Recently, the news that a "SARS (Severe Acute Respiratory Syndromes) vaccine had entered into a stage of human testing" aroused wide interest from the media and the public. Many people offered to take part in the test for free. Questions such as the selection standard of volunteers, testing methods as well as the possible risks they face have become the most concerned questions of volunteers. Here some of the questions are answered.

1. What's the selection standard of volunteers?

Volunteers are young and middle-aged people of a normal healthy status.

So far, relative departments haven't formally publicized the detailed health standards for volunteers taking part in the SARS vaccine test. Although according to Guangdong Disease Prevention and Control Center, they haven't got the formal notice of recruiting volunteers for the test, it is reported the recruitment of volunteers will mainly focus on Beijing and Guangdong because these two places were the most severe SARS-affected areas, no matter if in terms of the number of SARS patients, suspected cases or those who had had contact with SARS patients.

A SARS research expert gave a description of a volunteer profile when interviewed by a reporter from the Beijing Youth Daily: first of all, the volunteer must be healthy without any symptoms of catching a cold or fever or any other abnormal symptoms. The recruitment will focus on young and middle-aged people and give attention to people of other age groups as well. According to the previous experience of vaccine testing on humans, the volunteer must have a "normal healthy status", meaning not especially strong or especially weak. Only by this will the test results have universality.

2. What methods will the test use?

One will be to check whether antibodies occur after inoculation. Another is a comparison experiment.

In what way will volunteers take part in the test? According to work staff in the administrative office of Guangdong Disease Prevention and Control Center, theoretically, there are two ways for some kind of vaccine to be used on human testing: one is to inoculate the vaccine into the body of the volunteer and observe if the human body will produce antibodies to the virus; the second is a comparison test, that will divide volunteers into two groups, one group being vaccinated, the other group not  vaccinated, and then observe if the two groups of people have the same reaction towards the virus under the same conditions. If the infection rate of those vaccinated people reduces greatly, it means the vaccine is effective.

"It is only theory," explained a staff member. "As to whether the SARS vaccine test on humans will take the two methods at the same time, it has not been confirmed yet. However, the first kind of test (on blood serum) is necessary. And it will be more difficult to conduct a comparison test. In addition, China has always been very prudent on vaccine testing on humans since it is closely related to our traditional morality and ethics."

Guangdong Disease Prevention and Control Center briefed on the previous promotion procedures of the measles vaccine. After the measles vaccine was developed, only people in a few experimental areas had been chosen to accept the inoculation. After a period of time of observation, the incidence of measles in the experimental areas was much lower than other non-experimental areas. Then the vaccine was gradually extended to other areas. And after many years' research, only when it was proved that the vaccine had no side-effects on children, China started to vaccinate new born babies around the country.

3. Will "lab infection accident of Singapore" reoccur in China?

Inactivated vaccine is totally different from the virus used for research and will not cause a SARS infection.

Many readers have called to ask about a SARS researcher in Singapore that had been infected with the SARS virus. Would such a thing reoccur in this test on humans? "Absolutely not," confirmed staff in Guangdong Disease Prevention and Control Center.

She explained that generally the vaccines are divided into two categories, one is an inactivated vaccine -- obtaining the virus and handling it with a scientific method, makes the virus totally lose its potency that allows it to be inoculated into an organism. The pathogen microbes in it produce no damage to the organism. And the organism will have an immune reaction towards the antigen structure on the surface of the pathogen microbes. Another kind is an attenuated vaccine, where some of the virus, after being inactivated and inoculated into the body, cannot help the body to prevent the disease. On the contrary, it worsens the patient's condition when the virus invades. Therefore, more time has to be spent on researching and developing an attenuated vaccine, that will make the virus propagate for many generations, sometimes even over hundreds of generations, and gradually get rid of the virus, and make it into a vaccine. Therefore the attenuated vaccine has higher requirements on the technical level.

According to Guangdong Disease Prevention and Control Center, the "prime criminal" which caused the SARS infection of a researcher in Singapore is a SARS virus used for research in the lab, and what we call the "wild virus", which has a very strong infection rate and propagation ability. It is totally different from the vaccine we are now talking about.

It is reported that currently the SARS vaccine for human testing that is approved by relative departments all belong to inactivated vaccines.

4. When can we say a SARS vaccine has been successfully developed?

After human testing, it has to stand the test of clinical application.

A SARS vaccine entering into a stage of human testing does not mean the vaccine has been successfully developed.

According to relative experts, the testing of ordinary vaccines must go through three stages: one, animal testing that inoculates the vaccine into an animal and then inoculates the SARS virus and observes the interdictive effect of the vaccine towards the virus. Currently, China has finished the research of this stage. The second stage is to test the vaccine on volunteers. The third is clinical testing, which is the key stage of testing if the vaccine has been successfully developed or not. Generally speaking, it should take two years.

According to experts, the developed vaccine must also pass one examination of an epidemic disease after going through the aforesaid three stages. Only if it is proved to be able to prohibit the spread of the virus and guarantee the health of humans, can it reach the application period of batch production. Even at the application stage, the vaccine is not absolutely safe without any problems. The prevention rate of general vaccines is hard to reach 100 percent. The prevention rate of most vaccines is over 90 percent, even if the very successfully developed vaccine may be effective in this group of 100 people, but only effective to 90 or 98 people among another group.

Facing the great concerns of the public towards the SARS vaccine, Guangdong Disease Prevention and Control Center also reminded that the SARS vaccine test on humans is a serious matter, even if finally the vaccine is successfully developed,  thinking of SARS as "no longer coming back" is not realistic.

For an infectious disease, besides preventive inoculation, comprehensive prevention measures are very important. That is why relative departments are speeding up the establishment of the public health system, seizing every minute to study a SARS vaccine.

(China.org.cn by Wang Qian and Daragh Moller, December 2, 2003)