Sarah Bennett
As global concern about monkeypox rises, many are wondering whether previous smallpox vaccination offers any protection. Smallpox vaccines were included in routine childhood vaccinations in the US until 1972, and the world was declared free of smallpox in 1980. Recent studies have shown that smallpox vaccination can provide some protection against monkeypox, with one study finding that smallpox vaccination provided 85% protection against monkeypox in close family household contacts. However, it's important to note that smallpox vaccination does not provide complete protection, and the level of protection may decrease over time. The protective immunity rate among those previously vaccinated against smallpox is still greater than the general population rate, but it is minimal, and previously vaccinated individuals can still contract monkeypox.
| Characteristics | Values |
|---|---|
| Are smallpox vaccines effective against monkeypox? | Yes, existing vaccines against smallpox are effective against monkeypox. |
| How effective are smallpox vaccines against monkeypox? | Smallpox vaccines provide partial protection against monkeypox. A study found that smallpox vaccination provided 85% protection against monkeypox in close family household contacts. |
| How long does immunity from smallpox vaccines last? | It is unclear how long immunity from smallpox vaccines lasts. One source mentions that the smallpox vaccine's effectiveness wanes over time, with a study finding that the longer the time since vaccination campaigns, the higher the incidence of monkeypox. |
| Are there any alternatives to smallpox vaccines for protection against monkeypox? | Yes, there are monkeypox-specific vaccines such as JYNNEOS (also known as Imvamune or Imvanex) and ACAM2000. |
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What You'll Learn
- Smallpox and monkeypox are part of the same family of viruses called orthopoxvirus
- Smallpox vaccines may provide protection against monkeypox
- Vaccinated people have a lower risk of contracting monkeypox than the general population
- The ACAM2000 smallpox vaccine can protect against monkeypox but has higher risks
- The JYNNEOS monkeypox vaccine is safer but has limited supply
Smallpox and monkeypox are part of the same family of viruses called orthopoxvirus
Smallpox and monkeypox (also known as mpox) are part of the same family of viruses called orthopoxvirus. Monkeypox is caused by the monkeypox virus, a species of the genus Orthopoxvirus, while smallpox is caused by the variola virus, which is also part of the Orthopoxvirus genus. Other members of this genus that can infect humans include the vaccinia virus, cowpox virus, and camelpox virus.
Orthopoxviruses are usually isolated from animals that are in close proximity to humans, such as cows, buffaloes, camels, monkeys, and rodents. The natural reservoir of the variola virus is only humans, while the natural reservoir of the monkeypox virus is various African rodents.
The World Health Organization (WHO) declared the global eradication of smallpox in 1980 and recommended discontinuing smallpox vaccination. This led to a loss of immunity against not only smallpox but also other orthopoxvirus infections, including monkeypox. The cessation of smallpox vaccination meant that a large portion of the world's population was no longer immune to these viruses, creating a new risk of circulation.
Since the eradication of smallpox, monkeypox has emerged and spread in central, east, and west Africa, with sporadic cases reported in other parts of the world, including the United States and Europe. The 2003 outbreak in the United States was the first opportunity to study human monkeypox outside of Africa and provided insights into the immune response and the role of previous smallpox vaccination.
Studies have shown that previous smallpox vaccination, especially in childhood, may not provide complete protection against monkeypox but can diminish disease severity and provide partial protection. The level of protection may depend on various factors, including age, time since vaccination, and immune response. However, the existing vaccines against smallpox are considered effective against monkeypox due to the close relationship between the viruses. The ACAM2000 vaccine, for example, can protect against smallpox and any other pox virus, like monkeypox, but it carries higher risks due to the possibility of viral replication and spread.
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Smallpox vaccines may provide protection against monkeypox
Smallpox and monkeypox are members of the orthopoxvirus (or poxvirus) family. Monkeypox is a rare virus that is endemic to central and west Africa. However, in 2022, cases of monkeypox began spreading throughout the world, causing concern about this virus to grow.
Since smallpox was eradicated over 30 years ago, smallpox vaccination rates have decreased, and the current clinical modelling study demonstrates that protective immunity to monkeypox is minimal. This means that most people are at risk of infection. However, the protective immunity rate among those who have previously been immunized against smallpox is still greater than the general population rate.
Studies have shown that smallpox vaccination diminishes the severity of monkeypox disease and provides 85% protection against the acquisition of monkeypox in close family household contacts. Furthermore, Dr Esper explains that "these members of the poxvirus families are so closely related that if you get immunized against any one of them, it actually protects against all the others". This means that existing vaccines against smallpox are effective against monkeypox.
The ACAM2000 vaccine, which has been around for a long time, is injected into the shoulder and causes an infection that the immune system then has to fight off, learning how to protect against smallpox and any other pox virus, including monkeypox. However, this vaccine comes with higher risks, as the virus can replicate and spread to other parts of the body. It is also not recommended for children under the age of 1, pregnant women, or people with certain conditions.
Another vaccine, JYNNEOS (also known as Imvamune or Imvanex), has a lower risk of side effects and requires two shots spaced four weeks apart. You are considered fully immune two weeks after your second dose.
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Vaccinated people have a lower risk of contracting monkeypox than the general population
The smallpox vaccine may offer some protection against monkeypox, but it is not a guarantee. Monkeypox and smallpox are different diseases, but they are both part of the orthopoxvirus family. This means that the vaccines for one disease can offer some protection against the other.
Studies have shown that smallpox vaccination can provide partial protection against monkeypox. For example, a study of the 2003 monkeypox outbreak in the US found that smallpox vaccination reduced disease severity and provided 85% protection against the acquisition of monkeypox in close family contacts. However, this study also showed that childhood smallpox vaccination does not provide complete protection against monkeypox in adults.
Another study, based on the current situation in Africa, found that the protective immunity rate against monkeypox among those who have been vaccinated against smallpox is higher than the general population rate. This suggests that vaccinated people have a lower risk of contracting monkeypox than those who have not been vaccinated. However, it is important to note that the protective immunity rate among smallpox-vaccinated individuals is still low, and there is a risk of getting the infection.
The ACAM2000 vaccine, which is the smallpox vaccine that has been used for some time, can protect against smallpox and any other pox virus, including monkeypox. However, this vaccine comes with higher risks, as the virus can replicate and spread to other parts of the body. The newer vaccine, JYNNEOS, has a lower risk of side effects and requires two shots spaced four weeks apart.
Overall, while the smallpox vaccine may offer some protection against monkeypox, it is not a guarantee, and the level of protection may vary depending on various factors. It is important to continue practicing other preventive measures, such as hand hygiene and social distancing, to reduce the risk of contracting monkeypox or any other infectious disease.
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The ACAM2000 smallpox vaccine can protect against monkeypox but has higher risks
The ACAM2000 smallpox vaccine can protect against monkeypox, but it carries higher risks. Monkeypox is a rare virus that is endemic to Central and West Africa. However, in May 2022, cases of monkeypox began to emerge in Europe and the United States, sparking global concern.
The ACAM2000 vaccine is a single-shot vaccine injected into the shoulder. It causes an infection at the injection site, stimulating the immune system to mount a defence. This immune response not only protects against smallpox but also offers cross-protection against other pox viruses, including monkeypox.
However, the ACAM2000 vaccine is associated with higher risks. The virus used in the vaccine can replicate and spread beyond the injection site, potentially affecting other parts of the body. As a result, individuals who receive the ACAM2000 vaccine must take precautions when caring for the injection site and avoid close skin-to-skin contact with others. It is also not recommended for children under one year of age, pregnant women, or individuals with certain health conditions.
While the ACAM2000 vaccine can provide protection against monkeypox, it is important to note that it does not offer complete immunity. Studies have shown that smallpox vaccination can diminish the severity of monkeypox and provide partial protection, reducing the risk of acquisition by close contacts. However, it does not guarantee full immunity, and vaccinated individuals can still contract monkeypox.
The protective immunity conferred by smallpox vaccination also wanes over time. The length of time since the last smallpox vaccination can impact the level of protection against monkeypox. As smallpox vaccination campaigns ceased decades ago, a significant portion of the population, especially younger individuals, lacks immunity to smallpox and, by extension, monkeypox. Therefore, while the ACAM2000 vaccine can offer some defence against monkeypox, it is not a foolproof solution, and other preventive measures and public health strategies are crucial to controlling the spread of the disease.
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The JYNNEOS monkeypox vaccine is safer but has limited supply
The smallpox vaccine may offer some protection against monkeypox, as the viruses are closely related. However, it is important to note that the level of protection provided by the smallpox vaccine is not fully understood and may vary depending on several factors, including age and time since vaccination.
The JYNNEOS vaccine is a newer vaccine that has been licensed in the United States to prevent both smallpox and monkeypox. It is a non-replicating modified Vaccinia Ankara virus vaccine, which means there is no chance of the live virus spreading to other parts of the body or to other people. This makes it a safer option than the older ACAM2000 vaccine, which can cause live virus generation and has been associated with higher risks. JYNNEOS is administered in two doses, given four weeks apart, and is approved for adults aged 18 years and older who are at high risk of smallpox and monkeypox infection.
While JYNNEOS appears to be safer, there are limited supplies available. The U.S. Department of Health and Human Services (DHHS) plans to distribute more than 4 million doses in 2022 and 2023. However, as of August 2022, there was a limited supply of JYNNEOS, and more research is needed to determine the durability and long-lasting immunity of the vaccine.
It is important to note that even with the limited supply of JYNNEOS, distribution to high-risk individuals is a priority. The CDC, HHS, and WHO are actively monitoring the situation and providing guidance on vaccine distribution and usage.
In conclusion, while the JYNNEOS vaccine appears to be a safer option for monkeypox prevention, its limited supply and the ongoing research into its efficacy and durability mean that distribution strategies and public health recommendations must be carefully considered.
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Frequently asked questions
Existing smallpox vaccines are effective against monkeypox. However, the level of protection depends on the time since vaccination, with immunity decreasing over time. A booster shot may be needed to ensure full protection.
Studies have shown that smallpox vaccination can provide up to 85% protection against monkeypox. However, the level of protection may vary depending on age and other factors.
The immunity conferred by the smallpox vaccine decreases over time. The length of time over which immunity lasts is currently unknown, but it is estimated to be several years.
