Following up on China's high-profile vaccine scandal, a group of lawyers in the country are calling for more legislation to ensure vaccine safety.

In an open letter to China's congress, the lawyers said they want to see more stringent rules on vaccine supply chain management, plus better storage and administration requirements, as reported by Radio Free Asia (RFA).

The petition comes on the heels of a notorious illegal vaccine sales scandal in the country’s Shandong Province.

Pang Hongwei, the key participant in that mother-and-daughter crime ring, provided potentially unsafe vaccines to thousands of children from 2013 to 2015 and was recently sentenced to 19 years in prison. After the story broke, Chinese authorities arrested 324 people and removed or demoted 357 government officials.

The multimillion-dollar case exposed several loopholes in the country’s vaccine management regulations and supervision, prompting the government to update its supply chain regulations last April. The new rules cut off secondhand sales, allowing procurement of vaccines only directly from manufacturers and through provincial-level platforms.

According to the lawyers, though, the new regulations aren't effective enough in preventing future vaccine safety issues, such as low quality, incorrect vaccination processes, poor monitoring of adverse events, and more. Letter co-author Wang Shengsheng told the RFA that the country might see more scandals if the issues aren't addressed.

Because of the scope of the recent episode and the poor traceability of an already illegal conduct, the exact number of vaccines distributed and hence the number of children and families affected is hard to calculate, making it hard for them to claim compensation, the RFA report says.