Attenuated vaccine

Contents1. Definition

2. How it made

3. How it works

4. Advantages

5. Disadvantages

6. Examples

Attenuated vaccine derived from “wild,” or disease-causing, viruses or

bacteria that have been weakened under laboratory conditions.

Attenuated vaccine is strong enough to cause immune response, but too weak to cause disease

AVs stimulate an excellent immune response that is nearly as good as compared to an infection with the wild-type pathogen.

Viruses are often attenuated (weakened) by growing them in cells that they don’t normally grow in for many generations. The viruses begin to evolve and adapt to these new cells so that they are less able to live in their preferred environment.

Natural viruses need to reproduce thousands of times during infection to cause disease. These weakened viruses are only able to reproduce fewer than twenty times.

With such little reproduction, attenuated viruses are not able to create nearly enough copies of themselves to cause disease.

However, enough viral particles are created to create memory antibodies and keep the body from getting the viral infection should it enter the body naturally in the future.

How It made Preparation of LIVE but WEAKEN pathogens occur in

2 Steps:

Step 1Use the tissue culture to grow new viruses.

(Repeated Culture)

Step 2Fill the syringe with a strain of the virus that has desirable characteristics.

Step 1

You are about to create a live-attenuated vaccine, which means that you need to alter a pathogen so that it will still invade cells in the body and use those cells to make many copies of itself, just as would any other live virus.

The altered virus must be similar enough to the original virus to stimulate an immune response, but not so similar that it brings on the disease itself.

To create a new strain of the virus, you'll need to let it grow in a tissue culture.

The tissue culture is an artificial growth medium for the virus. You will intentionally make the environment of the culture different than that of the natural human environment. For this vaccine, you'll keep the culture at a lower temperature.

Step 2 Over time, the virus will evolve into strains that grow

better in the lower temperature. Strains that grow especially well in this cooler environment are selected and allowed to evolve into new strains.

These strains are more likely to have a difficult time growing in the warmer environment of the human body. After many generations, a strain is selected that grows slow enough in humans to allow the immune system to eliminate it before it spreads.

For example, the measles virus used as a vaccine today was isolated from a child with measles disease in 1954. Almost 10 years of serial passage using tissue culture media was required to transform the wild virus into attenuated vaccine virus.

The attenuation of virus to create live attenuated vaccines through reverse genetics technology, and introduce targeted mutations, represents the most advanced approach.

How it works A live attenuated vaccine contains a weakened form of

the infectious agent that cause the disease

The infectious agent is alive, so cause an infection, allowing the immune system to mount a complete defense

But the agent is attenuated, and doesn’t cause the host to become sick

the immune system produces T-lymphocytes and antibodies.

Once the imitation infection goes away, the body is left with a supply of “memory” T-lymphocytes, as well as B-lymphocytes that will remember how to fight that disease in the future.

the body takes a few weeks to produce T-lymphocytes and B-lymphocytes after vaccination.

Sometimes, after getting a vaccine, the imitation infection can cause minor symptoms, such as fever. Such minor symptoms are normal and should be expected as the body builds immunity.

To produce an immune response, live attenuated vaccines must replicate in the vaccinated person

Advantages A live attenuated vaccine is a method of delivering

weakened versions of a disease causing pathogen into the human body, where it can induce the immune system into preparing itself for any future encounters with the real.

Live vaccinations can usually immunize a person after a single dose, and regular boosters aren’t needed (as is the case with other types of vaccine). The MMR vaccine( is an vaccine is an excellent example of an effective live vaccine that only requires one or two doses to achieve its effects.

The MMR vaccine is an immunization vaccine against measles , mumps, and rubella.

It is estimated that 90% of the people receiving the MMR injection will become immunized after the first dose, and a second dose is provided by the NHS childhood immunization program to account for the remaining 10% of the population.

Live, attenuated vaccines can also sometimes be delivered by alternative routes. For example a polio vaccine( are used throughout the world to combat poliomyelitis) can be delivered orally, reducing the need for injections which many people might not be comfortable with.

Finally live, attenuated vaccines often result in fewer side effects than some alternative forms of vaccination like antibody vaccines.

Disadvantages

special storage

back mutation

side effects

special storage

Temperatures

time

Vaccine Storage

There are few immunization issues more important than the appropriate storage and handling of vaccines.

The success of efforts against vaccine-preventable diseases is attributable in part to proper storage and handling of vaccines.

Vaccines exposed to temperatures outside the recommended ranges can have reduced potency and protection.

Storage and handling errors can cost thousandsof dollars in wasted vaccine and revaccination.

Time Vaccines must be stored properly from the time they

are manufactured until they are administered.

Proper maintenance of vaccines during transport is known as the cold chain.

A proper cold chain is a temperature-controlledsupply chain that includes all equipment and procedures used in the transport and storage and handling of vaccines from the time of manufacturer to administration of the vaccine.

Temperatures Vaccines are fragile. • They must be maintained at the temperatures recommended by vaccine

manufacturers and protected from light at every link in the cold chain.

Most live virus vaccines tolerate freezing temperatures, but deteriorate rapidly after they are removed from storage.

Inactivated vaccines can be damaged by exposure to temperature fluctuations (e.g., extreme heat or freezing temperatures).

Potency can be adversely affected if vaccines are left out too long or exposed to multiple temperature excursions (out-of-range temperatures) that can have a cumulative negative effect.

It is a good idea to post a sign on the front of the storage unit(s) indicatingwhich vaccines should be stored in the freezer and whichshould be stored in the refrigerator.

Side-effects Some side-effects may be serious while others may

only be a mild inconvenience.

Everyone's reaction to a medicine is different

Measles Virus Live Attenuated/Mumps Virus Live Attenuated/Rubella Virus Live Attenuated (Measles, Mumps and Rubella vaccine (live) powder and solvent for solution for injection 0.5ml vials)

Very common: More than 1 in 10 people who have Measles virus live attenuated/Mumps virus live attenuated/Rubella virus live attenuated:

• fever injection site problems such as redness, swelling or pain Common: More than 1 in 100 people who have Measles virus live

attenuated/Mumps virus live attenuated/Rubella virus live attenuated:

• infections including respiratory tract infection

• skin rash or rashes

Uncommon: More than 1 in 1000 people who have Measles virus live attenuated/Mumps virus live attenuated/Rubella virus live attenuated

abnormal crying Bronchitis cough diarrhoea difficulty sleeping ear or hearing problems eye or eyesight problems feeling nervous loss of appetite swelling of the salivary glands vomiting

Rare: More than 1 in 10,000 people who have Measles virus live attenuated/Mumps virus live attenuated/Rubella virus live attenuated:

• convulsions

Very rare: Fewer than 1 in 10,000 people who have Measles virus live attenuated/Mumps virus live attenuated/Rubella virus live attenuated:

• brain or central nervous system problems

The frequency of these side-effects is unknown

• abnormal muscle movement

• arthritis

• joint pain

• thrombocytopenia

Mutation Mutation. This may lead to reversion to virulence (this is a major

disadvantage) One of the primary concerns for example, is the risk of reversion to a

more virulent strain of the virus or bacteria being vaccinated against. secondary mutation One or more of these will possess a mutation that enables it to infect

the new host. These mutations will spread, as the mutations allow the virus to grow

well in the new host; the result is a population that is significantly different from the initial population, and thus will not grow well in the original host when it is re-introduced (hence is "attenuated").

This makes it easier for the host's immune system to eliminate the agent and create the immunological memory cells which will likely protect the patient if they are infected with a similar version of the virus in "the wild".

Examples Measles virus

Mumps virus

Rubella virus

Polio virus

Yellow fever virus

Tuberculosis bacterium

(Chickenpox) vericella v.