According to a very informative article by the Children’s Hospital of Philadelphia, there are two types of Polio Vaccines. Below we look at the specifics of these two vaccines.
What types of Polio Vaccines are available?
There are two types of Polio Vaccines the inactivated polio vaccine (IPV) and the oral polio vaccine (OPV). The IPV was made first in 1955 and is administered by a shot. The OPV which was made in 1961 is more convenient and is given by liquid form. These vaccines have been incredibly effective and have eradicated Polio in the US since 1979 and the Western Hemisphere since 1991. IPV is the only polio vaccine that is used in the US.
How Were the Vaccines Made Initially?
Oral Polio Vaccine
The OPV was created from weakening three strains of the poliovirus that caused the disease by growing these strains in monkey kidney cells. Because this was growing the kidney cells the virus was able to be weakened where if ingested it would create an immune response that didn’t cause the disease. The OPV allows the body to have a first defense against the disease because the induced antibodies are in the intestines. But OPV rarely went back to the natural form which eventually caused paralysis.
Inactivated Polio Vaccine
The IPV, unlike the OPV, could not reproduce by itself which means that it does not have the capability to revert back to its natural form. In order to make IPV, the poliovirus is purified and killed with formaldehyde. Also unlike the oral vaccine, the IPV does not create antibodies in the intestines but rather in the bloodstream. This prevents the virus from traveling through the blood into the brain or spinal cord which then disables paralysis.
Why does the US use only the Inactivated Polio Vaccine?
We only use the Inactivated Polio Vaccine instead of the Oral Polio Vaccine because the IPV cannot replicate which means it will never revert back to the natural form and cause paralysis. Now every infant in the US is required to have four doses of the shot. On the other hand countries outside of the US still use the oral version because it is more affordable and easier to give which allows more people to receive the vaccine.