Small Pox: Nobody Knows What is in the World's Most Dangerous Vaccine.

Historians and physicians typically think the vaccine is composed of the cowpox virus, a cousin of smallpox. But a closer investigation offers compelling new information that suggests the effective ingredient in the smallpox vaccine is another virus entirely.
A genomic analysis of a sample of the smallpox vaccine from 1902 provides evidence that the vaccine used to eradicate smallpox disease—which is caused by the variola virus—was made of  horsepox, a genetically similar but different virus entirely.

The new paper published Wednesday in the New England Journal of Medicine calls into question much of what we thought we knew about one of the most significant discoveries in early medicine. For the study, researchers led by the Robert Koch Institute in Berlin, Germany, obtained one of the earliest known samples of the smallpox vaccine from a private collection that was originally produced by H.K. Mulford Co. from Philadelphia. (After a merger decades later this manufacturer would become Merck & Co.)
“If a cow is inoculated with one of these three viruses it's very difficult to see the differences. In the past, any disease that would give pustular lesions would be called cowpox," Clarissa Damaso, an expert in virology and molecular biology from the Federal University of Rio de Janeiro, Brazil and coauthor of the study, told Newsweek. “This is the first time that we’ve proved scientifically that horsepox has been used for a smallpox vaccine."
Scientists have wondered about the origins of the vaccine before. According to the authors of the paper, some scientists analyzing a chicken embryo in the 1930s discovered the smallpox virus wasn’t the cowpox virus after all.
Smallpox, cowpox and horsepox are different viruses but the same genus. It is possible, says Damaso, that the cowpox and horsepox viruses were used interchangeably, without anyone's knowledge, to formulate the vaccine. The vaccines currently available for smallpox contain another virus that is now called vaccinia, and is not a direct match to either cowpox or horsepox.
Until now, scientists and historians believed the vaccine originated from the cowpox virus because Jenner famously formulated the serum after withdrawing fluid from the pustules of cow milkers infected with the virus that had come into contact with the sick animals. 

The Most Dangerous Vaccine

Smallpox may be the worst disease ever known to man. It killed about half a billion people from 1880 to 1980, before it was eradicated.
And the smallpox vaccine is deadly, too. Scientists call it the most dangerous vaccine known to man.
Today, smallpox is a potential weapon of mass destruction that could be wielded against the U.S. by enemies like Iraq and al Qaeda.
60 Minutes II Correspondent Dan Rather reports that in evaluating the potential danger of smallpox, the Bush administration has faced a deadly dilemma: Do not vaccinate the population against small pox and leave millions of people vulnerable to one of the worst scourges known to man. Or treat people with a vaccine that is extremely effective at blocking the disease but can cause dangerous, sometimes fatal, reactions.
The United States stopped giving mandatory smallpox vaccinations 30 years ago. Soon after that, doctors eradicated the disease from the planet. But now, the government has decided to bring back the vaccine because of fear that terrorists, or Iraq, could use the virus as a weapon.
The vaccine effectively immunizes against smallpox. But that protection has a price. Some people die from it; and others have serious reactions, some permanent. Scientists say it's the most dangerous vaccine known to man.
It could protect Americans from the unthinkable destruction of a smallpox attack. But the vaccine has a dark side.
"We know if we immunize a million people, that there will be 15 people that will suffer severe, permanent adverse outcomes and one person who may die from the vaccine," says Dr. Paul Offit, one of the country's top infectious disease specialists, and he knows all about vaccines that prevent those diseases. In his lab at Children's Hospital of Philadelphia, he studies and creates new vaccines. There's nothing new about the smallpox vaccine.
The vaccine was created in 1796. The vaccine used today is essentially the same, Offit says. "We tend to think of vaccines as being very safe and every effective, which they are. But all the vaccines that we use today are the result of modern technology. That's not true of the smallpox vaccine. It has a side effect profile that we, we would not accept for vaccines today," he says.
But once in a while, the vaccine does more harm than good. If you scratch where the smallpox is at the surface, and you put it to the eye, you can transfer the smallpox to your eye. That occurs in about 500 people for every million that get the vaccine. If you get "progressive vaccinia," your immune system is compromised. The virus just continues to grow and grow, and is often the cause of death.
No one is certain how many people will be hurt by the vaccine. A 1969 study found that, out of every one million people vaccinated, 74 will suffer serious complications, and at least one will die.
These side effects were never a secret, but they were rarely discussed, when the law required every child to get a smallpox vaccination before starting school.
If you did get the smallpox vaccine as a child, it may help you today. Some experts think you may still have some of your old immunity against the disease. But that's only a theory. There are no reliable studies on this, and other scientists disagree.
So why is the government recommending a dangerous vaccine that could kill people?
"Smallpox as a weapon is the biological equivalent of the nuclear bomb. It is simply the most dangerous biological weapon in the world," he says. That's because it spreads on its own, unless you stop it.
Offit thinks it's a mistake to vaccinate lots of people now, before there's any kind of outbreak. He thinks there's a safer approach: "Here's another way to do it. We can make the vaccine. Make sure we understand who's going to get it, who's going to be giving it. Then wait, wait for there to be one case of documented smallpox somewhere on the face of this earth and then we can move into vaccinating people, large numbers of people."
Israel wants to be prepared for a smallpox attack. In August, they immunized nearly 15,000 health-care workers. More vaccinations are planned. So far, there have been four bad reactions, two very serious. And some health care workers are unwilling to be vaccinated.
In the U.S., doctors are conducting a scientific study to find out just how people react to smallpox vaccines. Dr. Gregory Poland's staff at the Mayo Clinic started inoculating volunteers just a few weeks ago.
One of Dr. Poland's major concerns is making sure people don't spread the vaccine virus to other parts of their bodies, or to other people who haven't been vaccinated.
"What if a child touches it? A pregnant woman? Somebody with HIV infections? They could potentially die as a result," he says. 
The New York City Health department has been working for months to figure out exactly who should get inoculated, and when. Dr. Thomas Frieden, the health commissioner, estimates his department will have to vaccinate 15,000 New Yorkers very soon, and perhaps 300,000 more in coming months.
"The vaccine is not for the general public. It's only for those people who would be - in the case of a smallpox outbreak - would be responding to, and caring for, the initial cases," he says.
The first to be vaccinated, Frieden says, will be a team of health care workers at each hospital in New York. But some people should not be vaccinated.
"Some of the people who shouldn't get the smallpox vaccine are those who have a weakened immune system, including those who are HIV positive, those who have gotten cancer treatments, and those who have a transplant," he says.
Also included on that list are people with the skin-condition eczema, pregnant women and infants. Frieden's department has real-life experience with large-scale vaccination programs. More than 50 years ago, a tourist brought smallpox virus to the city, and health officials reacted quickly.
More than six million people were vaccinated in three weeks in New York City in 1947. There were 12 cases of smallpox. "There were two deaths associated with smallpox, and there were, I'm sorry to say, three deaths associated with the vaccine," he says.