As most folks know, neither the DPT nor OPV vaccines are used in the United States.
That they are still used in other countries likely raises some questions for those folks that get them.
As I am sure you have guessed, there is no conspiracy about the continued use of these vaccines in other parts of the world. We aren't getting rid of old stocks of vaccines or using cheaper vaccines in poorer parts of the world.
To understand why they are still used in other countries, it helps to understand why they aren't used here.
Remember that the DPT vaccine, which protects folks against diphtheria, pertussis, and tetanus, came under attack in the 1970s and 80s as some folks blamed the vaccine for causing vaccine injuries, including seizures and encephalopathy. It didn't, but we still got a new vaccine, DTaP, which doesn't seem to work as well.
The OPV vaccine, on the other hand, was replaced because it can rarely cause vaccine-associated paralytic polio (VAPP) and circulating vaccine-derived polio virus (cVDPV). Of course, it does it at much lower rates than wild polio virus, so until polio is well controlled, the benefit of using OPV outweighs the risk. In addition to being less expensive and easier to use, OPV has the benefit over IPV of providing better herd immunity.
At some point, as we did in the United States in 2000, countries make a switch to the IPV vaccine.
In 2016, remaining countries that use OPV switched from trivalent OPV to bivalent OPV, because wild polio virus type 2 was eradicated in 1999. Once the remaining two types are eradicated, we can stop using the OPV vaccine altogether.
So there is no conspiracy. These vaccines are safe and they work.
With most of these cases affecting young children.