Vaccination review

Vaccination is an idea to enhance the protective immunity In an organism by inoculating an antigen or substance.

The word vaccination is derived from a Latin word “vacca” meaning “cow”. Old females of Turkish nomads used to keep a needle (immersed in small pox lesion) with them. They used to use these needles to scratch the newborn. The newborn would develop a disease little bit but after some time newborn would recover and the newborn would had develop immunity against that disease.

In turkey British ambassador lord Montague’s son, who was living in England, was in those suffering from small pox disease as there was out break of small pox. He wrote a historical letter to Jenner to know about these happenings . Jenner observed the milkmaid hands and turkish action of needle . He took pus from cowpox lesion and developed the vaccine. Edward Jenner wanted to inject that vaccine in the son of Montague but he was strongly opposed by Queen and others. Jenner asked Montague for help and Montegue documented the permission letter. In which he said he himself will be responsible if any adverse effect of experiment will occur and sought permission from the queen for vaccination. After permission Jenner vaccinated the boy who after a mild ailment the boy recovered.  And thus he developed the vaccine against the smallpox disease. He termed this process as “variolation” (derived from “variola” smallpox) . Thus Edward Jenner is known as the father of vaccination.

Louis Pasteur worked on it and prepared many vaccines like Anthrax , Rabies and Fowl cholera and documented this work as vaccination. Pasteur named the current Vaccination from variolation. Pasteur later on established a company named “Pasteur Merieux” in France . it later on changed in “Rhone Poulenc” ( deals with human) and “Rhone Merieux” (dealing with animals). The company then converted into Sanofi Aventis.

Robert Koch and Pasteur belonged to rival countries. Koch worked on the disease and Pasteur worked on the prevention. This is the history of vaccination.

(Internet: Source)

Immunoprophylaxis against viral illnesses include the use of vaccines or antibody- containing preparations to provide immune protection against a specific disease.

Active immunization involves administrating a virus preparation that stimulates the body's immune system to produce its own specific immunity.

The principle of vaccination is to induce a "primed" state in the vaccinated subject so that following exposure to a pathogen, a secondary rapid immune response is generated leading to the accelerated elimination of the organism and protection from clinical disease.

Success depends on the generation of memory T and B cells and the presence in serum of neutralizing antibody.

Vaccines effectiveness is assessed in terms of percentage of recipients protected and the duration and degree of protection. Most effective viral vaccines protect more than 90% of recipients and produce fairly durable immunity.

Attributes of a good vaccine:

Live vaccines:

Following injection into the subject, the recombinant organism will replicate and express sufficient amounts of the foreign protein to induce a specific immune response to the protein.

Advantages of live vaccines:

Disadvantages of live vaccines:

Killed (inactivated) vaccines:

The organism is propagated in bulk, in vitro, and inactivated with either

β-propiolactone or formaldehyde.

These vaccines are not infectious and are therefore relatively safe, however they are usually of lower immunogenicity and multiple doses may be needed to induce immunity. In addition, they are usually expensive to prepare.

These vaccines are safe and fewer local reactions occur at the injection site, however it has the same disadvantages of poor immunogenicity and the need for multiple boosters applies.

The protein of interest may be extracted from lysates of the expression vector, then concentrated and purified for use as a vaccine. Example for this type of vaccine is the hepatitis B vaccine.

Advantages of killed vaccines:

Disadvantages of killed vaccines:

Immunogenicity may be enhanced by the incorporations of adjuvants into the vaccine preparation.

There are several possible modes of action for adjuvants:

DNA vaccines:

Are experimental at present, but have a promise future since they evoke both humoral and cell-mediated immunity, without the dangers associated with live virus vaccines.

The gene for an antigenic determinant of a pathogenic organism is inserted into a plasmid. This genetically engineered plasmid comprises the DNA vaccine which is then injected into the host.

Within the host cells, the foreign gene can be expressed (transcribed and translated) from the plasmid DNA, and if sufficient amounts of the foreign protein are produced, they will elicit an immune respone.

Passive immunization is the transfer of immunity to a host by means of immunoglobulins (preformed antibodies).

Immunoglobulins from immune individuals can be used as prophylaxis to prevent viral infections in exposed, but non-immune individuals.

It works by binding to extracellular virions and preventing them from attaching to and entering susceptible cells. The protective effect is short-lived (up to 3 months) because the antibodies are metabolized in the host.

For example Zoster immunoglobulin (prevention of Varicella in immunocompromised children and neonates) and Human Rabies immunoglobulin (post-exposure prophylaxis).

Passive immunity is also available in maternal milk, as it contains some antibodies from the mother which are transformed to the newborn. (Source: Internet notes)

Vaccines can be divided as

Vaccine that are prepared from one species and are used in that species. For example vaccine of cat is being vaccinated in cats.

The vaccines that are used intraspecies are known as hetero-vaccines. For example cowpox vaccine is being used in human.

Vaccines can also be divided as

            In case of live vaccines we introduce live antigen into the body. Live vaccines are mostly used in case of viruses(90%). Sometimes these are also used in case bacteria but very less e.g. in case of  anthrax and TB. Live vaccines have following benefits:

This include virus and bacteria

Anthrax: it may be

New castle disease virus (NDV): it may include:

Intermediate strain

Hot strain

An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable (or "live"). Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. Attenuation is done by changing the media

Attenuation is done by keeping in highly enrich media due to which it gradually loses it pathogenicity.

Rabies vaccine:

Rabies virus normally grows in mammals but for the attenuation we grow it in the egg. It looses its pathogenicity as media is changed.

Live vaccines are not preferred when:

An inactivated vaccine (or killed vaccine) is a vaccine consisting of virus particles, bacteria, or other pathogens that have been grown in culture and then killed using a method such as heat or formaldehyde.          

Following methods are used to inactivate the viruses:

Heat causes uncontrolled denaturation which is not needed so heat is no more used for inactivation.

UV light causes the mutation so that it is also not used.

Chemicals:

In chemical inactivation following chemicals are used:

Formaldehyde but it is not used in human.

Alum is also used.

In chemical inactivation controlled addition of the inactivants (chemicals) is done.

The route of administration is the path by which a vaccine (or drug) is brought into contact with the body.

The choice of route is of vital importance because incorrect route causes vaccine failure resulting in no immune response.

Live vaccines may be administered through the following routes:

Live vaccines are mostly used in flock management. In flock management spray is preferred which cover the above mentioned route. In this way no animal is skipped from vaccination. In this method signs, symptoms, and morality are not observed but the replication is going on in the body and morbidity also occur.

Rules for vaccination:

Vaccine that is orally used should be temperature tolerant. That is why vaccines are often kept in cooler or iceboxes such as vaccines against polio. Vaccines that are orally used are

Not much popular in human but frequently used in veterinary. For example it is used in herd, flock management. It is done with the help of spray.

Note:  In flock or herd management intraocular, intranasal and oral are used in combined way as these three parts are interconnected.

In case of poultry following vaccines are given by routes mentioned above:

These are given through

Water supply→ mixed in water tank and then delivered to the flock. For this purpose chicks are kept away from water to make them  thirsty  so that they could desire for water. Then the water in which vaccine is mixed is delivered to the flock.

spray→ in case of spray the size of droplet is under consideration.

In this route of vaccine a very minute amount of vaccine is required so  this route of vaccine is economic for vaccinator.

Vaccine of rabies and TB is done through this route. Vaccine is live enough to replicate and spread.

When vaccine contain oil (mineral oil & montanite oil) and formalin then this route is not used. Mostly killed vaccines are given through this route. For this route alum precipitate or aluminum gel is used. Following vaccines are done through this route:

Followings are the benefits of the

FMD & HS vaccines for long lasting effects can be given through this route.

In this route of vaccine is very low success rate. Modern vaccines like DNA, RNA, and recombinant vaccines are given through this route. It is vector based. Genome must be active and vector must be alive. Conventional vaccines are not done through this route.

It is also a modern and expensive method of vaccine. The success rate is very low also in this method.

For this method recombinant fruits and vegetables can be used. Super candy is another good example in this regard which is being tested for vaccination.

This is experimental method up-till now. Nano technology is being used in this method. The vaccine patch contain the Nano needles which contain vaccine. (micro injections)

Drop of water containing vaccine is enclosed inside a capsule which is made up of sea weed carbohydrate. This drop is being tested for vaccination.

Intra-cerebral:

           

Following are some common adjuvants:

v No adjuvant is used in live vaccine

Live vaccines are not injected. For example, polio vaccine in humans, ND vaccine in poultry

NEW CASTLE DISEASE (ND):

When live vaccines are given e.g ND vaccine in poultry, the virus will replicate in the sinuses. As a result, number of viruses will increase. The virus will get processed in crop, gizzard & then gets out of the body. The virus will replicate throughout the body of the bird. It will be attacked by MHC-1 & will activate T & B cells.

POLIO:

Polio virus is a GIT virus. It will replicate but does not cause disease.