What is smallpox vaccine?
Smallpox vaccine contains live vaccinia virus, a virus in the orthopoxvirus family and closely related to variola virus, the agent that causes smallpox. Immunity resulting from immunization with vaccinia virus (vaccination) protects against smallpox. In December 1999, a WHO Advisory Committee on Variola Virus Research concluded that, although vaccination is the only proven public health measure available to prevent and control a smallpox outbreak, current vaccine supplies are extremely
limited. The Committee also noted that, at that time, several countries were contemplating the need to produce more vaccine stocks. Now, a number of governments have chosen to examine their stocks, test their potency, and consider whether more vaccine is required.
A WHO survey conducted in 1998 indicated that approximately 90 million declared doses of the smallpox vaccine were available worldwide. Storage conditions and potency of these stocks are not known. Most existing vaccine stocks and the vaccine used in the WHO eradication campaign consist of pulp scraped from vaccinia-infected animal skin, mainly calf or sheep, with phenol added to a concentration sufficient to kill bacteria but not so high as to inactivate the vaccinia virus. The vaccine is then freeze dried and sealed in ampoules for later re-suspension in sterile buffer and subsequent intradermal inoculation by multiple puncture with a bifurcated needle. The seed virus (vaccinia virus strain Lister Elstree) used to produce the vaccine is being held for WHO by the WHO Collaborating Centre for Smallpox Vaccine in Bilthoven, the Netherlands.
The smallpox vaccine helps the body develop immunity to smallpox. The vaccine is made from a virus called vaccinia which is a "pox"-type virus related to smallpox. The smallpox vaccine contains the "live" vaccinia virus—not dead virus like many other vaccines. For that reason, the vaccination site must be cared for carefully to prevent the virus from spreading. Also, the vaccine can have side effects The vaccine does not contain the smallpox virus and cannot give you smallpox. Smallpox vaccination provides high level immunity for 3 to 5 years and decreasing immunity thereafter. If a person is vaccinated again later, immunity lasts even longer. Historically, the vaccine has been effective in preventing smallpox infection in 95% of those vaccinated. In addition, the vaccine was proven to prevent or substantially lessen infection when given within a few days of exposure. It is important to note, however, that at the time when the smallpox vaccine was used to eradicate the disease, testing was not as advanced or precise as it is today, so there may still be things to learn about the vaccine and its effectiveness and length of protection.
The smallpox vaccine is not given with a hypodermic needle. It is not a shot as most people have experienced. The vaccine is given using a bifurcated (two-pronged) needle that is dipped into the vaccine solution. When removed, the needle retains a droplet of the vaccine. The needle is used to prick the skin a number of times in a few seconds. The pricking is not deep, but it will cause a sore spot and one or two droplets of blood to form. The vaccine usually is given in the upper arm. If the vaccination is successful, a red and itchy bump develops at the vaccine site in three or four days. In the first week, the bump becomes a large blister, fills with pus, and begins to drain. During the second week, the blister begins to dry up and a scab forms. The scab falls off in the third week, leaving a small scar. People who are being vaccinated for the first time have a stronger reaction than those who are being revaccinated. After vaccination, it is important to follow care instructions for the site of the vaccine. Because the virus is live, it can spread to other parts of the body, or to other people. The vaccinia virus (the live virus in the smallpox vaccine) may cause rash, fever, and head and body aches. In certain groups of people (see the section, complications from the vaccinia virus can be severe.
There is a vaccine against smallpox and it was a key tool in the eradication of the disease. The vaccine does not contain the variola virus which causes smallpox , but a closely related virus called vaccinia. When this vaccine is given to humans, it protects them against smallpox. However, it can have very serious side effects, which in extreme cases can be fatal. It has therefore not been recommended for the general public since smallpox was eradicated. It is used to protect researchers who work on the variola virus that causes smallpox and other viruses in the same virus family (known as orthopox viruses). It could also be used to protect anyone else judged to have a high risk of exposure to smallpox. The vaccine cannot be used in people whose immune systems are not functioning properly.