As with any medication, no one can completely rule out the possibility of side effects associated with vaccines, but people can minimize the risks if they take appropriate measures, medical experts say.

Vaccines are not appropriate for certain people, and before receiving one, it is wise to look through the description which can be easily found online, or in the document a patient must sign before getting vaccinated at a hospital, says Zhang Wenli, a pediatrician and vaccination specialist with No 3 Hospital of Peking University.

"Even if vaccines have side effects, many of them can be avoided, especially severe ones," Zhang says.

The side effects occur when the immune system works against the foreign agent, and most side effects are mild, and fade in a few days.

However, if the person has an immune deficiency - either one they were born with or acquired from illness or drugs - the side effects will be more severe, and sometimes be life-threatening, such as the reported case of children getting polio after receiving polio vaccine, Zhang adds.

"It is important that people who have immunity deficiency, serious allergies and chronic diseases inform vaccination specialists of their condition," Zhang says. "Some people cannot get certain vaccines in certain circumstances. They should wait for another time, choose a safer version, or give up on such vaccination."

Vaccines are given to healthy people, often children, and people tend to spotlight their side effects and risks instead of their usefulness. Generally, vaccines are safe, notes Zhang Weina, a vaccination specialist with Beijing Tongren Hospital.

Testing and trials are always carried out to prove the efficiency and safety of a vaccine before it is licensed. Once licensed and in use, vaccines are distributed through centers of disease control, and are continuously monitored for safety and efficacy, Zhang Weina says.

China has had its vaccine regulatory system assessed as qualified by the World Healthy Organization, and some Chinese vaccine manufacturers have exported vaccines abroad.

If people are still concerned about the health risks, choosing vaccines that have been in use for a long time and have no reported large-scale adverse effects is one way to feel comfortable, medical experts say.

"Vaccines protect people against diseases and save lives," says Zhang Weina. "If vaccine producers and distributors follow strictly as the law requires, and people use vaccines under medical direction, there is no reason to worry about vaccination safety."