In November, the CDC declared it would expand wastewater testing for the detection of polio in America. The polio virus has unfortunately returned to American shores, decades after we had thought it eradicated. Jose Romero is CDC NCIRD (National Center for Immunization and Respiratory Diseases) director, and had this to say:

“When will we know that we’re out of the woods? When we get our vaccine rates at the national level — 93 or 94 percent — to have herd immunity in the community,” Romero said, referring to when enough individuals have been vaccinated so their collective immunity prevents the virus from circulating in that population

Via Washington Post

A fine sentiment, and a call for greater vaccination. Which would be all well and good if Romero’s statement on vaccines causing herd immunity wasn’t total disinformation. Before I get to why this statement is false, I first want to discuss why I’m writing this and why this is important. American public health has taken a blow over the past several years and in many ways this can be traced back to people’s growing distrust of public health officials. The causes for this distrust are varied, but because of the mistrust it is imperative that public health officials deliver accurate and relevant information to the public to help regain the public’s trust. I find it hard to believe that Jose Romero, who is an MD and the CDC NCIRD director, does not know or realize that his statement is false. I find it more likely that he is telling a public health white lie of the type that has become all too common, saying something false in order to encourage behavior he’d like to see. In this case, he wants to encourage more vaccine uptake, so instead of saying the truth (that the American polio vaccine only protects the recipient from paralytic polio and does not promote herd immunity or reduce community spread), he is saying something that he thinks will get more unvaccinated people to want to get the vaccine. The problem is that what he’s saying is wrong, actual scientists can tell us he’s wrong, and agenda-driven actors can then use his wrongness to discredit whatever else he is trying to say.

It you want two MDs to explain why Jose is wrong, This Week in Virology has you covered, but I will explain as best I can.

The polio virus is known to cause paralysis, but this is a secondary effect, the virus primarily infects the intestines. About 90% of people infected with polio will develop either no symptoms, or mild symptoms (fatigue, fever, diarrhea etc) but not paralysis. In 1% of polio infection the virus then spreads throughout the central nervous system, causing damage to nerve cells which leads to muscle paralysis. There are two main classes of vaccine that can protect against polio, the oral polio vaccine (OPM) and the inactivated poliovirus vaccine (IPV). It’s important to note that America only uses the IPV. The OPM contains a weakened form of the virus which is capable of replicating, and because it can replicate this weakened virus can then be passed on to others, infecting them as well and potentially causing paralysis in them. However this vaccine allows the entire immune system to come in contact with the virus and build defenses against it. The IPV does not contain a virus, only pieces of the virus are injected into the patient. Because of this, the virus cannot replicate and thus cannot be spread to others, but it also does not immunize as strongly as the OPM. So what if someone who received the IPV comes into contact with poliovirus? They are not so strongly immunized, so the virus can still replicate inside them and be excreted in the stool. But they are immunized enough to be protected against the major polio symptoms especially paralysis.

So to recap: the OPM is effective at preventing people from acquiring and spreading polio, but because it contains an actual virus, there are major downsides that must be considered. The IPV is not effective at preventing people from acquiring and spreading polio, but it prevents all the worst symptoms and has less downsides to its use. America only uses the IPV, so increasing our vaccination uptake will not prevent the acquiring or spreading of poliovirus and will not lead to herd immunity. The vaccine used in America only prevents people from getting paralyzed if they get infected with polio.

I think Jose Romero (or his staff) must know this, but I think they (like too many public health officials) are trying to influence behavior by shading the truth. This is a pattern of behavior that Josh Barro has also chronicled, dishonest framing has been used to obscure the truth for ostensibly noble ends. But lying doesn’t help, when people realize you’ve lied they become far less likely to trust you later. And for our nation’s public health community to continue this further decline in trust could prove disastrous.