News reports about polio worry many parents. Here’s what to know and do.
If you don’t know much about polio, that’s understandable. Thanks to vaccination, there have been no cases of wild polio originating in the United States since 1979.
Unfortunately, that doesn’t mean there isn’t polio in the United States. Travelers from other countries can bring it – either wild poliovirus or “vaccine-derived” virus. Recently, we have heard of polio cases, mostly of vaccine origin, and mostly from other countries, but sewage data shows that poliovirus is spreading in some areas. Here’s what parents need to know.
What is vaccine-derived poliovirus?
The polio vaccine helps the body make the antibodies it needs to fight polio. The oral polio vaccine used in many countries contains a weakened version of the poliovirus. Since 2000, the United States has only used an inactivated vaccine, based on a killed version of the virus and administered by injection.
The vaccine-derived virus comes from the oral polio vaccine. Although the oral vaccine is effective and generally safe, the weakened virus can cause illness in people with weakened immune systems. The disease can spread when there are many unvaccinated people.
Widespread vaccination boosts herd immunity that protects against poliomyelitis
If enough people are vaccinated, the occasional traveler with wild or vaccine-derived poliovirus is not a problem. Herd immunity is the term used to describe how vaccination protects people: if enough people are protected by vaccination, it is difficult for the disease to spread, which protects people who are not vaccinated.
The percentage of people who need to be vaccinated to stop the spread varies from infection to infection; for poliomyelitis, the number is around 80% to 85%. While most children in the United States are vaccinated against polio, vaccine hesitancy remains a problem, especially when unvaccinated children live in groups where infections can spread. These days, you can’t always rely on herd immunity to protect unvaccinated children.
What should parents know about poliomyelitis?
It can be dangerous. Most people who get the virus have no or mild flu-like symptoms, which can allow it to spread quietly. In some cases, poliomyelitis can affect the brain and spinal cord. In about one in 200 people who catch poliomyelitis, it can lead to paralysis or even death. In the late 1940s, polio epidemics disabled approximately 35,000 people each year.
Immunization works. With the development of inactivated and oral polio vaccines in the 1950s and 1960s, the number of cases of polio paralysis in the United States dropped rapidly – from 15,000 in the 1950s to 10 in the 1970s.
- The poliomyelitis vaccine is remarkably effective. Two doses of the inactivated vaccine are 90% effective in preventing poliomyelitis; with a third dose, this protection increases to 99% to 100%. The currently recommended schedule is one dose of inactivated vaccine at 2, 4 and 6 months of age, with a booster dose at 4 to 6 years of age.
- The vaccine is safe. Some people feel lightheaded briefly after receiving it, and there may be redness or pain at the injection site. Any medical treatment can have side effects, and allergies can be difficult or impossible to predict, but there have been no serious problems associated with inactivated polio vaccine.
Talk to your doctor if you have any questions about polio or the vaccine. A simple vaccine is enough to prevent a frightening disease and protect the people around you.