Polio virus bits in vaccine rarely join forces with other viruses, become infectious
[Note: some of the links in this piece are to New England Journal of Medicine papers. NEJM does not make its content freely available, so unfortunately, unless you have academic or other access, you’d have to pay per view to read the information. I fervently support a world in which scientific data and information are freely available, but…money is money.]
Worldwide, billions of polio vaccine doses have been administered, stopping a disease scourge that before the vaccine killed people–mostly children–by the thousands in a horrible, suffocating death (see “A brief history of polio and its effects,” below). The polio vaccination campaign has been enormously successful, coming close to the edge of eradicating wild-type polio.
But, as with any huge success, there have been clear negatives. In a few countries–15, to be exact–there have been 14 outbreaks of polio that researchers have traced to the vaccines themselves. The total number of such cases as of 2009 was 383. The viral pieces in the vaccine–designed to attract an immune response without causing disease–occasionally recombine with other viruses to form an active version of the pathogen. Some kinds of viruses–flu viruses come to mind–can be notoriously tricky and agile that way.
Existing vaccine can prevent vaccine-related polio
Odd as it sounds, the existing vaccines can help prevent the spread of this vaccine-related form of polio. The recombined vaccine-related version tends to break out in populations that are underimmunized against the wild virus, as happened in Nigeria. Nigeria suspended its polio vaccination program in 2003 because rumors began to circulate that the vaccine was an anti-Muslim tactic intended to cause infertility. In 2009, the country experienced an outbreak of vaccine-derived virus, with at least 278 children affected. Experts have found that the existing vaccine can act against either the wild virus or the vaccine-derived form, both of which have equally severe effects. In other words, vaccinated children won’t get either.
Goal is eradication of virus and need for vaccine
Having come so close to total eradication before wild-type-associated cases plateaued between 1000 and 2000 annually in the 21st century, global health officials hold out the hope for two primary goals. They hope to eradicate wild-type polio transmission through a complete vaccination program, which, in turn, will keep vaccine-derived forms from spreading. Once that goal is achieved, they will have reached the final target: no more need for a polio vaccine.
As Dr. Bruce Aylward, Director of the Global Polio Eradication Initiative at WHO, noted: “These new findings suggest that if (vaccine-derived polio viruses) are allowed to circulate for a long enough time, eventually they can regain a similar capacity to spread and paralyse as wild polioviruses. This means that they should be subject to the same outbreak response measures as wild polioviruses. These results also underscore the need to eventually stop all (oral polio vaccine) use in routine immunization programmes after wild polioviruses have been eradicated, to ensure that all children are protected from all possible risks of polio in future.”
If that sounds nutty, it’s been done. Until the early 1970s, the smallpox vaccination was considered a routine vaccination. But smallpox was eradicated, and most people born after the early ’70s have never had to have the vaccine.
A brief history of polio and its effects
I bring you the following history of polio, paraphrased from information I received from a physician friend of mine who works in critical care:
The original polio virus outbreaks occurred before the modern intensive care unit had been invented and before mechanical ventilators were widely available. In 1947-1948, the polio epidemic raged through Europe and the United States, with many thousands of patients dying a horrible death due to respiratory paralysis. Slow asphyxiation is one of the worst ways to die, which is precisely why they simulate suffocation in torture methods such as water boarding. The sensation is unendurable.
In the early twentieth-century polio epidemics, they put breathing tubes down the throats of patients who were asphyxiating due to the respiratory paralysis caused by the polio virus. Because ventilators were unavailable, armies of medical students provided the mechanical respiratory assist to the patients by hand-squeezing a bag which was connected to the breathing tube, over and over and over, 16 times a minute, 24 hours each day, which drove air in and out of the patients’ lungs. Eventually the iron lung was developed and became widely implemented to manage polio outbreaks. The iron lung subsequently gave way to the modern ventilator, which is another story.