Vaccinations - Basics

DR.PADMESH. VPEDIATRICIAN,AWACH.

A little flashback...

HISTORY OF VACCINATION:

429 BC

Greek historian Thucydides noticed that people who survive smallpox did not get re-infected.


900 AD

Chinese discover variolation

Primitive form of vaccination

Aim was to prevent smallpox by exposing healthy people to tissue from the scabs of infected people.


1796 AD

Edward Jenner discovers vaccination

“The father of immunology“.

His work is said to have "saved more lives than the work of any other human"


1796 AD

Noting that milkmaids who suffered the mild cowpox never contracted smallpox, Jenner experimented on several children, including his own 11-month-old son.

He inserted pus taken from pustule of Cowpox and inserted it into an incision on childrens’ arm. Later injected variolous material, but those children did not get infected with small pox.


1798 AD

The results were finally published and Jenner coined the word Vaccine from the Latin 'vacca' for cow.


1803 AD

Royal Jennerian Institute founded


1880 AD

Rabies Vaccine developed by Louis Pasteur


1890 AD

German scientist Emil von Behring discovered the basis of diphtheria and tetanus vaccines.

Awarded the first Nobel Prize in Physiology/ Medicine.


1920 AD

Vaccines available against TB, diphtheria, tetanus, pertussis.


1980 AD

Small pox eradicated from the world.

immunity

IMMUNITY

INNATE ACQUIRED

(GENETIC)

IMMUNITY

IMMUNITY

VACCINES

VACCINE (antigenic material)

Pathogens

A vaccine typically contains an agent that resembles a disease-causing agent.

It is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins.

The vaccine stimulates the body's immune system to recognize the agent as a threat, destroy it, and keep a record of it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.

By priming the immune system by vaccination, when the vaccinated individual is later exposed to the live pathogens in the environment, the immune system can destroy them before they can cause disease.

Vaccines are of 4 types:

(i) Live attenuated vaccines: consist of live bacteria

or viruses which have been rendered avirulent.

(ii) Killed (Inactivated) vaccines: consist of microorganisms killed by heat or chemicals.

(iii) Subunit vaccines: only the antigens that best stimulate the immune system are included

(iv) Toxoids: are modified bacterial exotoxins so

that toxicity is lost but antigenicity is retained.

(i) Live attenuated vaccines:

(i) Live attenuated vaccines: ADVANTAGES:

Excellent immune response that is nearly as good a wild infection.

Live microorganisms provide continual antigenic stimulation giving sufficient time for memory cell production.

Attenuated pathogens are capable of replicating within host cells Cell mediated immunity possible.

(i) Live attenuated vaccines: DISADVANTAGES:

Can revert to original form and can cause disease.

Harmful to immunocompromised patients.

Not given in pregnancy.

Less stable, most require strict cold chain.

(i) Live attenuated vaccines: DISADVANTAGES:

Can revert to original form and can cause disease.

(i) Live attenuated vaccines: EXAMPLES.

Varicella

BCG

Rota virus

OPV

MMR

(i) Live attenuated vaccines: EXAMPLES.

Varicella

BCG

Rota virus

OPV

MMR

(ii) Inactivated (Killed) vaccines:

(ii) Inactivated (Killed) vaccines: ADVANTAGES:

No live component So will never cause disease.

Safer than Live vaccines

More stable than Live vaccines.

(ii) Inactivated (Killed) vaccines: DISADVANTAGES:

May not always induce an immune response after the 1st dose.

Immune response may not be long lived.

Several doses of inactivated vaccines may be required to evoke a sufficient immune response.

(ii) Inactivated (Killed) vaccines: EXAMPLES:

Whole Cell Pertussis.

Inactivated Polio

(iii) Sub unit Vaccines:


Subunit vaccines, like inactivated whole-cell vaccines, do not contain live components of the pathogen.

They differ from inactivated whole-cell vaccines, by containing only the antigenic parts of the pathogen.

(iii) Sub unit Vaccines: ADVANTAGES:

No live components Hence cannot cause disease

Safer than Live vaccines

More stable than Live vaccines.

(iii) Sub unit Vaccines: DISADVANTAGES:

No guarantee that immunological memory will be formed in the correct manner.

Less immune response compared to Live vaccines.


3 types:

1.Protein based

2. Polysaccharide

3. Conjugate


1.Protein based Vaccine

A specific isolated protein of the pathogen is used.

Disadvantage: If that protein is denatured, immune response may be inadequate.

Eg: Acellular Pertussis (inactivated pertussis toxin

+ bacterial components)

Hepatitis B vaccine ( Hepatitis B surface Antigen HBsAg )


2.Polysaccharide Vaccine

Polysaccharide from cell wall of bacteria is used.

Disadvantage:

-T-cell independent (Stimulate B cells without stimulating T Helper cells)

Poor immune response in < 2 years age

Only Short term immunity (No immune memory)

No booster response even after repeated injections


2.Polysaccharide Vaccine

Examples:

- Typhoid Vi Polysaccharide Vaccine

- Pneumococcal Polysaccharide vaccine


3. Conjugate Vaccine:

Polysaccharide from cell wall of bacteria is used

+

CARRIER PROTEIN

( Conjugation )

T Cell Independent T Cell DEPENDENT immunity

1. Increased Immune response <2years age

2. Booster response to multiple doses


3. Conjugate Vaccine:

Examples:

- Hib

- Pneumococcal Conjugate Vaccines (PCV-10,13)

(iv) Toxoid Vaccines:

(iv) Toxoid vaccines: Toxin is rendered harmless and used as the antigen in

the vaccine to elicit immunity.

ADVANTAGES:

Does not cause disease.

DISADVANTAGES:

Not highly immunogenic

May require multiple doses

(iv) Toxoid vaccines:

Examples:

- Tetanus Toxoid

- Diphtheria Toxoid

FAQs

Question 1:

I am scared about side effects of vaccine after media reports.

Answer:

Serious side effects are extremely rare, and mostly due to human error, rather than vaccine itself.

Question 2:

My Child was immunised against this disease, yet she got it. Why?

No vaccine provides 100% protection.

The incidence is decreased drastically, and even if

the child gets the disease, it will be mild.

Question 3:

My Child has so many pending vaccinations. Can they be given 1 week apart, so as to finish them early?

No.

Any number of vaccines can be given on the same day.

However,if not given on the same day, a minimum of 28 days interval should be maintained before the next vaccination.

Question 4:

I missed giving my child a vaccine at the recommended date. Should I start over all again?

No.

Immune system has good memory function.

So no need to re-start schedule. Continue from

where you left it.

Question 5:

When I went to one pediatrician, I was told one schedule. When I went to another doctor, I was given another schedule. Which is the correct one?

There are many schedules- National Immunization Program, WHO program, and

IAP Recommendations.

Stick on to one schedule.

Also, recommendations keep changing.

Question 6:

Should I give the optional vaccines? Especially the expensive ones?

All optional vaccines should be given if affordable.

They are effective.

Question 7:

What is ‘Painless vaccine’? Is it less effective than the normal vaccine?

DTaP is called the Painless vaccine.

Though efficacy is said to be almost the same, the current recommendation is to use DPT, and not DTaP.

Question 8:

What vaccine should be taken for Polio? OPV or IPV?

IPV is the current recommendation. However, if IPV is not feasible, OPV can be given.

6,10,14 weeks IPV

6 mth, 9 mth, 5 years OPV

Question 9:

What is the schedule for Chicken pox vaccine?

The current recommendation for Varicella is:

After 15 months of age 1st Dose

At 5 years 2nd Dose

(2nd dose can be given anytime 3 months after 1st

dose)

Question 10:

What is the recommendation regarding pneumococcal vaccine?

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Health & Medicine

Vaccinations - Basics