Background:

The availability of two effective vaccines against poliomyelitis for the past five decades has ensured a remarkable decline in the global burden of diseases. They were developed in the USA during 1950, first the inactivated polio vaccine (IPV) by Jona Salk and later the live oral polio vaccine (OPV) by Albert Sabin. The global polio eradication initiative was launched in 1988 using oral polio vaccine as the eradication tool and employing a foot pronged strategy comprising high routine immunization coverage, supplementary nutrition, pulse immunization, AFP surveillance and Mop-up immunization.

Age Group: Affects child under 5 years

Transmission:

• Through person to person contact
• Virus Enters through the mouth
• Virus Shed through the faeces
• Can be spread when food or drink is contaminated by faeces

Oral Polio Vaccine (OPV):

• A trivalent vaccine consisting of attenuated poliovirus types 1, 2, 3 grown in monkey kidney cell culture stabilized with magnesium chloride.
• Monovalent OPV, that means containing either type 1 or type 3 viruses have been introduced in India since 2005.
• Bivalent OPV containing type 1 and type 3 viruses have been introduced since 2010 for pulse immunization.
• The dose is 2 drops orally.

Inactivated Polio Vaccine (IPV):

• It is formaldehyde killed poliovirus grown in human diploid cells/monkey kidney cells.
• Currently used IPV vaccines are enhanced potency IPV which contains 40, 8 and 32 D antigen units of type 1,2, 3 respectively.
• The vaccine should be stored at 2- 8 degree and the dose is 0.5ml intramuscularly.
• Highly immunogenic, seroconversion rates are 90-100% after two doses.
• It contains trace amounts of streptomycin, neomycin and polymyxin B, and antimicrobials.

OPV vs IPV:

OPV
Good IgA response (Mucosal immunity) 
Lower humoral response

IPV
Low IgA response
Strong humoral response(IgG)

What is Mucosal Immunity?

It refers to the resistance to mucosal infection by wild poliovirus due to prior infection with WPV. Mucosal immunity decreases the replication and excretion of the virus and thus provides a potential barrier to its transmission.

What is Humoral Immunity?

It refers to IgG antibodies which have an inhibitory influence on local infection.

Herd effect with Polio Vaccines:

Herd effect means the phenomenon of immunized individuals affecting the epidemiology of infection in the unimmunized segment of the population.

• In OPV effect is mainly due to its excellent gut immunity.
• In IPV due to induction of high levels of antibodies.

Recommendation for combined use of OPV and IPV:

• Excellent immunogenicity, efficacy, and safety.
• The risk of VAPP is extremely low.
• Better mucosal and humoral immunity together.

Doses and Schedule:

• OPV at birth.
• OPV and IPV at 6, 10, I4 weeks.
• OPV at the sixth and ninth month.
• OPV and IPV at 15-18 months.
• OPV at 5 years.

Catch-up Vaccination:

IPV may be preferred as catch-up vaccination for children less than 5 years of age who have completed primary immunization with OPV. IPV can be given two doses at 2 months interval.

Immunodeficient Children and their close contacts:

• IPV is preferable in patients with B cell immunodeficiency.
• OPV should be avoided.
  Vaccinate your baby with polio vaccines and make your baby grow stronger with no disabilities.