What our experts say
The AstraZeneca COVID-19 vaccine uses a chimpanzee adenovirus vaccine vector. A chimpanzee adenovirus vector is a genetically engineered virus that has been manipulated in a laboratory to change some of its traits so that it becomes harmless to humans. Scientists use a chimpanzee adenovirus as a vector - a way to get instructions for making virus-fighting antigens into the body - for several reasons. You can think of a vector like a car or carrier that delivers a message into the human body.
While chimpanzee adenovirus usually causes a common cold infection in animals, scientists used genetic engineering to prevent any disease from occurring in humans for COVID-19 vaccines. This means the adenovirus vector was engineered to become a harmless form of the virus that used to make chimpanzees ill but will not infect humans who receive the jabs.
Most adenoviruses only cause minor illnesses in humans. As a result, adenoviruses are thought to be safer than other types of vectors. They do not react to pre-existing adenovirus antibodies in humans that the body might remember and recognize the virus from previous infections it might have had before, like the common cold.
The adenovirus has been studied for decades. These studies show that adenovirus vaccines produce a strong immune system response, including memory cells that can help the body recognize the virus early. These results were found both for the COVID-19 vaccine and other vaccines previously developed.
Adenovirus was also chosen as a vector not just because of its ability to be genetically altered, but also because it allowed scientists to arm the virus with antigens specifically designed for COVID-19. Antigens are substances that make the immune system produce antibodies against it.
The modified chimpanzee adenovirus vector is purposefully armed with a portion of the COVID-19 virus's genetic sequence from its distinct spike protein. This allows it to enter the body so that the immune system can use the code to produce the spike proteins on its own which helps to prime the body against future exposures to COVID-19.
The AstraZeneca vaccine named the chimpanzee adenovirus vector used in its vaccine ChAdOx1 ("Ch" for chimpanzee + "Ad" for adenovirus + "Ox" for the University of Oxford where the vaccine was developed).
After three phases of clinical trials that included thousands of participants, this vaccine has been proven to be safe and effective in humans. Over 2 billion vaccine doses have been delivered to countries around the world with two-thirds of those going to low- and lower-middle-income countries.
However, a side effect called Thrombosis with Thrombocytopenia Syndrome (TTS) has been reported after some people received the AstraZeneca vaccine. TTS is associated with severe, unusual blood clotting events in addition to low platelet counts but is very rare.
Guillain-Barré syndrome (GBS) has also been reported very rarely following vaccination in some people. More studies are needed to determine the association between the vaccine and these events.
At this point, there does not appear to be a link between chimpanzee adenovirus vector and monkeypox. It should be noted that chimpanzees are not monkeys.
Monkeypox was first formally detected as a pox-like illness in laboratory monkeys (macaques) in 1958 by Preben von Magnus, hence the name 'monkeypox.' However, monkeys are actually not thought to be the primary hosts or carriers of the virus. The main disease carrier called the 'reservoir host' is still unknown.
It is possible that there were outbreaks of monkeypox before 1958 that were mischaracterized. One of these potential outbreaks was in 1949 in a Djakarta zoo and another was in Bengal, India in 1936.
African rodents are thought to be one potential cause of transmission but monkeypox has only even been isolated two times from animals in nature: in 1985 in a rope squirrel (a rodent) in the Democratic Republic of Congo and in 2012 in a dead mangabey (a primate) in Cote d'Ivoire.
The two outbreaks of monkeypox in 1958 that led to the formal discovery of monkeypox were observed in monkeys that arrived in Copenhagen from Singapore. Their skin erupted in lesions between 51 and 62 days after their arrival in Denmark and 20 to 30% of the monkeys developed infections.
The virus was discovered by Preben von Magnus during his research into pox-like symptoms among the monkeys who were being used in research for the development of a polio vaccine. Monkeypox did not spread to humans at this point in time and not all monkeys who were exposed to the virus were infected.
The first case of monkeypox in humans was documented in the Democratic Republic of Congo in 1970.
It is highly unlikely that monkeypox was caused by polio vaccine research given monkeypox is a double-stranded DNA virus, a cousin of the smallpox virus, and a member of the orthopoxyvirus viral family. Poliovirus is a single-stranded RNA virus in the Picornaviridae family. Many experts believe squirrels and other rodents are the natural hosts for the virus, not monkeys.
This idea likely started as some polio vaccines prepared between 1955 and 1962 were made using monkey kidney cells containing simian virus 40 which are not related to monkeypox.
Context and background
The monkeypox virus is usually found in tropical climates, especially in Central and West Africa, but recent outbreaks have caused the illness to spread to 11 countries with over 80 confirmed infections.
Monkeypox usually lasts around two to four weeks and causes people to develop symptoms including fever, rash, swollen lymph nodes, and may cause future medical complications. Other symptoms can include intense headache, back pain, muscle aches, lack of energy, and skin eruptions which can cause painful lesions, scabs, or crusts.
Usually, the virus is spread to humans in three ways: 1. From person-to-person (through close contact with body fluids, respiratory droplets, and lesions) 2. From an animal (zoonotic spread) 3. From the material that has been contaminated with monkeypox, meaning through close contact with objects like bedding and tissues where the virus is present
Monkeypox is similar to smallpox in a few ways. One is that symptoms caused by both viruses are similar and the vaccine used against smallpox, which was eradicated in 1980, has been shown to be roughly 85% effective at preventing monkeypox. In addition, an antiviral medication that was created to treat smallpox has also been licensed to treat monkeypox, which is called JYNNEOS (also known as Imvamune and Imvanex).
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- About the Oxford COVID-19 vaccine (University of Oxford)
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- Monkeypox Virus (Bacteriological Reviews)
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- Viruses that Can Lead to Cancer (American Cancer Society)
- Photo by Anna Shvets from Pexels
Used with Permission from Health Desk, a public health hub that explains emerging COVID-19 science.