The Claim:
An anti-vaccine activist is once again claiming that vaccines for polio and measles do not provide immunity. He supports this claim by saying measles deaths dropped before the vaccine came out and polio rates dropped because the CDC redefined polio.
The Facts:
Measles is one of the most transmissible infections in humans. One infected person can infect 12-18 others in a group of susceptible people. Prior to vaccines, it was expected that nearly everybody would get measles at some point in their life, usually during childhood. If the measles vaccine conferred no immunity, as the tweeter suggests, measles would still be circulating freely. Instead, almost no one gets measles anymore.
Yes, measles mortality did decline before the introduction of the measles vaccine due to better medical treatments. Measles cases, however, did not decline until after vaccination began.
This common trope relies on confusing death (mortality) and illness (morbidity). Medical advances slowed down the death rate from measles, but vaccines stopped it.
As for polio, it has not been redefined. The elimination of polio, especially in the United States, was primarily due to the widespread use of effective vaccines. The development of the polio vaccine in the 1950s was a significant breakthrough in medical science. These vaccines were highly effective in preventing polio, and gave mid-century children their childhoods back and parents peace of mind.
The definition of polio, an illness caused by a specific virus called poliovirus, which can be isolated and tested for, that affects the nervous system, has remained consistent over the years. Furthermore, polio is identifiable by more than just the words used to describe it. The virus has been visible through an electron microscope since the 1950s. Polio surveillance of wastewater worldwide alerts global health experts where the disease may be spreading. None of these tests for polio rely on a definition, and that’s why we can be sure that polio didn’t go away because the CDC changed the words to describe it.
Global Health scientists have been involved in a global polio eradication initiative, which has been successful in drastically reducing polio cases worldwide through mass immunization campaigns and surveillance.
Disclaimer: Science is always evolving and our understanding of these topics may have evolved too since this was originally posted. Be sure to check out our most recent posts and browse the latest Just the Facts Topics for the latest.
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