In 2010, bad vaccine scandals occurred in Shanxi, Guangdong and Jiangsu provinces, generating widespread panic among parents.

According to doctors, however, people should thoroughly consider their options before they decline all optional vaccination.

"Like any other medication, there are possible risks and side effects associated with vaccination," says Zhang Wenli, a senior pediatrician with No 3 Hospital of Peking University.

"The most common side effects like fever or rashes are mild, and go away within days. Vaccines can prevent serious or deadly diseases."

Zhang quotes an outbreak of polio in Xinjiang Uygur autonomous region in 2011 which killed one person and paralyzed another 17 patients, including eight children. The infection had been brought in from abroad.

"If more than 85 percent of Xinjiang residents had been vaccinated against polio, that tragedy could have been avoided," Zhang Wenli says.

While it can be tragic for the rare individual who develops a severe reaction to a vaccine, generally the chance of that occurring is less than one in a million, Zhang adds.

"It is understandable that people are unwilling to put their children at risk, or they think it is unnecessary to spend money on optional vaccination, but nothing is better than efficient prevention."

Zhang Wenli suggests parents should carefully weigh the possibility of the disease against the risks of vaccination and decide whether to get their children vaccinated, rather than to turn down all optional vaccines.