Can polio vaccine cause polio?

To understand whether Polio vaccine can cause polio, we need to understand the different types of virus and the vaccines. Wild Polio exists in 3 types with type 2 being most efficient. So vaccines need to target all 3 types. There are two types of Polio vaccines which differ in their cost, efficiency, and mode of administration. 

First type is the Inactivated Poliovirus Vaccine (IPV) as it contains inactivated versions of polio virus. This is administered intravenously and need to be stored in a refrigerator. 

Second type is the Oral Polio Vaccine (OPV) as it is administered orally and is lower in cost. OPV contains attenuated versions of polio virus which can revert to being virulent at times in turn causing polio. This is known as vaccine-associated paralytic polio (VAPP). 

Yes, you read that right - oral polio vaccine can cause polio! 

So why do we still use OPV when IPV is sufficient to trigger immune response without causing polio? OPV is mainly preferred for mass immunisation in countries where polio is still not yet eradicated as its low cost and ease of vaccine administration orally are essential for success of such campaigns. For every 200 cases of wild polio that is averted, 1 case of VAPP is inadvertently caused. This is the price to pay for total polio eradication.

However, in countries where polio is already eradicated they can switch over from OPV to IPV to eliminate VAPP and avoid vaccine derived poliovirus (cVDPV) reverting to wild type and start circulating in the population. This time however the prevailing herd immunity can prevent future polio outbreak despite vaccinations not covering the entire target population.

So in a country like India OPV was preferred until polio was eradicated in as late as 2014 after which it is better to switch to IPV to limit VAPP.

Reference:

[1] https://www.thehindu.com/opinion/lead/a-major-milestone-in-polio-eradication/article2796285.ece