Methods of acquiring immunity and Immunization

Prof Anura Weerasinghe

MD, FRCP(UK), DCH, DTM&H(London), PhD(Japan)

Professor of Physiology

Faculty of Medicine

Ragama

Objectives

• Methods of acquiring immunity

• Immunological basis for vaccination

• Schedule of EPI vaccination

• Non-EPI vaccines available in Sri Lanka

History of Immunization

Ancient times in India - Atharva Veda

Inoculation

A history of Medicine in Sri Lanka by C. G. Uragoda

A centenary publication Sri Lanka Medical Association

History of Immunization1796 - First vaccination by Edward Jenner

1802 - First vaccination in Sri Lanka

1886 - compulsory vaccinationH. White, The Ceylon manual, 1908

1900 - Bacteriological Institute, Colombo

1967 - Last definitive case in Sri Lanka1977 - Last endemic case in the world

- EPI/WHO1991 - Hepatitis B and yellow fever

Methods of acquiring immunity

Natural Artificial

Active Passive

Infection Utero Neonatal

Types of Artificial Immunity

Active Passive

Vaccines Immunoglobulins Antisera

Normal(IM) SpecificRabiesHepatitis BTetanusAnti-D

Immunological basis of

Immunization

Immunization policy

Immune response Epidemiology

logistics

Factors affecting the immune response

• Host– presence of maternal antibodies

– immune competence

• Vaccine– Type of vaccine

– mode of administration

– Interval between doses

– presence of other vaccines

Changes in maternal and neonatal IgG levels before and after birth

Factors affecting the immune response

• Host– presence of maternal antibodies

– immune competence

• Vaccine– Type of vaccine

– mode of administration

– Interval between doses

– presence of other vaccines

Types of vaccines• Live attenuated

– BCG, measles, OPV

• Killed– Pertussis, Japanese encephalitis

• Toxoids– Tetanus, Diphtheria

• Genetically engineered– Hepatitis B

Expanded Programme of Immunization; schedule in Sri Lanka

• BCG - At birth

• Hepatitis B – 2,4 & 6 months

• DPT & OPV - 2,4,6 & 18 months

• DT & OPV - School entry

• Measles - 9 months & 3 years (as MR)

• aTD & Rubella - 10 to 15 years

Vaccines in selected groups

• Japanese encephalitis– In endemic districts

• Yellow fever– Travelers to Africa and South America

Non-EPI vaccines • Hib vaccine

• MMR

• Varicella

• Typhoid

• Cholera

• Hepatitis A

• Meningococcal

• Pneumococcal

• Rabies

New Combined vaccines

• DPT+Hib

• DPT+Hep B

• Hepatitis A & B

• aTd

Adjuvants prolong the antigenic stimulusEg; oil in water

Objectives

• Methods of acquiring immunity

• Immunological basis for vaccination

• Schedule of EPI vaccination

• Non-EPI vaccines available in Sri Lanka

Contraindications to DPT• Severe adverse event to DPT

– anaphylaxis– collapse– encephalitis– non-febrile convulsion

• Evolving neurological disease– uncontrolled epilepsy– progressive encephalopathy

Immunization policy, WHO 1995

Allergy and vaccination• Anaphylactic raection following egg

ingestion – avoid vaccines prepared on hen’s egg

tissues (yellow fever & influenza)

Vaccine viruses propagated in chicken fibroblast cells (measles or MMR) can usually be given to such individuals.

Conditions which are not contraindications to

immunization• Minor illnesses such as upper RTI or diarrhoes with

fever <38.50C

• Allergy, asthma or other atopy

• Prematurity or small for dates

• Malnutrition

• Child being breastfed

• Family h/o convulsion

• Treatment with antibiotics, low dose steroid including topical and inhaled preparation

Conditions which are not contraindications to

immunization• Dermatoses, eczema or localized skin

infection

• Chronic diseases of heart, lung, kidney and liver

• Stable neurological condition, such as cerebral palsy and Down’s syndrome

• History of jaundice after birth

Immunization policy, WHO 1995

Contraindications to live vaccines

• SCID

• pregnancy

• AIDS

HIV is not a contraindication.

Future vaccines

• HIV

• malaria

• adult tuberculosis

• cancer

Discuss the immunological basis of the vaccinesin the EPI schedule.