Polio (OPV, IPV)

Polio is a viral disease which, in its early phases, produces only mild or subtle symptoms. It may actually stop there, or it may progress to a second stage where it can enter the brain and spinal cord causing pain, permanent paralysis, and sometimes death. There is no effective treatment for Polio. Prior to the development of vaccines, Polio paralyzed between 13,000 and 20,000 Americans every year. It was virtually impossible to grow up in the WWII era and not know of at least one friend who was killed or left in a wheelchair by Polio!

Today Polio has been almost eradicated – there has not been a “wild” case reported in the Western Hemisphere for almost two decades, and rates are low and falling in Africa/Asia as well. There are two effective vaccines against it – Oral Polio Vaccine (OPV) and Inactivated/Injected Polio Vaccine (IPV).

OPV is a live-virus vaccine in which the Polio germ has been altered so that it is unable to paralyze humans. When we give OPV it multiplies in the recipient and is “contagious” just like any other germ. It comes out in urine, stool and saliva and spreads to family, friends, and neighbors – in effect giving them all silent “booster doses” of the vaccine! This “many vaccines for the price of one” effect partly explains why OPV works better than IPV at a population-wide level! The other reason it is superior relates to it’s similarity to the “natural” disease. This induces antibodies not just in the blood but also in saliva and other mucous membranes, giving a “first line defense” not seen with the alternative IPV. Rarely, however, the OPV virus mysteriously and spontaneously changes (“mutates”) back to a paralytic form. When this happens it can result in what we call “Vaccine-Associated Paralytic Polio” (VAPP) – a disease which is indistinguishable except by a blood test from regular or “wild type” Polio. During the 1990’s VAPP happened 5-10 times per year in the United States, and for many years represented ALL of the cases of clinical Polio seen in the Western Hemisphere! OPV had no side effects, VAPP was it’s only major risk.

There is no risk of VAPP from IPV. The only common side effect is a bit of redness and soreness at the injection site, and the only serious risk is that of an allergic reaction (very rare).

For more information, please visit Centers for Disease Control and Prevention (CDC) website at:

Polio (OPV):: http://www.immunize.org/vis/opv-00.pdf