Is the Polio Vaccine Still Required in U.S. and Why Was OPV Stopped?

Polio returned to the headlines this week after the first case of the disease in the United States for nearly a decade was detected in New York. While vaccines for polio have existed for years, there is no federal law requiring mandating the vaccine.

Polio is a disease caused by the highly infectious poliovirus that can cause paralysis and death in severe cases.

Widespread use of polio vaccines, which began in the 1950s, helped to eradicate polio across most of the world, including the United States, although sporadic cases do still occur in countries even where the disease has technically been wiped out. The virus is endemic to some parts of the world—polio cases are still detected in Afghanistan and Pakistan, for example.

Polio vaccines are highly effective at protecting against the disease. In the United States, the first polio vaccine became available in 1955. There are two types of polio vaccine: the oral poliovirus vaccine (OPV) and the inactivated poliovirus vaccine (IPV), although only the latter is still used in the United States.

Is the polio vaccine still required in the U.S.?

The IPV vaccine, which is the only one used in the U.S., provides around 90 percent immunity against all three types of poliovirus after two doses, and at least 99 percent immunity after three doses, according to the Centers for Disease Control and Prevention (CDC).

While there is no federal law that requires people to get this vaccine, which is given by a shot in the arm or leg depending on the person's age, all 50 states and the District of Columbia have state laws requiring children who are entering childcare or public schools to have this vaccination.

The CDC recommends that all children get four doses of IPV: one at two months old, one at four months old, one at six through 18 months old, and a final shot at four through six years old.

Health officials say the best way to keep the United States free of polio is to maintain high levels of immunity through vaccination efforts.

In most cases, adults today would likely have been vaccinated against polio as children and, thus, do not need to get the polio vaccine. However, the CDC recommends that certain groups who have never been vaccinated against the disease should consider getting three doses of IPV.

These groups include people who are traveling to a country with a higher risk of contracting polio, people who work in labs who may be exposed to samples containing polioviruses and health care workers treating potential polio patients.

Why was the use of OPV stopped in the U.S.?

In the U.S., the use of the OPV vaccine was stopped in 2000, although it is still used in many parts of the world.

The OPV vaccine contains live polio virus, albeit in a weakened form, and is highly effective at protecting against the disease. In fact, OPV tends to be more effective than IPV at mitigating the spread of the disease between people.

However, in extremely rare cases, the weakened virus in the OPV vaccine has mutated into a form capable of causing disease. As a result, U.S. health authorities switched to only using the IPV vaccine in 2000, which contains an inactivated form of the poliovirus and, thus, cannot cause disease.