It is well established that certain vaccines can lead to mild symptoms resembling the disease against which they provide protection. However, they almost never cause the full-blown disease.
The classic example is measles. The MMR vaccine contains a weakened (or attenuated) but live measles virus and can cause a rash in about 5% of people. This typically occurs about one week after immunisation.
Although this measles-like rash can be a source of anxiety for parents, the vaccine does not cause the more serious symptoms – such as inflammation of the middle ear or the lung – which are hallmarks of the actual disease. Most importantly, the much-feared measles encephalitis (inflammation of the brain) is extremely rate after immunisation. It occurs in about one in a million children after vaccination, but affects one in a thousand children who have measles.
In the past, most European countries recorded cases where patients developed poliomyelitis due to the live oral polio vaccine which was used. This vaccine has been largely replaced by an injection which doesn’t contain live viruses and will not cause the disease to develop.
On a separate note, you should be aware that vaccination can sometimes be followed by nausea, fever and drowsiness, along with some swelling and redness at the site of injection. These are just normal reactions of the body and usually subside quickly. They are not connected to the disease against which you are being immunised.
For more information, see ‘Vaccination – 20 Objections & Responses’, produced by the Robert Koch Institute and Paul Ehrlich Institute