Does the polio vaccine cause polio?

imgres-2One claim that I’ve heard a lot from vaccine opponents is that the polio vaccine is actually causing polio epidemics instead of preventing them. Scary, right? On websites like “GreenMedInfo” you see headlines like Polio vaccines now the #1 cause of polio paralysis. And Joseph Mercola maintains that because of problems like this, “the polio vaccine is not the ultimate solution to prevent” polio.

Is any of this true? As it turns out, there IS a grain of truth to this claim. But the truth is way more complicated than vaccine skeptics seem to understand, and, as it happens, the solution is more vaccination, not less.

Here’s the deal. There are two types of polio vaccine, one that involves the injection of dead virus and another that involves oral drops filled with live (but non-disease causing) virus. Here in the U.S., we use the first type of vaccine. But there are many benefits associated with the second type of vaccine: it’s easier to administer (drops vs shots), it provides stronger protection, and here’s the biggie: because it can spread after being administered, it effectively inoculates other people in the community. This is called passive immunization, and it’s definitely a good thing! It means the protection of the vaccine extends beyond just the people who get vaccinated. The virus can remain in a child’s feces for up to six weeks, during which time she has the potential to inoculate the people around her.

There is a dark side to this passive immunization, though. Give the vaccine-derived virus enough time to spread, and it can begin to mutate. Tick tick tick. Enough mutations, and it may regain its ability to paralyze. When does this happen? When the proportion of vaccinated kids is low. Surrounded by plenty of susceptible kids, the likelihood that a vaccine-derived virus can circulate for long enough to gain these mutations goes way up.

Unfortunately, this situation sometimes occurs. There have been a number of vaccine-derived outbreaks of polio. In total, scientists think that, since the year 2000, there have been 20 outbreaks of vaccine-derived polio in 20 countries, resulting in 655 vaccine-derived polio cases. The biggest outbreak, involving hundreds of kids, happened in Nigeria. This isn’t surprising, because vaccination stopped in some regions of the country for over a year in the early 2000s.

The counterintuitive solution to fighting vaccine-derived outbreaks is to increase vaccination rates. That way, children are inoculated with the harmless version of the virus and can’t be infected with any “bad” versions floating around. Vaccine-derived strains are nipped in the bud before they have time to accumulate dangerous mutations.

One thing to ask people critical of the polio vaccine because of vaccine-derived outbreaks is what they recommend as a substitute. Joseph Mercola’s big idea is to cut down on sugar, apparently. Sadly, sugar consumption isn’t a big problem in most of the places where polio is still a problem. So I think we can rule that solution out. Sayer Ji, founder of GreenMedInfo, recommends improved sanitation. While improved sanitation certainly cuts down on opportunities for infection (polio is spread through the fecal/oral route), it can paradoxically create more opportunities for paralysis. Why? The older you are when you become infected with polio (and the age of infection goes up when opportunities for infection go down), the greater the odds of paralysis. So I think we can rule that solution out too (although improved sanitation has many other benefits, and it is definitely a worthwhile goal).

So while vaccine-derived polio outbreaks are a real thing, they are not a reason to abandon the polio eradication campaign, which has reduced the number of new polio cases by 99% since it began in the late 1980s.