Health Officials Call for the Virtual Elimination of Live Polio Vaccine

From the WebMD Archives

Dec. 8, 1999 (Atlanta) -- Beginning next year, the use of oral drops as a childhood vaccination against polio should be phased out in the United States in favor of the injectable vaccine, according to recommendations being made by the American Academy of Pediatrics and the CDC. Both organizations say that pediatricians should stop using the oral vaccine within the first six months of 2000.

The injectable vaccine will add another pair of shots to a child's vaccination schedule, but studies have shown that it is safer than the oral vaccine, which actually contains a weakened but live form of polio. That makes it more potent than the injectable vaccine, but that potency comes with a greater risk.

The phasing out of the oral polio vaccine began in 1997 when the American Academy of Pediatrics and the CDC recommended sequencing the injectable and oral polio vaccines. This change reflected the concern about vaccine-associated polio. Since 1979, there have been no incidents of polio in the United States except a handful of cases each year associated with receiving the oral vaccine.

"We're going to a vaccine that will eliminate the only major adverse event associated with a polio vaccine, and that is the actual risk of polio and paralysis," Edgar Marcuse, MD, a professor of pediatrics at the University of Washington, tells WebMD.

Both the oral and injectable vaccines work by introducing different strengths of the virus into the body, says Marcuse. The body reacts by producing antibodies and blood cells via the immune system. The immune response guards against any future contracting of the disease, similar to the workings of numerous vaccines. The injectable vaccine is a dead version of the virus, but one the body still recognizes as polio.

The new recommendations, which appear in the December issue of the journal Pediatrics, call for an all-injectable schedule for the routine immunization of infants and children against polio. The timing of the vaccinations would remain the same.

There are four polio vaccines recommended throughout childhood. Currently, the first two doses are injectable and given at 2 and 4 months of age. These are then followed by an oral dose given between 6 and 18 months of age and then again between the ages of 4 and 6 years.

"After the sequential schedule began, it cut down the use of the oral vaccine by half, and that cut the number of cases [of polio] by about half, so that rationale [for wholesale change] has been speaking for itself," says Marcuse.

According to the CDC, there were 5 confirmed cases of vaccine-associated polio in 1997 and 1 case in 1998. "There is hope that within the next decade we can eliminate polio vaccines altogether as the disease nears eradication," says Marcuse.

Even though the oral polio vaccine is a stronger guard against polio, health officials no longer believe the need to fight the disease is worth the risk as the prevalence of the polio has virtually disappeared in the U.S.

"It's hard to justify using a vaccine that could, although rarely, lead to a risk of polio as the risk of importation and epidemic has fallen," says CDC epidemiologist Rebecca Prevots, PhD.

"Given a painful shot with no risk or a painless drop with small risk, most parents are already choosing the shot," pediatrician Marc Tanenbaum, MD, tells WebMD. "I tell parents there is a four in 10 million chance of contracting the disease with the first oral dose but that's usually enough." Tanenbaum is with Pediatrics and Adolescent Medicine, a group practice in Atlanta.

Tanenbaum says that he will keep his current stock of oral vaccine in cases of parent preference. "I'm comfortable with the risk of the oral vaccine and none of us like shots, but I know it's in the child's best interest."

The AAP recommendations support keeping the oral vaccine in stock for cases in which the stronger vaccine will be necessary, such as when unvaccinated children are traveling within four weeks to countries where the disease still exists.

Marcuse says that although the injectable vaccine is weaker, it is more than adequate for domestic use. "The newer injectables are enhanced inactivated polio vaccines, and we have every reason to believe will provide durable immunity that will almost certainly be lifelong."