Another case of adverse reaction, which was already discharged from the hospital, was possibly caused by shock due to an allergic reaction.

The causes of the 17 deaths vary, including severe pneumonia, suffocation, kidney failure, severe diarrhea and congenital heart disease, added the circular.

Experts from WHO agreed with the CFDA inspection results.

"So far ... the main message is that there is actually no evidence to support that there is an issue with the product that has been distributed and used," Lahouari Belgharbi, a WHO expert in immunization, told China Central Television.

Fabio Scano, head of disease control at WHO's China office, said: "I would like to emphasize that the steps taken in the investigation are in line with the WHO recommendation. And we are happy to have been working together for the last couple of days to review the findings of the joint investigation by CFDA and the commission.

"It's crucial to reassure the public and also parents' confidence in the hepatitis B vaccine program, definitely one of the most successful public programs in China. And it has prevented millions of hepatitis B infections over the last two decades," he added.

Biokangtai and two other large companies have currently stopped production of hepatitis B vaccines, as they didn't pass a new good-manufacturing practice certification imposed by the CFDA by the end of 2013.

This has raised the public's concern over the quality of the company's vaccine.

However, Zhao Kai, a vaccine expert with the National Vaccine and Serum Institute, dismissed the concern.

"The GMP code needs constant revision, as it was also revised in 1998. The vaccine produced before the latest GMP standards took effect have passed official tests before entering the market, and were made according to the older GMP," he said.