Workers pack boxes of hepatitis B vaccine at Biokangtai, a bio-pharmaceutical company in Shenzhen, Guangdong province. Provided to China Daily

"WHO is confident about the safety and effectiveness of the vaccines used and manufactured in China," said Fabio Scano, head of disease control at WHO's China office.

Scano said WHO has evaluated the authorities responsible for licensing and ensuring the safety and effectiveness of vaccines used in China, and has concluded that they are fully functional, thus confirming that vaccine regulation in China meets international standards. "WHO periodically reassesses the vaccine regulatory system in China and other countries to assure that it remains of high quality," he said.

Tao Lina, a vaccine expert from the Shanghai CDC, said: "Myths about vaccine safety can confuse parents, who are simply trying to make sound decisions about their children's health. The problem is that the myths sometimes lead to parents ignoring the much higher risk of their children contracting life-threatening diseases without immunization because they worry too much about the very rare chance of an adverse event (side effect)."

Although they are designed to protect patients from disease, it's no secret that vaccines can cause side effects. However most are mild, such as soreness, swelling, or redness at the injection site.

Some vaccines are associated with fevers, rashes, and aches. Serious side effects are rare, but they may include life-threatening allergic reactions or seizures, and while vaccines may occasionally cause nausea or adverse reactions, in most cases the problems are unrelated, coincidental events.

Helping a larger proportion of the population to understand the necessity of vaccination is a difficult task, especially among two groups at opposite ends of the social spectrum - intellectuals and poorly educated people from rural areas, according to Wu, the Beijing CDC official.

"The former may think more about the safety aspects because they have more access to information from the media or via the Internet. And unfortunately, some of the information, especially that published in online chat rooms, is unreliable" Wu said.

He added that it's essential to emphasize that adverse events after immunization don't necessarily indicate a problem with the quality of a vaccine, and that side effects shouldn't be regarded as "unusual" occurrences.

Wu's analysis is corroborated by the US Centers for Disease Control and Prevention, which has stated that severe post-immunization side effects are extremely rare and only occur approximately once in 1.1 million doses.

Education intensified

This year, the NIP is intensifying its public "immunization education" plan, and from April to late July, medical professionals will deliver regular public lectures at hospitals and residential clinics.

In addition, testing has begun on a number of "combination vaccines" - single shots that can safeguard against several illnesses - that are likely to be widely recommended in China in the next five to 10 years.

"Combination vaccines are an excellent option for babies and for children who are scared of needles," said An Zhijie, director of the NIP.

An admitted that China's immunization program still has room for development; compared with the US program, which covers a wide range of the population from infants to adults, children younger than 6 are the major group targeted in China.

Beijing is in the vanguard of the program, expanding coverage from local children to migrant workers and their children. The Beijing CDC estimates that the number of people who have been vaccinated under the program has risen to "tens of thousands", especially as free vaccines have been available at schools and construction sites.

"Many of the migrant workers had never been vaccinated before," said Wu.

"That's the big paradox in promoting immunization - the better the achievement, the more the public is ignorant of the dangers posed by these preventable diseases, and that means our work appears to be of little value to some people. Occasionally that makes us all feel low, but the bottom line is that our work, whether it's appreciated or not, will help to make China a much healthier country, so it's worth making every effort."

Contact the author at yangwanli@chinadaily.com.cn