Some history about the smallpox vaccine

As many older adults may recall, smallpox vaccine was once given as a part of routine childhood immunizations. At the time, few cancer patients were vaccinated, and acquired immunodeficiency syndrome (AIDS) was unheard of. Smallpox vaccination in the United States was stopped in 1972 because there had been no reports of smallpox since 1949. Because of the widespread immunization, the virus was wiped out in the United States. By 1977, smallpox was done away with in the rest of the world through careful tracking of every case and vaccination of all possible contacts (people who had been exposed to the person with smallpox).

At that time, experts believed that the only samples of smallpox virus left in the world were in the former Soviet Union and the United States and these were tightly guarded.But since 2001, it has been thought that other countries or groups might have kept or gotten smallpox virus, and could use it as a weapon. Because of this, the US government set up a program to vaccinate certain health care workers and military personnel.

In 2007, the Food and Drug Administration approved a newer version of the smallpox vaccine (called ACAM2000™) . It replaced the older Dryvax^® vaccine. The new vaccine seems to work as well as the older one. Side effects are also much the same and the same precautions apply.

Like the older vaccine, the newer one is to be used only in people who have a high risk for infection with smallpox. The vaccine is not available to the general public at this time. As of early 2009, the only people who may get the vaccine include the following:

• certain military staff
• those selected by state public health preparedness programs
• people who work in labs that handle smallpox virus

The vaccine

The vaccine against smallpox uses a live virus called vaccinia. It is not the smallpox virus, and you cannot get smallpox from the vaccine. The vaccinia virus is a lot like the smallpox virus, but rarely causes illness. Infection with the vaccinia virus makes a person immune to the smallpox virus.

When children got the smallpox vaccine as part of their routine childhood immunizations, only a few became ill from it. Most of the children who did get sick already had skin problems such as burns, impetigo, or eczema. The vaccinia virus would infect these breaks in the skin, which led to serious infections in some children that in rare cases caused death.

Another group of children who had inherited diseases that caused weak immune systems also had trouble with the vaccine. These children were not able to produce an immune defense to the usually-mild vaccinia infection, and some became seriously ill and died.

Serious and sometimes fatal illnesses have also happened when children with undiagnosed leukemia or lymphoma were vaccinated.

Doctors have raised concerns about the way vaccines could affect people with weakened immune systems if widespread vaccination is ever needed. Patients with poor immune function may find it hard to avoid being exposed to vaccinated friends or family members.

The vaccine can cause problems for people with weakened immune systems

People whose immune systems are not working well are most likely to be harmed by the vaccine. People with poor immune function are said to be immunosuppressed. This includes people with certain illnesses:

• those with certain chronic diseases such as liver disease, lupus, or other problems that affect the immune system

• those who have had organ transplants, including stem cell or bone marrow transplants

• those who take medicines that suppress the immune response

• those with HIV infection

• most people with cancer -- especially those being treated and those who have had bone marrow or peripheral blood cell transplants.

A recently vaccinated person can also infect people with the vaccinia virus. A vaccinated person can shed virus from the vaccine site for up to 21 days after the vaccination. Vaccinia can be spread by touching a vaccination site before it has fully healed. It can also be spread by touching bandages, towels, washcloths, or clothes that have picked up live virus from the vaccination site. Vaccinia is not spread through the air.

There have been many reports of people who got a vaccinia infection from vaccinated people. Most of the time, these people already had skin problems such as eczema, sores, or broken skin. Touching something that had vaccinia virus on it allowed the virus to invade these areas where the skin was open. Sometimes people became infected because of prolonged close contact with a person who was recently vaccinated. Any person whose immune system is not working well should be careful to avoid contact with people vaccinated within the last 21 days (see information below about contact).

Health care workers can also transmit the vaccinia virus within 21 days of vaccination. But this should be a minor problem since these workers can cover their vaccination sites. In a few cases, they may be given time away from caring for patients, especially patients with skin problems or immune deficiencies.

Larger problems may happen if the general public is vaccinated at some point in the future. People with poor immune function may find it hard to avoid being exposed to those who were recently vaccinated.

Questions and answers

Which cancer patients should avoid the vaccine?

Any cancer patient whose immune system is not working well should not get a routine smallpox vaccination because of the increased risk of serious side effects. This means that any person being treated or having recently been treated for cancer -- especially with chemotherapy or radiation -- should not get the vaccine (unless a smallpox outbreak occurs and they have already been exposed to smallpox). Patients who have no immune system problems may be able to get vaccinated. Talk to the doctor who is treating your cancer, or with your cancer care team to find out what is best for you.

What kinds of precautions should cancer patients take?

People with cancer should avoid close contact with people who recently have been vaccinated unless the vaccination site is covered with a gauze bandage and a special dressing (called a semi-permeable dressing). As of early 2009, the people most likely to get the smallpox vaccine include certain military recruits and laboratory workers.

If a person with cancer gets a vaccinia infection, symptoms might include rash, fever, and head and body aches. They should see a doctor who specializes in infections (an infectious disease specialist) as soon as possible.

What is "close contact?"

The CDC defines close contact as household or similar intimate physical contact. This means that anyone who has had a smallpox vaccination should not live with, share a bed with, or share bathing facilities with a person who has active cancer for at least 21 days after the vaccination. A person with cancer should not live with, or share a bed or bathing facilities with, anyone who has had a smallpox vaccination within 21 days of their being vaccinated. Because the virus is passed through direct contact, it is not likely that a person will become infected at the workplace, in public places, or by using public transportation.

The main concern for people who have close, physical contact with someone who has been vaccinated is that the vaccinia virus can be spread from the vaccination site. Vaccinia is spread by touching a vaccination site before it has healed and then touching another part of the body or touching someone else. It can also be spread by touching bandages, clothing, or other material that picks up live virus from the vaccination site. The vaccination site often becomes itchy, which may lead to scratching, rubbing, or touching the site. That increases the risk that the virus will end up on other parts of the body, or on clothing and other surfaces.

Are there other people who should not get the smallpox vaccine?

There are risks to getting the smallpox vaccine, and some people are at higher risk of having problems than others. A few of these risks are serious. If you live with or share a bed or bathing facilities with someone who has poor immune function (see above) you should not get the vaccine. People who have any of the following problems also should not get the vaccine.

• People with skin conditions that cause sores or breaks in the skin

• People who have short-term skin problems such as burns, poison ivy, acne, or other conditions causing broken skin should put off getting the vaccine until their skin has healed.

• People who have ever had eczema (atopic dermatitis), even if it is not causing problems at the time of the vaccination

• Women who are pregnant or may become pregnant within 4 weeks after getting the vaccine

• Anyone who lives with a person with one of the conditions listed above should not get the vaccine. If you share a bed or bathing area with a person who has one of these conditions, you shouldn't get the vaccine either.

People with the following health problems should also not get the smallpox vaccine. But there is no need to avoid the vaccine if someone in your household has one of these conditions.

• People who are allergic to any part of the vaccine, including certain antibiotics and latex, cannot take it.

• Women who are breastfeeding should not take the vaccine.

• People who are taking steroid eye drops or using steroid ointments in the eye should not take the vaccine.

• Anyone who is taking medicines that suppress the immune system should not take the vaccine.

• People with certain heart problems, or with 3 or more risk factors for heart disease, should not take the vaccine.

• People with moderate to serious illnesses should not take the vaccine.

What if a person is exposed to the smallpox virus?

The odds of actually being exposed to smallpox are very small, since there have been no cases for decades. But it is known that giving a person the vaccine even a short time after exposure gives some protection against smallpox.

For some people with cancer, the risk of having smallpox may become higher than the risks linked to the vaccine if they are actually exposed to smallpox. In the past, about 1 in 4 people with smallpox died, so the disease itself can be deadly. Even so, there are some people who still may not be able to get vaccinated even if they are exposed to smallpox. Anyone who has a reason not to get the smallpox vaccine should discuss the risks and benefits with a doctor.

For more information, you can find the CDC's information about smallpox and the vaccine on their Web site at: http://emergency.cdc.gov/agent/smallpox/disease/ or call them at 1-800-CDC-INFO ( 1-800-232-4636):TTY 888-232-6348.

References

Blendon RJ, DesRoches CM, et al. The public and the smallpox threat. N Engl J Med. 2003;348:426-432.

Breman JG, Arita I, Fenner F. Preventing the return of smallpox. N Engl J Med. 2003;348:463-466.

Brown A. for MILVAX, US Department of Defense. Health Care Provider's Briefing, 10 Oct 2008. Available online at: www.vaccines.mil/default.aspx?cnt=AdobeConnect/MultimediaDetails&SCO-ID=244237&GroupID=70163. Accessed December 30, 2008.

Centers for Disease Control and Prevention (CDC). Household transmission of vaccinia virus from contact with a military smallpox vaccinee--Illinois and Indiana, 2007. Morb Mortal Wkly Rep. 2007;56:478-481.

Centers for Disease Control and Prevention (CDC). Notice to Readers: Newly Licensed Smallpox Vaccine to Replace Old Smallpox Vaccine. Morb Mortal Wkly Rep. 2008;57:207-208.

Centers for Disease Control and Prevention. Smallpox: Information for Specific Groups. Available at: www.bt.cdc.gov/agent/smallpox/index.asp. Accessed December 31, 2008.

Centers for Disease Control and Prevention. Smallpox Vaccine Information Statement. Available at: www.bt.cdc.gov/agent/smallpox/vaccination/pdf/smallpox-vis.pdf. Accessed December 31, 2008.

Centers for Disease Control and Prevention (CDC). Vulvar vaccinia infection after sexual contact with a military smallpox vaccinee--Alaska, 2006. Morb Mortal Wkly Rep. 2007;56:417-419.

Food and Drug Administration. ACAM 2000 Questions and Answers, 2007. Available online at: www.fda.gov/cber/products/acam2000qa.htm. Accessed December 31, 2008.

Manufacturer's Prescribing Information: Acambis, ACAM 2000™. Available online at: www.acambis.com/documents/sites/1/Product_info/Package_Insert_final.pdf. Accessed December 31, 2008.

Wharton M, Strikas RA, Harpaz R, et al; Advisory Committee on Immunization Practices; Healthcare Infection Control Practices Advisory Committee. Recommendations for using smallpox vaccine in a pre-event vaccination program. Supplemental recommendations of the Advisory Committee on Immunization Practices (ACIP) and the Healthcare Infection Control Practices Advisory Committee (HICPAC). Morb Mortal Recomm Rep. 2003 Apr 4;52(RR-7):1-16.

Last Medical Review: 01/17/2009
Last Revised: 01/17/2009