Smallpox Vaccine Includes a Dose of Risk

Even though the last case of smallpox in the world occurred in 1978, the disease still haunts us through the threat of its use as a weapon of terror. Responding to the possibility that smallpox could be used as a weapon, the federal government has prepared an ambitious vaccination plan that starts with military personnel and hospital first-response teams.

The US and Russia retained small quantities of the virus after smallpox was declared eradicated in 1980. Many now believe that virus samples may have fallen into the hands of other governments, or terrorist groups, who could attempt to reintroduce the disease during military engagements or by exposing civilian populations.

In December of 2002 the federal government announced a plan to provide smallpox vaccinations for first-response teams in hospitals. Vaccinations of tens of thousands of military personnel have already begun, and further planning is underway to vaccinate the entire population of the United States should an outbreak occur.

But the smallpox vaccine itself can cause serious medical complications and even death in rare cases, which is why vaccination planning is proceeding with great caution. Michael J. Chusid, MD, Medical College of Wisconsin Professor and Vice Chair, Department of Pediatrics, and Chief of the Division of Infectious Diseases, discusses some of the ramifications of smallpox vaccination.

Dr. Chusid served as medical consultant to Children’s Hospital of Wisconsin and set up the hospital’s response to the federal vaccination plan. Dr. Chusid said that Children’s, Froedtert Hospital, and nearly every other hospital in Wisconsin volunteered to participate in the plan, which in turn asks for voluntary participation by health care practitioners.

Serious Consequences Demand Serious Consideration
“We have attempted to be very neutral in terms of recommendations regarding whether individuals should or should not receive the vaccine, because it’s a totally voluntary program,” said Dr. Chusid. “Now, as far as we know, there is no smallpox in the world. So, if you’re looking at risk versus benefit ratios, as long as there’s no case of smallpox the risk of the vaccine far outweighs any benefit. As soon as there’s a single case, then everything shifts because smallpox is a very serious and devastating disease.”

Smallpox is caused by the variola virus, which is spread from person to person through close contact. The disease can cause a severe rash that can leave scars when healed, high fever, tiredness, severe headaches and backache, blindness and death. According to the US Centers for Disease Control and Prevention (CDC), up to 30% of those infected with smallpox will die.

Smallpox vaccine is made from the vaccinia virus, which is similar to the smallpox virus but less harmful. According to the CDC, “Getting the vaccine before exposure will protect most people from smallpox. Getting the vaccine within three days after exposure can prevent the disease or at least make it less severe. Getting the vaccine within a week after exposure can still make the disease less severe. Complete protection from infection lasts 3 to 5 years, and protection from severe illness and death can last 10 years or more.”

Because the vaccine works even if given after exposure to smallpox, the federal government is recommending advance inoculation only for military personnel who might be put in harm’s way, and for a few first-response hospital personnel who may be called on to treat smallpox victims after an “event” such as a terrorist attack.

“Most people (in the public) will be in the same boat as the great majority of health care people – that is the post-attack boat – and you have three to four days to get the vaccine after being exposed,” said Dr. Chusid. “The vaccine beats the wild infection to the punch, so if you know you’ve been exposed you have several days in order to get the vaccination.”

Powerful Vaccine Can Cause Severe Complications
The CDC includes the following in its list of the risks that can accompany smallpox vaccination:

• Mild rash, lasting 2-4 days.
• Swelling and tenderness of lymph nodes, lasting 2-4 weeks after blister has healed (the vaccine almost always results in a blister).
• Fever of over 100 degrees in about 70% of children and 17% of adults.
• Secondary blisters elsewhere on the body (about 1 per 1,900 inoculations).
• Serious eye infection or loss of vision due to spread of vaccine virus to the eye.
• Rash on entire body (as many as 1 per 4,000).
• Severe rash on people with eczema (as many as 1 per 26,000).
• Encephalitis (a severe brain reaction), which can lead to permanent brain damage (as many as 1 per 83,000)
• Severe infection beginning at the vaccination site (as many as 1 per 667,000)
• Death (1-2 per million, mostly in people with weakened immune systems).

For every million people vaccinated, according to the CDC, between 14 and 52 could have a life-threatening reaction to smallpox vaccine. “Shedding,” the process of passing along reactions to the vaccine to people who have not received the vaccine themselves, can spread the risk. CDC cautions that people who come in direct contact with the vaccination site (usually the arm), or with materials that have touched the site, can have reactions as listed above from exposure to the vaccine virus.

As the government assesses evidence as to the possible possession of smallpox virus by those who would use it as a weapon, there is general agreement that it would be difficult, but not impossible, to spread the virus in quantities sufficient to expose masses of people.

One scenario has terrorists giving themselves smallpox and then entering the US to spread the disease through direct contact. Dr. Chusid noted, however, that the disease carriers would be obviously ill – “on death’s doorstep,” as he put it – during the period in which they could spread the disease, and thus would be fairly easy to spot. Another scenario involves the use of smallpox virus in a liquefied aerosol form to be spread through the ventilation system at a major airport, for example, so that the disease would appear in a variety of locations around the country.

According to the CDC National Immunization Program, there is enough smallpox vaccine in storage to inoculate the entire US population. The stock of vaccine is now stored in Atlanta, Dr. Chusid said, and a widespread public vaccination system could include distributing the vaccine to regional locations or major population centers.

Careful Screening of Vaccination Candidates
There is no immediate recommendation from any government agency to provide the vaccine to the general public. “We have received calls from people who want to be vaccinated,” Dr. Chusid said, “but the vaccine is not available. We don’t have any.” Dr. Chusid said that while a plan for nationwide vaccination is being formulated, implementation could be at least a year away and it is quite possible that general smallpox vaccination will never reappear as part of the American scene.

For now, the inoculation of troops and a small number of health care practitioners will provide new information about the impact of what is a very old vaccine. And new drugs may prove effective against smallpox or at least minimize the dangers inherent in using the current vaccine.

“If you thought there was a credible threat, then everyone should be inoculated,” said Dr. Chusid. “You bite the bullet and take whatever losses you have. Otherwise, why take any risk at all (in the general population) when you can do it after the first case shows up and inoculate everyone in the United States over a three or four day period?”

“There are potential problems with family members of inoculated individuals who get the virus and get some of the complications. The vaccination site, which is really a pustule, continues to shed live virus up to three to four weeks after you receive the vaccination,” said Dr. Chusid. “Say you have someone in your family who has eczema, or a young baby gets it in their eye, then they can get all the complications that we were worried about in the vaccinated person.

“We’re being very careful about the people that we’re vaccinating in this program. They have to have been pre-vaccinated before so they’re unlikely to have a reaction, they can’t have eczema, they can’t have immune-compromised conditions, and so forth. Additionally, no one in their families can have any of these conditions. So we’re looking very carefully at that group.”

Dan Ullrich
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.