ONE HEALTH Flashcards
What is a vaccine?
Vaccines are used to boost the immune system to protect against infection. A vaccine uses an active ingredient, such as a attenuated virus or viral protein, to artificially stimulate the immune system and create memory leukocytes without actually infecting the individual.
What is in a vaccine?
- Active ingredient- stimulates immune system
- Adjuvants- makes the immune response stronger- can be harmful in large quantities
- Preservatives and stabilizers maintain the vaccine quality and prevent contamination.
- Residual traces: Substances that are used during vaccine manufacture, very little in the final vaccine. Often the source of allergies.
- Water: the main ingrediant
What is herd immunity?
When a large number of the population is vaccinated, it is harder for an infectious disease to spread. This breaks lines of transmission. Heard immunity is the protective effect achieved when a certain level of vaccinations is reached, depending on the reproduction number of the virus.
Why is heard immunity important?
It provides protection for people who cannot get vaccinated, such as people allergic to the vaccine, or too elderly to receive the vaccine, or with other underlying health conditions.
What is the reproduction number?
Epidemiologic measure used to describe the contagiousness or transmissibility of an infectious disease. How many people one person will infect on average. It is estimated using complex mathematical models. An R0 number above 1 will lead to a growing number of cases, e.g. an outbreak. An R0 number around 1 is typical of an endemic disease. An R0 number of below 1 is the aim to end an outbreak.
What must a disease fit into in order to be eradicated?
- Disease must be stable- the agent of the disease must not evolve fast and overcome vaccine pressure (DNA virus)
- The vaccine must be safe and effective- cheap to produce, 1 dose, heat stable.
- The vaccine must grant lifelong immunity
- The disease must have an easy and reliable means of diagnosis- key symptoms allow for quick vaccination
- The vaccine must not have an environmental reservoir for it to persist in
What are the candidates for global eradication and why are they still around?
Polio virus: Close to eradication previously but live attenuated virus started reinfecting
Measles and rubella: MMR vaccine had false report claiming it as a source of autism, so vaccination level reduced.
What are replicating viral vaccines?
Living viral vaccines, have the ability to replicate. These include live attenuated vaccines: viruses replicated many times in an animal cell culture so they are not dangerous to humans anymore or viruses treated with UV light e.g. small pox, MMR, polio, yellow fever, or can be replicating viral vectors such as Ebola vaccine.
What are non replicating viral vaccines?
Taking part of the virus and using it to create an immune response. These include:
1. Inactivated whole virus: whole virus but inactivated so cannot replicate e.g. Polio, influenza.
2. Subunit: use a protein from the virus to allow the immune system to create antibodies
3. Virus like particle: shell of a virus without the genetic material e.g. human papillomavirus
4. Non-replicating viral vectors: a virus that causes infection but does not cause illness. This virus is genetically modified so it produces proteins for another virus- a vector delivering genetic material to a cell.
5. Nucleic acid: genetic material put into cell, which produces viral proteins allowing immune response, then degraded.
What are the advantages and disadvantages of replicating vaccines?
Advantages: very good immune response- very accurate to the real thing. A single dose often gives life long protection. Can stimulate mucosal antibodies.
Disadvantages: May restore virulence like polio, may not be appropriate for the immunosuppressed, some viruses cannot be grown in cell culture, these have a limited shelf life.
What are the advantages and disadvantages of non-replicating vaccines
Advantages: much safer, quicker and easier to produce.
Disadvantages: may be less immunogenic, may require adjuvants and boosters, and may not stimulate mucosal immune response.
What is the molecular biology of Mpox?
Mpox is a shaped virus with linear double stranded DNA. It is part of the pox viridae family meaning it is a pox virus so it replicates in the cytoplasm. This is the only DNA virus to do this. Each end of the genome has an inverted repeat region, which join up with each other and create a ring allowing for continuous replication. It is enveloped by the host membrane.
What is the difference between the mpox clades?
Clade I: less infectious, more deadly (16,000-3.6%). Endemic in central Africa- this clade can actively disable immune responses.
Clade II: more infectious, less deadly (92,000-0.3%). Endemic in west Africa.
When was mpox first discovered, when was the first case of it, and when did it reach the US?
Mpox was discovered first in monkeys in 1958 in Denmark. Mpox was first discovered in humans in 1970 in DRC. Mpox first spread to the US in 2003 due to exotic pet trade: Guinean rats
How was mpox first transmitted?
First spread to humans from monkeys- a zoonotic infection. There are a huge amount of animals that can be infected but mainly rodents. Mpox is caught from animal scratches and can now be passed from human to human through verticle transmission through the placenta, or horizontal transmission between individuals. The mpox reservoir is unknown.
