Among the routine vaccines used in every child in the U.S. today is polio vaccine. Many parents remember getting the oral polio vaccine, but this has not been used in almost 20 years. Now, all polio vaccine in the U.S. is given as IPV (injected polio vaccine), either an intramuscular or subcutaneous injection over 4 doses, from infancy through preschool.
Polio is a viral infection which attacks the brain and spinal cord, causing a rapidly spreading paralysis. In some cases, affected patients have a mild course with paralysis or only weakness of the legs and arms and recover, sometimes completely. In other cases, limb weakness remains as a lifelong disability. In the worst cases, the paralysis also affects the respiratory muscles and can cause death.
Oral (live) polio vaccine was phased out in the U.S. and much of the developed world by the year 2000 due to rare but possible reversion (mutation) of the vaccine virus into a version that can cause actual polio (called, among other names, vaccine-derived poliovirus, or VDPV). However, since the injected (killed) form is much more expensive and requires needles and syringes, much of the developing world still uses oral polio vaccine despite the tiny risk of reversion. The WHO and the Gates Foundation are working on a complicated plan to move the entire world to a system of IPV-only use. Given the regions involved and the cost, this is a very complicated project, but unfortunately the biggest obstacle is still ongoing war in all of the countries still affected by polio.
Since the U.S. has not seen polio infection in over 35 years, many parents ask about why we still need the vaccine here. This is because polio is very contagious, and although nearly eliminated worldwide, it is still endemic in Afghanistan, Nigeria and Pakistan. Syria has also seen several recent cases of a polio strain imported from Pakistan. Allowing vaccination levels to drop below what is needed for effective herd immunity would leave a region’s population vulnerable to cases spread by travel by tourists, diplomatic families and refugees. Luckily, the polio vaccine is most commonly given combined with other vaccines as a single injection.
Given the ongoing civil (and uncivil) wars in many of these regions, there is little chance for the WHO’s plans (called the The Polio Eradication & Endgame Strategic Plan 2013-2018) for eradication of polio this year be realized.
U.S. vaccination schedule (note – oral polio vaccine is not used in the U.S.):
- IPV at 2, 4, and 6 months (usually combined with other vaccines)
- IPV at 4-6 years old (usually combined with other vaccines)