Pakistan does have the technology and facilities to conduct tests and figure out the composition of Polio Vaccines, and that's how it goes through as well. Checking composition of common medicinal liquids is basic. Drug Regulatory Authority of Pakistan and Pakistan Council of Scientific and Industrial Research, to name a couple, have the ability to conduct such tests. Apart from that, the composition can be tested in a laboratory of a hospital as well with appropriate equipment and reactants. You can get the Tests done from Private laboratories as well. The Polio Vaccines are bought by Government of Pakistan, tested by the Drug Regulatory Authority of Pakistan and thereafter redistributed among the masses.
https://tribune.com.pk/story/821038...-rules-out-use-of-fertility-harming-material/
In case your question is regarding the process to check whether or not the vaccine is harmful for the reproductive system and how simple it may be; we know which hormones and proteins (combinedly can be said to be fertility agents) can mess about with the biological reproductive system of humans, so a method is to use 'artificial' antibodies which are 'specific' to those agents, these antibodies when added would 'mark' the agents, if they are 'marked' then their presence has been confirmed, is there no change or observation, then the non presence of the agents is confirmed.
Are there any general side effects? Yes, Injected Polio Vaccine is safe, the only side effect being temporary pain and inflammation. However, Orally provided Polio Vaccine can reform to another molecule which can cause paralysis or other neurone issues, however it's extremely rare, according to Wikipedia, of all polio vaccination cases recorded, it is 3 in 1 million, which means a 0.0003% chance, so it's pretty safe. However, Orally provided Polio Vaccine provides better local immunity.
As for not 'trusting foreign medicines or imported medicine or vaccines', well; that is where how a scientific research is conducted comes into place. All scientific tests which are made are recorded in form of articles as well as tables, have 20 to 30 page long reports which are often published, have observations and anomalies and whatever need be mentioned, and they are 'reproduceable', meaning they can be re done anywhere in the world with appropriate equipment and you would achieve the same results.
Further details, such as what is the exact composition of the Polio Vaccine which is given orally as many people seem to question it and say that 'we don't know', except we do know;
The composition of Orally Administered Polio Vaccine includes water, culture media, stabilizing agents, traces of antibiotics and weakened strains of the polio virus.