the oral polio vaccine, Racaniello and Schaffner said.
The oral vaccine was the first developed and the easiest to administer, so it is still used as part of the World Health Organization‘s polio eradication efforts around the globe, according to experts. But, Racaniello says, it’s an infectious vaccine, meaning it contains a weakened version of the virus itself.
“It reproduces in your intestines, and you shed it — that’s the virus in the sewage,” he notes. “That virus gets around very easily, and it can cause polio even though it’s a vaccine virus. After it passes through the human gut, it can reacquire the ability to cause polio.”
The United States stopped using the oral vaccine in 2000, after the U.S. Preventive Services Task Force decided that the risk of even a few incidental cases of polio was too great, Schaffner shares.
“Each year we had about 4 million births and we had somewhere between six and 10 cases of vaccine-associated poliomyelitis,” he says. “We were giving a very small number of children and adults paralysis by using the oral vaccine.”
The U.S. now exclusively uses a four-dose inactivated polio vaccine.
“The virus is killed. There’s no possibility it can multiply. It cannot mutate. It cannot cause paralysis,” Schaffner shares. “But as an inactivated viral vaccine, it has to be given by needle and syringe, which is more cumbersome and considerably more expensive and, of course, added to the number of inoculations little children were getting, which didn’t make moms too happy.”
Schaffner says it’s “notable” that vaccine-related poliovirus is circulating in the United States.
“We wouldn’t have expected it to be widely disseminated, so we’re just finding there’s even more intercontinental transmission of these oral polio vaccine viruses than we thought,” Schaffner notes.
“If you had asked me before this case, I would have said that unless somebody has just gone abroad or had a visitor from abroad, you wouldn’t find it here because we’re not using [the oral vaccine] in the United States,” Schaffner adds. “But we may be a smaller global community even than I thought.”
How to protect yourself
The only true protection is vaccination, and Racaniello hopes that wastewater surveillance data will help persuade the vaccine-hesitant to go ahead and get their jabs.
“Maybe they thought there was no poliovirus in the U.S., right? And so they say I don’t need to get vaccinated,” Racaniello says. “And so now we can show them that there is. In fact, I think we should do more surveillance of wastewater and show people, look, it’s in every major metropolitan city. You better get vaccinated.”
Healthcare officials recommend four polio shots in childhood:
- First shot at 2 months old.
- Second shot at 4 months old.
- Third shot between 6 and 18 months old.
- Booster shot between 4 and 6 years old.
If you’ve never been vaccinated for polio and it’s recommended you get vaccinated as an adult, you’ll get three shots:
- Two doses one to two months apart.
- A third dose six to 12 months after the second.