CDC SMALLPOX FACT SHEET
People Who Should NOT Get the Smallpox Vaccine
(Unless they are Exposed to the Smallpox Virus)
Some people are at greater risk for serious side effects from the smallpox vaccine. Individuals who have any of the following conditions, or live with someone who does, should NOT get the smallpox vaccine unless they have
been exposed to the smallpox virus:
--Eczema or atopic dermatitis. (This is true even if the condition is not currently active, mild or experienced as a child.)
--Skin conditions such as burns, chickenpox, shingles, impetigo, herpes, severe acne, or psoriasis. (People with any of these conditions should not get the vaccine until they have completely healed.)
--Weakened immune system. (Cancer treatment, an organ transplant, HIV, or medications to treat autoimmune disorders and other illnesses can weaken the immune system.)
--Pregnancy or plans to become pregnant within one month of vaccination.
In addition, individuals should not get the smallpox vaccine if they:
--Are allergic to the vaccine or any of its ingredients.
--Are younger than 12 months of age. However, the Advisory Committee on Immunization Practices (ACIP) advises against non-emergency use of smallpox vaccine in children younger than 18 years of age.
--Have a moderate or severe short-term illness. (These people should wait until they are completely recovered to get the vaccine.)
--Are currently breastfeeding.
Again, people who have been directly exposed to the smallpox virus should get the vaccine, regardless of their health status.
Benefit of Vaccine Following Exposure
Vaccination within 3 days of exposure will prevent or significantly lessen the severity of smallpox symptoms in the vast majority of people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may modify the severity of disease. (This does not necessarily refer to immune compromised people).
If offered the smallpox vaccine, individuals should tell their immunization provider if they have any of the above conditions, or even if they suspect they might.
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Information on Live Virus Vaccines and Vaccinia
The vaccinia virus is the "live virus" used in the
smallpox vaccine. It is a "pox"-type virus related to
smallpox. When given to humans as a vaccine, it helps
the body to develop immunity to smallpox. The
smallpox vaccine does not contain the smallpox virus
and it cannot cause smallpox.
What is a "live virus" vaccine?
A "live virus" vaccine is a vaccine that contains a "living" virus that is able to give and produce
immunity, usually without causing illness.
Because the virus in the smallpox vaccine is live, it can be transmitted to other parts of the body or to
other people and so the site must be cared for carefully.
For most people with healthy immune systems, live virus vaccines are effective and safe.
Sometimes a person getting a live vaccine experiences mild symptoms associated with the virus in the
Other live virus vaccines used include measles, mumps, rubella, and chickenpox.
Facts about vaccinia
The vaccinia virus, the virus in the smallpox vaccine, is another "pox"-type virus.
Vaccinia is related to smallpox, but milder.
The vaccinia virus may cause rash, fever, and head and body aches. In certain groups of people,
complications from the vaccinia virus can be severe.
Vaccinia is spread by touching a vaccination site before it has healed or by touching bandages or
clothing that have been contaminated with live virus from the smallpox vaccination site.
This way, vaccinia can spread to other parts of the body or to other individuals. This is called
In the past, spreading to other parts of the vaccine recipientsŐ body was the more common form of
Careful care must be taken of the site of the vaccine to prevent spreading of the vaccinia virus.
Who should NOT get the smallpox vaccine?
People most likely to have side effects are people who have, or even once had, skin conditions, (especially
eczema or atopic dermatitis) and people with weakened immune systems, such as those who have received a
transplant, are HIV positive, or are receiving treatment for cancer. Anyone who falls within these categories, or
lives with someone who falls into one of these categories, should NOT get the smallpox vaccine unless they
are exposed to the disease. Pregnant women should not get the vaccine because of the risk it poses to the
fetus. Women who are breastfeeding should not get the vaccine. Anyone who is allergic to the vaccine or any
of its components should not get the vaccine. Children younger than 12 months of age should not get the
vaccine. Also, the Advisory Committee on Immunization Practices (ACIP) advises against non-emergency use
of smallpox vaccine in children younger than 18 years of age.
Reactions after Smallpox Vaccination
The smallpox vaccine prevents smallpox. For most people, it is safe and effective. Most people experience normal, typically mild reactions to the vaccine, which indicate that it is beginning to work. Some people may
experience reactions that may require medical attention.
Normal, Typically Mild Reactions
These reactions usually go away without treatment:
The arm receiving the vaccination may be sore and red where the vaccine was given.
The glands in the armpits may become large and sore.
The vaccinated person may run a low fever.
One out of 3 people may feel bad enough to miss work, school, or recreational activity or have trouble sleeping.
In the past, about 1,000 people for every 1 million people vaccinated for the first time experienced reactions that, while not life-threatening, were serious. These reactions may require medical attention:
--A vaccinia rash or outbreak of sores limited to one area. This is an accidental spreading of the vaccinia virus caused by touching the vaccination site and then touching another part of the body or another person. It usually occurs on the genitals or face, including the eyes, where it can damage sight or lead
to blindness. Washing hands with soap and water after touching the vaccine site will help prevent this (inadvertent inoculation).
--A widespread vaccinia rash. The virus spreads from the vaccination site through the blood. Sores break out on parts of the body away from the vaccination site (generalized vaccinia).
--A toxic or allergic rash in response to the vaccine that can take various forms (erythema multiforme).
Rarely, people have had very bad reactions to the vaccine. In the past, between 14 and 52 people per 1 million people vaccinated for the first time experienced potentially life-threatening reactions. These reactions
require immediate medical attention:
--Eczema vaccinatum. Serious skin rashes caused by widespread infection of the skin in people with skin conditions such as eczema or atopic dermatitis.
--vaccinia (or vaccinia necrosum). Ongoing infection of skin with tissue destruction frequently leading to death.
--Postvaccinal encephalitis. Inflammation of the brain.
People with certain medical conditions-including people with weakened immune systems or certain skin conditions-are more likely to have these reactions and should not get the smallpox vaccine unless they have been exposed to smallpox.
Based on past experience, it is estimated that between 1 and 2 people out of every 1 million people vaccinated may die as a result of life-threatening reactions to the vaccine.
Important Note: Statistical information about smallpox vaccine adverse reactions is based on data from two studies conducted in 1968. Adverse event rates in the United States today may be higher because there may be more people at risk from immune suppression (from cancer, cancer therapy, organ transplants, and illnesses such as HIV/AIDS) and eczema or atopic dermatitis. The outcome associated with adverse events may be less severe than previously reported because of advances in medical care. Rates may be lower for persons previously vaccinated.