All vaccines can result in some fever, general grumpiness and in some cases, pain at the site of the injection. This can be treated in the same way as any fever and pain, with paracetamol syrup and TLC. Serious side effects do occur, but they are extremely rare.
If your child has more than a mild viral illness when it is time to vaccinate, then vaccination will be delayed until they are better.
Pertussis vaccine is one which has received sufficient bad press to result in lack of vaccination in some countries, leading to outbreaks of whooping cough. There is a small, less than one in a million, chance of serious neurological complications from this vaccine. As a result it is never given to children who have a history of convulsions (except febrile convulsions) or of cerebral irritation or damage in the neonatal period. It is also never given to any child with an established disorder of the central nervous system, such as epilepsy, a history of collapse or shock, persistent screaming, fever over 40.5 degrees centigrade or a previous neurological reaction to the vaccine.
There have been recent reports of outbreaks of polio associated with the live polio vaccine. However, paralysis as a complication of the polio vaccine occurs in 1 in 3 to 5 million people who receive the vaccine, with a higher risk in adults than in children. The incidence of paralysis in naturally contracted polio is considerably higher, and in addition between 2 and 5% of children and 15 to 30% of adults with paralysing polio die.