Sarah Bennett
Smallpox is an infectious disease caused by the variola virus, which was declared eradicated in 1980. However, the possibility of the virus being used as a biological weapon has led to continued interest in the smallpox vaccine. The vaccine is made from the vaccinia virus, a similar but less harmful virus, and it helps protect individuals from smallpox by developing immunity. While routine vaccination has stopped, it is still recommended for laboratory workers at risk of exposure. The vaccine is effective in preventing smallpox infection, even if administered within three days of exposure, and may also offer some protection if administered 4-7 days after exposure. Multiple vaccinations produce higher levels of antibodies, but a single vaccination provides stable and long-lasting protection.
| Characteristics | Values |
|---|---|
| Effectiveness of the smallpox vaccine | Historically, the smallpox vaccine has been effective in preventing smallpox infection in 95% of those vaccinated. |
| Protection duration | Protection from smallpox lasts for about 3 to 5 years after vaccination, with decreasing immunity thereafter. |
| Post-exposure effectiveness | Vaccination within 3 days of exposure will prevent or greatly lessen the severity of smallpox in most people. Vaccination 4 to 7 days after exposure may offer some protection and decrease the severity of the disease. |
| Availability | There is enough smallpox vaccine to vaccinate everyone who would need it in the event of an outbreak. |
| Side effects | The smallpox vaccine has been associated with adverse events, making the reinstatement of routine pre-exposure vaccination policies unlikely. |
| Exposure symptoms | Initial symptoms include high fever, fatigue, headache, backache, and a rash that appears 2 to 3 days after the fever starts. |
| Incubation period | It takes 7 to 17 days for initial symptoms to appear after exposure, with an average incubation time of 12 to 14 days. |
| Contagiousness | Smallpox is not contagious until just before the beginning of the rash (2 to 3 days after fever starts). |
| Fatality rate | The fatality rate among those vaccinated less than 10 years before exposure is 1.3%; it increases to 7% for those vaccinated 11 to 20 years prior and 11% for those vaccinated 20 or more years before infection. |
| Eradication | The last naturally occurring case of smallpox was diagnosed in 1977, and the World Health Organization (WHO) certified the global eradication of the disease in 1980. |
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What You'll Learn
- The smallpox vaccine can prevent smallpox if given within three days of exposure
- Vaccination 4-7 days after exposure may offer some protection or decrease severity
- Smallpox vaccination produces antibodies and virus-neutralizing activity
- The smallpox vaccine is made from the vaccinia virus
- Smallpox was an infectious disease caused by the variola virus
The smallpox vaccine can prevent smallpox if given within three days of exposure
The smallpox vaccine is highly effective in preventing smallpox infection. In fact, it was the successful vaccination programme that led to the eradication of smallpox in 1980, making it the only human disease to have been eradicated to date.
The smallpox vaccine helps the body develop immunity to smallpox. The vaccine is made from a virus called vaccinia, which is another pox-type virus related to smallpox but is less harmful. The smallpox vaccine does not contain the smallpox virus and therefore cannot spread or cause smallpox.
Currently, the smallpox vaccine is not available for the general public. However, there is enough vaccine stockpiled to vaccinate everyone who would need it in the event of an outbreak. Smallpox was declared eradicated in 1980, and routine vaccination of the public ceased that same year. The last naturally occurring case of smallpox was reported in 1977, and the risk of contracting the disease today is extremely low.
Nevertheless, the possibility of the smallpox virus being recreated or used for nefarious purposes has raised concerns. A single confirmed case of smallpox would be considered an international emergency, and vaccination campaigns would be necessary to contain the spread of the disease.
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Vaccination 4-7 days after exposure may offer some protection or decrease severity
Vaccination 4–7 days after exposure to smallpox may offer some protection or decrease the severity of the disease. Smallpox is a highly contagious and deadly disease caused by the variola virus, which was declared eradicated in 1980. However, the possibility of the variola virus being used as a biological weapon has led to a continued interest in smallpox vaccination.
The smallpox vaccine is made from the vaccinia virus, a poxvirus similar to smallpox but less harmful. The vaccine helps protect individuals by stimulating the body to develop immunity to smallpox. Historically, the vaccine has been highly effective, preventing smallpox infection in 95% of those vaccinated. Studies have shown that the fatality rate among vaccinated individuals exposed to smallpox was significantly lower than among those who were not vaccinated.
When administered within 4–7 days of exposure, the smallpox vaccine may provide some level of protection or reduce the severity of the disease. This is based on past experience and historical reports of smallpox outbreaks, which indicate that the vaccine can offer protection for 3 to 5 years after the initial vaccination, with decreasing immunity thereafter. However, it is important to note that the literature on the timing of effective post-exposure vaccination is conflicting, and the decision to vaccinate after exposure should consider the incubation period of smallpox.
If you believe you have been exposed to smallpox, it is crucial to act quickly and seek medical advice. Close monitoring for symptoms is recommended, and isolation is necessary at the first sign of fever. While the smallpox vaccine may provide some protection or reduce severity when administered 4–7 days after exposure, earlier vaccination (within 3 days of exposure) is more likely to prevent or significantly modify the disease.
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Smallpox vaccination produces antibodies and virus-neutralizing activity
The smallpox vaccine is made from a virus called vaccinia, a poxvirus similar to smallpox but less harmful. The smallpox vaccine contains a live vaccinia virus, unlike many other vaccines that use a killed or weakened virus.
The smallpox vaccine protects individuals by helping their bodies develop immunity to smallpox. Historically, the vaccine has been effective in preventing smallpox infection in 95% of those vaccinated. Research has shown that the vaccine can prevent or substantially lessen infection when given within a few days of exposure to smallpox. Specifically, vaccination within three days of exposure will prevent or greatly modify the severity of smallpox in most people. Vaccination 4 to 7 days after exposure may offer some protection and decrease the severity of the disease.
The duration of protection provided by the smallpox vaccine has been a topic of interest. Studies of smallpox cases in Europe in the 1950s and 1960s found that the fatality rate among those vaccinated decreased as the time since vaccination decreased. The protection offered by the vaccine is believed to last for at least 5 years, with increasing protection achieved with subsequent revaccinations. However, cross-sectional epidemiological studies have suggested that a single smallpox vaccination may provide protection for longer periods, challenging the dogma that repeated inoculations are necessary.
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The smallpox vaccine is made from the vaccinia virus
The smallpox vaccine is made from a virus called vaccinia, which is a "pox"-type virus similar to smallpox but milder. Vaccinia is a live virus in the vaccine, not a killed or weakened virus like many other vaccines. The smallpox vaccine does not contain the smallpox virus and cannot give someone smallpox. However, the vaccinia virus is live in the vaccine, so people who are vaccinated must take precautions when caring for the vaccination site to prevent the virus from spreading to other parts of the body or to other people.
The vaccinia virus was first grown in cell culture in 1931 by Thomas Milton Rivers. In 1932, Ernest William Goodpasture, Alice Miles Woodruff, and G. John Buddingh grew the vaccinia virus on the chorioallantoic membrane of chicken embryos. The Texas Department of Health began producing an egg-based vaccine in 1939 and started using it in vaccination campaigns in 1948. The egg-based vaccine was also used widely in Brazil, New Zealand, and Sweden. In 1959, Lederle Laboratories began selling its Avianized smallpox vaccine in the United States.
First-generation smallpox vaccines consist of live, unattenuated vaccinia virus and can cause serious side effects in a small percentage of recipients, including death in 1–10 people per million vaccinations. The second-generation vaccines are also based on live vaccinia virus grown in the chorioallantoic membrane or cell culture. They carry the same side effects as the first-generation vaccines. The third-generation vaccines are based on attenuated vaccinia viruses that are much less virulent and have milder side effects.
One of the licensed smallpox vaccines in the United States, ACAM2000, is a second-generation vaccine derived from a clone of Dryvax, an earlier smallpox vaccine. ACAM2000 is manufactured by Emergent Product Development Gaithersburg, Inc. and is approved for active immunization against smallpox disease for people at high risk of smallpox infection.
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Smallpox was an infectious disease caused by the variola virus
Smallpox was an infectious and often deadly disease caused by the variola virus. It was eradicated in 1977, thanks to vaccination efforts, with no cases occurring since. Smallpox was a serious disease that spread through close, face-to-face contact, coughing, or sneezing. It caused a distinctive, progressive skin rash and fever, and about 3 out of 10 people infected with the disease died. Many survivors were left with permanent scars, especially on their faces.
There are two variants of the variola virus: variola major and variola minor. Variola major was the most common and severe form, causing a more extensive rash and higher fever. It was responsible for most smallpox cases and the majority of deaths, with a case fatality rate of over 30%. Variola minor, on the other hand, caused similar but less severe symptoms and had a historical death rate of 1% or less.
In addition to these two main forms, there were also rare and fulminating types of smallpox, such as the malignant and hemorrhagic forms, which were usually fatal. Hemorrhagic smallpox, for example, was accompanied by extensive bleeding into the skin, mucous membranes, gastrointestinal tract, and viscera. It occurred in approximately 2% of infections and was typically fatal.
The smallpox vaccine was developed in 1796 by Edward Jenner, who noticed that exposure to cowpox, a similar but less harmful virus, could provide immunity to smallpox. The modern smallpox vaccine is made from the vaccinia virus, a poxvirus similar to smallpox, and it helps the body develop immunity by creating a live infection at the vaccination site. While the vaccine has historically been effective in preventing smallpox infection in 95% of vaccinated individuals, its availability is currently limited and inadequate for a mass inoculation program.
Vaccination within 3 days of exposure to smallpox is highly effective in preventing or significantly modifying the disease. Vaccination 4 to 7 days after exposure may still offer some protection or reduce the severity of the disease. The protection offered by the vaccine typically lasts for about 3 to 5 years, after which immunity decreases, and revaccination is recommended.
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Frequently asked questions
Yes, the smallpox vaccine can be used after exposure to smallpox. Vaccination within 3 days of exposure will prevent or greatly lessen the severity of smallpox in most people. Vaccination 4 to 7 days after exposure may offer some protection and may decrease the severity of the disease.
The symptoms of smallpox include a high fever, fatigue, headache, backache, and a rash that spreads across the face, arms, and legs. After exposure, it takes between 7 and 17 days for symptoms to appear, with an average incubation time of 12 to 14 days. Smallpox is not contagious until just before the rash appears (2 to 3 days after fever starts).
The smallpox vaccine has historically been effective in preventing smallpox infection in 95% of those vaccinated. It is made from a virus called vaccinia, which is similar to smallpox but less harmful. The last naturally occurring case of smallpox was diagnosed in 1977, and the World Health Organization (WHO) certified its global eradication in 1980. Routine vaccination of the American public stopped in 1972.
