The secret of the egg

(China Daily)
Updated: 2009-11-26 10:46

A worker of Sinovac Biotech Ltd moves Hy-line White eggs to light-checking room.

Several small white houses stand in rows in a suburban area of Haidian district. Inside, hundred of workers in blue uniforms and hats scamper around like frantic ants. Welcome to Sinovac Biotech Ltd, the producer of China's first new vaccine for A/H1N1 flu. METRO's reporter Yang Wanli finds out what mysteries hide in the vaccine everyone is talking about.

It's just a simple egg

Science can sometimes be deceptively simple. Every miniature bottle on the production line in Sinovac Biotech Ltd is the result of a highly complex technique, but the core ingredient for that process is nothing more irregular than a simple egg.

"The eggs we use differ from normal edible eggs. They are produced by a kind of chicken called the Hy-line White, which is normally used for medical and scientific research," said a worker in the egg inspection unit.

"Our chickens are provided with pollutant-free food and purified water. Their coops are kept very clean and no one is allowed to enter except the keepers."

The sole responsibility of the hens is to get pregnant. Only impregnated eggs can be used to make vaccines. The price for one Hy-line White egg is 2 yuan, about 6 times higher than a regular egg.

Impregnated eggs form the matrix of the virus. After 10 days, the embryo becomes a perfect environment to feed the virus.

Workers in a darkened room then use flashlights to check the inside of the eggs, ensuring only perfect eggs are selected for the procedure.

"Hy-line White eggs are white, which makes checking possible. We only select healthy eggs with good embryos and clear blood vessels," said the worker.

A strain on the egg

Once the egg is ready, workers inject the viral strain into the embryo sac. From this point on, the strain begins its own journey of reproduction.

"The viral strain is different from the A/H1N1 virus because it is reorganized and safer to the human body, and it was provided by the World Health Organization," said Liu Peicheng, media relation director of Sinovac Biotech Ltd.

"This viral strain will replicate itself and finally provide sufficient quantities for the vaccine."

However, growing inside an egg doesn't necessarily imply the viral strain is safe. After three days of development, all eggs receive a thorough check.

Although the strain has a radius of 80 to 120 nanometers, or about 1/500 the width of a strand of hair, it is already strong enough to kill a chicken embryo.

Weak embryos are picked out from the inspection and thrown away.

Machines finally remove a small piece of the shell and the virus and other liquids are sucked out by a hypodermic needle.

Time to harvest the goods

The virus is still not ready to produce a regular vaccine. It first needs to be deactivated and purified, to modify it from a mini killer into a mini lifesaver.

"A deactivator can limit the power of those viruses. After being deactivated, the virus will lose its capacity to hurt people," Liu said.

Because the deactivated liquid is still a mixture that contains other elements, it then needs to be purified.

After passing through pipes and sieves, the liquid is run into a filtering centrifuge.

Most of the impurities are filtered out, leaving a concentrated liquid infected with the virus.

Added next is a special material called a cleavage agent, which splits the virus into smaller pieces.

"At that point we can remove nucleic acids and macromolecular proteins, leaving behind surface antigens and the antigen protein that will arouse the body's immune system," Liu said.

Following the sterilization and filtration period, the antigen-loaded liquid is diluted with water and topped up with a little salt. It's almost ready.

Packed and stacked on ice

The vaccine fills 3-cm glass bottles that have already been washed by water and highly compressed steam three times and sterilized at 350 C.

These bottles are put on the production line and seven cameras pointing in different directions double-check them for impurities.

Next comes the packing. 20 bottles are put in a box and on it is printed a digital number which records the date and place of production. This is the box's unique identity.

"The vaccine needs to be stored between 2 C and 8 C in order to keep the antigens active," Liu said.

Then 10 boxes of vaccines are put into a special bag loaded with ice to keep them at a low temperature.

Liu said the company has special packing cases for those bags.

And workers will conduct random quality control check on vaccines.

And that's it.

Finally, after an amazing journey from egg to intricate blend of science, millions of antigens are ready to power up your immune system against the virus of the moment.