PU520: Principles of Epidemiology Unit 8 Vaccines and Vaccine-Preventable Diseases Flashcards
What are a critical tool in public health and infection prevention, primarily as a primary prevention strategy?
Vaccines
How do vaccines work?
By causing an individual’s system to develop antibodies to either a weakened or dead form of the pathogen. Antibodies are disease specific.
What are the two forms of immunity?
Active and passive
When does active immunity occur?
When the individual is exposed to a pathogen, which triggers the immune system to produce antibodies to that disease.
This type of exposure can occur through infection with the actual disease (which results in natural immunity) or through intentional exposure to a weakened form of the pathogen through vaccination (which results in vaccine-induced immunity). Active immunity, whether naturally occurring or vaccine induced, is long lasting.
What stores the information of the pathogen and where do they reside and how long?
Memory B cells, they circulate in the blood and reside in the bone marrow for a long time, if not a lifetime.
Vaccines simulate natural infection and produce a similar immune response, including memory B cells.
When does passive immunity occur?
How long does it last?
Passive immunity occurs when an individual is given antibodies to a disease, rather than producing them through their own immune system. Neonates have passive immunity from antibodies passed from the mother through the placenta. Passive immunity can also be given by administration of antibody-containing blood products, such as red blood cells, plasma products, and immune globulin.
A third major source of passive immunity is heterologous hyperimmune serum, or antitoxin. It is available for botulism and diphtheria but it carries a risk of inducing an immune reaction to the horse protein, known as serum sickness.
Passive immunity only lasts from a few weeks or months, but the protection is immediate. While active immunity lasts longer, it may take up to several weeks to develop.
What are the different types of vaccines? (4)
- Use of weakened, but live, viruses to generate immunity.
- Inactivated or killed viruses
- Inactivated toxins (for bacterial illness where toxins generated by the bacteria are the cause of illness)
- Segments of the virus (subunit or conjugate vaccines)
What are examples of live, attenuated vaccines?
Measles, mumps, and rubella (MMR).
Polio vaccine was one as well called OPV or oral polio vaccine. However, it would undergo mutations which was common, so it is no longer used. Now IPV, an inactivated version on the childhood immunization schedule, is used in response. OPV is no longer recommended.
How are live, attenuated vaccines created?
A common method to create attenuated vaccine is to grow the virus in a series of chick embryos. With each pass through the chick embryo, the virus adapts at replicating in chick cells, but less able to replicate in human cells. Eventually, the virus will not be able to replicate in human cells at all but the virus will still be recognized by the human immune system. When this weakened virus is given to a human, it cannot replicate to produce illness but can stimulate an immune response that can provide for protection against future infection.
T/F Live, attenuated vaccines are fragile to heat and light AND typically provide longer protection than the inactivated version.
True
How are killed or inactivated vaccines created?
Killed, or inactivated, vaccines are created by inactivating the pathogen with heat or chemicals (e.g., formaldehyde or formalin). The heat or chemical treatment destroys the pathogen’s ability to replicate, but the virus is still intact and recognizable by the human’s immune system.
What is the benefit of inactivated vaccines?
The benefit of inactivated vaccines is that there is not a risk that they will mutate back to a form that can replicate; however, the immunity provided by these vaccines tends to be shorter acting.
The Centers for Disease Control and Prevention (CDC) says “Inactivated vaccines always require multiple doses.”2(p6) The IPV and the injectable form of the influenza vaccine (IIV) are examples of inactivated vaccines in the recommended childhood immunization schedule.
How are toxoid (antitoxin) vaccines created?
Remember: these are created in response to bacteria that release toxic chemicals that cause disease within the body rather than the presence of the disease itself.
For these type of illnesses, an immunization is made by inactivating the toxin by heat or chemical processing, or other methods.3(p2) This type of immunization is called a “toxoid” and is sometimes included under
the category of inactivated/killed vaccines.
Examples of toxoids included in the United States recommended childhood immunization schedule are the tetanus and diphtheria immunizations, which are offered in a combined form.
What is a subunit vaccine? Give one example.
What is a recombinant vaccine? Give one example.
Other vaccines, such as subunit and conjugate vaccines, only contain pieces of the virus or bacteria that they protect against. Subunit vaccines include only a portion of the pathogen, enough to elicit a response from the human immune system, but not large enough to cause illness. One method of manufacturing subunit vaccines is to isolate a protein from the pathogen and use it as the main antigen.
The acellular pertussis and some versions of the influenza vaccine are made this way.
Another type of subunit vaccines, called recombinant vaccines, can be made through genetic engineering—a gene coding for a vaccine protein (of the target pathogen) is inserted into another virus or into producer cells in culture. The vaccine protein is created when the carrier cell reproduces or when the producer cell metabolizes. When this type of vaccine is given, the immune system will recognize the protein of the target pathogen.
Currently, the only type of recombinant vaccine licensed for use in the United States is the hepatitis B vaccine. HPV as well.
What is a polysaccharide vaccine?
Polysaccharide vaccines are a type of subunit vaccine that contains a portion of the surface capsule (or coating) of certain bacteria. The long chains of sugar molecules that compose the bacterial coating are used to elicit an immune response.
According to the CDC, Pure polysaccharide vaccines are available for three diseases: pneumococcal disease, meningococcal disease, and Salmonella typhi.
In addition to handling and storage of vaccines, what should facilities and organizations that provide vaccines should implement?
Vaccine management that is in charge of ordering, managing inventory, and monitoring storage conditions.
There should also be an emergency vaccine retrieval and storage plan for times in which the cold chain might be endangered, such as refrigerator or freezer malfunctions, power failures, or natural disasters.
