Side Effects of the Polio Vaccine

The polio vaccine that is being used today is quite safe. It is made from killed polio virus, and there is no live virus in any of the vaccines. It is impossible to contract polio from this vaccine. The vaccine-induced paralysis associated with the live polio vaccine is a concern of the past because the live polio vaccine is no longer used in the United States.

Common Mild Reactions

Common mild reactions can include a sore spot on his arm where your child received the polio injection, but often there will be no fever or rash from the injection. The soreness should resolve in less than two days.

Possible Allergic Reaction

Since the killed polio vaccine is prepared with a cell culture that is treated with antibiotics, the vaccine contains a trace amount of antibiotics — streptomycin, neomycin, and polymyxin B — that remains in the final product. These antibiotics are similar to the ones in the popular triple antibiotic ointment applied to cuts and scrapes (such as Neosporin).


Today's polio vaccine no longer contains SV40. Since the 1990s, a new method of vaccine production obviates any possibility of viral contamination in today's polio vaccines.

If your child is allergic to these antibiotics, a life-threatening reaction may occur that includes hives, difficulty breathing, and wheezing. This allergic reaction is very rare, estimated to occur less than one in a million doses.

The SV40 Controversy

Today's polio vaccine is largely out of the limelight for its safety concerns. The main argument against polio vaccination is whether it is still necessary. However, this has not always been the case. In the 1960s, the safety of the polio vaccine was hotly debated because a new virus was found to have contaminated over 10 million doses of the early polio vaccine.

When the killed polio vaccine was first invented (the Salk polio vaccine), scientists did not know much about viruses. The technology to detect viruses had not yet been invented. Between 1955 and 1961, vaccine manufacturers made polio vaccines using kidney tissues from rhesus monkeys. During the production process, the polio virus grew along side of other viruses present in monkeys. It was originally believed that during the process when the polio virus was killed, these other types of viruses perished as well. Scientists later ascertained that it was not the case.

One type of virus in particular has since come under scrutiny. Dr. Bernice Eddy of the National Institute of Health isolated a virus called SV40 (simian virus 40) in 1961 in the laboratory. She was surprised to learn that if she injected this virus into hamsters, all the hamsters developed tumors. Because of that finding, the government implemented new regulations to eliminate all traces of SV40 from future polio vaccines. However, there was not a recall, and additional doses of the contaminated polio vaccines were administered to children until 1963.


The injectable form of the polio vaccine (the Salk vaccine) was the primary source of SV40 contamination. About 10 million contaminated doses were given between 1955 and 1961. The oral polio vaccine (the Sabin vaccine) was mostly free of this virus, and it is estimated that about 10,000 contaminated oral polio vaccines were administered.

The ongoing controversy is whether SV40 can trigger cancer in humans. It is known that SV40 can cause cancer in a variety of animals, including guinea pigs, hamsters, and mice. In humans, the virus has been isolated from certain types of tumor cells, including a rare type of lung cancer called mesothelioma, a brain tumor (ependymoma), cancer of the bone (osteosarcoma), and certain types of lymphoma (non-Hodgkin's). Whether some of these cancers are caused by SV40 is not clear. Even though the virus was isolated from some of the tumor cells, many people with these cancers have no evidence that they were ever infected by SV40. The research is ongoing to investigate the possible link between this virus and cancer. However, when looking back to those who were exposed to this virus from the contaminated polio vaccine, there is no increased risk of cancer in this population.

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