occurs rarely in only few countries like Pakistan.
Active/live polio vaccine: Live polio vaccine currently used is bivalent vaccine. It contains only polio virus type 1 and type 3. It contains live virus which upon giving this vaccine infects the child and child develops immunity against it. Although these are live virus in vaccine it does not have capacity to cause disease in the healthy recipient. This vaccine is very effective only drawback is cold chain is to be maintained very strictly. As temperatures are higher in countries like India multiple doses are needed to be given to maintain the protection in the general population. It vaccine cannot be given to those who have HIV infection with stage 3 and 4 AIDS disease. It cannot be given to pregnant and severely immunocompromised patients. Currently zero dose that is birth dose and dose at 5 year are to be given as oral polio vaccine but all the other doses that is at 6, 10, 14 weeks and at 18 months are to be given with inactivated polio vaccine.
Inactive/killed polio vaccine (IPV): In this vaccine Poliovirus type 1, 2, and 3 are present. They are inactivated that is killed. When injected to the child, the immunity of the child detects the virus antigen and it develops antibodies against the real virus. As this vaccine is killed it can be given to those with AIDS and those with severely immunocompromised status. It is safe in pregnancy. Currently this vaccine is given at 6 weeks and 10 weeks and 14 weeks and 18 months of age. The development of immunity to this vaccine is excellent almost reaching to 100 percent after 4 doses. After eradication of the poliovirus this inactivated polio vaccine (IPV) will be used for some years as we need to maintain the immunity of the population so the the disease does not return.
Currently IPV- inactivated polio vaccine is available as combination vaccine namely Hexavalent vaccine (Easysix and Hexaxim and infanrix hexa) or pantaxim. These vaccines contain Hepatitis B, Haemophilus influenzae type b (HiB), diphtheria, tetanus, pertussis components along with IPV.