Who is at risk?: According to the CDC’s Laboratory Surveillance for Wild and Vaccine-Derived Polioviruses, January 2003–June 2004, no one in the Americas are at risk for wild-polio. (There have been no cases of wild poliomyelitis in the U.S. since 1999). However, there were 54 cases of vaccine-derived polio in the Americas between January 2003 and June 2004.
Inactivated polio vaccine (IPV) needs to be injected and works by producing protective antibodies in the blood (serum immunity) – thus preventing the spread of poliovirus to the central nervous system. However, it induces only very low levels of immunity to polivirus locally, inside the gut. As a result, it provides individual protection against polio paralysis but, unlike OPV, cannot prevent the spread of wild polio virus.
Manufacturer’s Inserts and Efficacy statements:
IPOL-efficacy not listed in package insert-states that:
Poliovirus Vaccine Inactivated induces the production of neutralizing antibodies against each type of virus which are related to protective efficacy.
Approval in the US was based upon demonstration of immunogenicity and safety in US children.
(Immunogenicity is simply the ability of your body to recognize a foreign substance and elicit an immune response.)
Manufacturer’s seroconversion rates:
After two doses of vaccine given during the first year of life, seroprevalence rates for detectable serum neutralizing antibody (neutralizing titer ³1:4) were 88% to 100% (Type 1); 84% to 100% (Type 2) and 94% to 100% (Type 3) of infants, depending on studies.
* Seroconversion means antibodies exist. Not that they function.
An interesting fact: IPOL actually uses the 1950’s Salk data from the pulled vaccine to demonstrate effectiveness.
As is quoted in the IPOL Package Insert references:
8. Salk J, et al. Antigen content of inactivated poliovirus vaccine for use in a one- or two-dose regimen. Ann Clin Res 14: 204-212, 1982
9. Salk J, et al. Killed poliovirus antigen titration in humans. Develop Biol Standard 41: 119-132, 1978
10. Salk J, et al. Theoretical and practical considerations in the application of killed poliovirus vaccine for the control of paralytic
poliomyelitis. Develop Biol Standard 47: 181-198, 1981
11. Unpublished data available from Sanofi Pasteur SA
12. Unpublished data available from Sanofi Pasteur Inc.
eIPV (or IPOL) hasn’t been scientifically demonstrated in a blinded, controlled trial. Effectiveness is unknown.
From IPOL package insert:
Approximately 90% to 95% of poliovirus infections are asymptomatic. Nonspecific illness with low-grade fever and sore throat (minor illness) occurs in 4% to 8% of infections.
From The Present Status of Polio Vaccines transcript published in the Illinois Medical Journal:
We must also distinguish between polio infection and the clinical disease. Tuberculosis, where we have the tuberculin reactor which signifies infection as contrasted to the reportable clinical disease, is the prototype. For every one case of known paralytic polio we have about a thousand cases of subclinical polio infections. The latter accounts for the high degree of natural immunity in adults. Crucial to the understanding of the contemporary vaccine problem is that you can get infection of the gut with or without disease.
The theory of the killed vaccine is that circulating antibodies in sufficient amounts will neutralize poliovirus before it reaches the central nervous system. One of the major disappointments of the killed vaccine is that circulating antibodies alone do not protect against alimentary infection. Only when local immunity follows an alimentary infection are we capable of achieving a more consistent immunity against the disease.