Immunoprophylaxis involves using vaccines or antibodies to prevent infections before exposure. It strengthens immune defenses, reduces disease transmission, and supports public health—essential in nursing, microbiology, and global immunization programs.
Introduction
Immunoprophylaxis refers to the prevention of infectious diseases by inducing immunity, either actively through vaccination or passively via administration of preformed antibodies. This preventive strategy forms the cornerstone of public health efforts worldwide, significantly reducing morbidity and mortality associated with infectious diseases.
Vaccination
Mechanism of Vaccination
Vaccination is a process that stimulates the immune system to develop adaptive immunity against specific pathogens. It involves the administration of antigenic material (such as killed or live attenuated microorganisms, or components thereof) that mimics infection, prompting the body to produce protective antibodies and memory cells. This immunological memory enables rapid and effective responses upon subsequent exposure to the same pathogen, thereby preventing disease or reducing its severity.
Historical Perspective
The history of vaccination dates back to the late 18th century with Edward Jenner’s pioneering work on smallpox. Jenner’s use of cowpox to confer protection against smallpox laid the foundation for modern vaccines. Over the centuries, advances in microbiology, immunology, and biotechnology have expanded the scope of vaccination to include numerous bacterial and viral diseases. Notable milestones include the development of the polio vaccine by Jonas Salk and Albert Sabin, and the introduction of the measles, mumps, and rubella (MMR) vaccine.
Role in Disease Prevention
Vaccines have dramatically decreased the incidence of vaccine-preventable diseases (VPDs). Widespread immunisation has led to the eradication of smallpox, near-elimination of polio, and significant reductions in diseases such as diphtheria, pertussis, and tetanus. In addition to direct protection, vaccination contributes to herd immunity, protecting vulnerable populations who cannot be immunised due to age, medical conditions, or other factors. The success of immunisation programmes hinges on high coverage rates, effective vaccine delivery, and robust surveillance systems.
Examples of Commonly Used Vaccines
| Vaccine Name | Target Disease(s) | Vaccine Type | Recommended Age Group |
| BCG | Tuberculosis | Live attenuated | Neonates (at birth) |
| Oral Polio Vaccine (OPV) | Poliomyelitis | Live attenuated | Infants and children |
| Inactivated Polio Vaccine (IPV) | Poliomyelitis | Killed/inactivated | Infants and children |
| DPT | Diphtheria, Pertussis, Tetanus | Killed/inactivated (pertussis), toxoid (diphtheria, tetanus) | Infants and children |
| Hepatitis B Vaccine | Hepatitis B | Subunit (recombinant DNA) | Infants, children, adults |
| Measles Vaccine | Measles | Live attenuated | Infants, children |
| MMR (Measles, Mumps, Rubella) | Measles, Mumps, Rubella | Live attenuated | Children |
| Rotavirus Vaccine | Rotavirus diarrhoea | Live attenuated | Infants |
| Pneumococcal Vaccine | Streptococcus pneumoniae infections | Conjugate (PCV), polysaccharide | Infants, children, elderly |
| Human Papillomavirus (HPV) Vaccine | Cervical cancer, HPV infection | Subunit (virus-like particles) | Adolescents, young adults |
| Influenza Vaccine | Seasonal influenza | Killed/inactivated, live attenuated (nasal) | All age groups (with emphasis on high-risk groups) |
| Rabies Vaccine | Rabies | Killed/inactivated | Post-exposure, high-risk individuals |
Characteristics of Killed and Live Vaccines
| Feature | Killed (Inactivated) Vaccines | Live Attenuated Vaccines |
| Composition | Whole organisms killed by heat/chemicals or subunits | Live microorganisms attenuated to reduce virulence |
| Examples | IPV, Hepatitis A, Rabies, Influenza (injected), DPT (pertussis component) | BCG, OPV, MMR, Measles, Rotavirus, Yellow fever |
| Immune Response | Mainly humoral; weaker cellular immunity | Strong humoral and cellular immunity |
| Number of Doses | Multiple doses/boosters often required | Usually single or few doses |
| Duration of Immunity | Generally shorter; requires boosters | Long-lasting, sometimes lifelong |
| Safety | Safe in immunocompromised individuals | Contraindicated in immunocompromised, pregnant women |
| Storage | Less stringent requirements | Requires cold chain; sensitive to temperature |
| Adverse Events | Mild local reactions common | Occasional mild infection; rarely severe |
| Advantages | Safe, stable, suitable for mass immunisation | Strong immunity, fewer doses |
| Disadvantages | Weaker immunity, frequent boosters, less effective in some populations | Risk of reversion to virulence, contraindicated in some groups |
Passive Immunoprophylaxis
Definition
Passive immunoprophylaxis involves the administration of preformed antibodies to confer immediate protection against specific pathogens. Unlike active immunisation, it does not stimulate the recipient’s immune system to produce its own antibodies, and thus provides temporary immunity.
Types of Passive Immunoprophylaxis
- Natural Passive Immunity: Transfer of maternal antibodies (mainly IgG) across the placenta to the foetus, and via breast milk (IgA) to infants.
- Artificial Passive Immunity: Administration of immunoglobulins or antisera derived from humans or animals, used for prophylaxis or treatment of specific infections.
Indications
- Post-exposure prophylaxis (e.g., rabies, tetanus, hepatitis B)
- Protection in immunocompromised individuals
- Prevention of disease in high-risk situations (e.g., after needle-stick injury, newborns of hepatitis B carrier mothers)
- Treatment of certain infections or toxin-mediated diseases (e.g., diphtheria, botulism)
Examples of Passive Immunoprophylaxis
- Rabies Immunoglobulin: Administered along with rabies vaccine for post-exposure prophylaxis.
- Tetanus Immunoglobulin: Used in non-immunised or incompletely immunised individuals with tetanus-prone wounds.
- Hepatitis B Immunoglobulin (HBIG): Given to neonates born to hepatitis B-positive mothers and post-exposure cases.
- Varicella Zoster Immunoglobulin: Used in susceptible individuals exposed to chickenpox.
- Antitoxins: Diphtheria and botulinum antitoxins for treatment of respective diseases.
Passive immunoprophylaxis provides rapid protection, but its effects are short-lived (weeks to months), and it does not induce immunological memory.
WHO Immunization Schedule
Overview and Rationale
The World Health Organization (WHO) recommends a global immunisation schedule designed to maximise protection against major infectious diseases, especially in childhood. The schedule is periodically updated based on epidemiological trends, vaccine efficacy, safety data, and local considerations. The rationale behind the schedule is to provide timely and effective protection, reduce disease burden, and establish herd immunity.
WHO-Recommended Childhood Immunization Schedule (2025)
| Age | Vaccine(s) | Disease(s) Prevented | Type |
| At birth | BCG, Hepatitis B (first dose), OPV (zero dose) | Tuberculosis, Hepatitis B, Poliomyelitis | Live (BCG, OPV), Subunit (Hep B) |
| 6 weeks | DPT (first dose), OPV (first dose), Hepatitis B (second dose), Hib, Rotavirus, PCV | Diphtheria, Pertussis, Tetanus, Poliomyelitis, Hepatitis B, Haemophilus influenzae type b, Rotavirus diarrhoea, Pneumococcal diseases | Killed (DPT, Hib), Live (OPV, Rotavirus), Subunit (Hep B), Conjugate (PCV) |
| 10 weeks | DPT (second dose), OPV (second dose), Hib, Rotavirus, PCV | As above | As above |
| 14 weeks | DPT (third dose), OPV (third dose), Hib, Rotavirus, PCV | As above | As above |
| 6–9 months | Measles (first dose) | Measles | Live attenuated |
| 9–12 months | Yellow fever (in endemic areas), MMR | Yellow fever, Measles, Mumps, Rubella | Live attenuated |
| 12–18 months | DPT booster, OPV booster, Hib booster, Hepatitis A, MMR (second dose), Chickenpox | As above plus Hepatitis A, Varicella | Killed (Hep A), Live (MMR, Chickenpox) |
| 2 years | Typhoid conjugate vaccine | Typhoid fever | Conjugate |
| 4–6 years | DPT booster, OPV booster, MMR booster | As above | As above |
| 10–12 years | HPV vaccine (girls) | Human papillomavirus infection, Cervical cancer | Subunit |
The schedule may be tailored to national needs, availability of vaccines, and epidemiological considerations. In India, the Universal Immunisation Programme (UIP) closely aligns with the WHO recommendations, with additional provisions for region-specific diseases.
Recommended Ages and Vaccine Types
- Vaccines are administered at specific ages to coincide with periods of increased susceptibility and optimal immune response.
- Live vaccines are generally given earlier, except in cases where maternal antibodies may interfere with efficacy.
- Killed and subunit vaccines are used where safety is paramount, especially in immunocompromised populations.
- Booster doses are scheduled to maintain immunity over time.
Special Considerations
- Catch-up immunisation is recommended for children who miss scheduled doses.
- Additional vaccines (e.g., Japanese encephalitis, cholera, meningococcal, COVID-19) may be included based on local epidemiology.
- Adverse events following immunisation (AEFI) should be reported and managed promptly.
- Cold chain maintenance is critical for vaccine efficacy.
Conclusion
Immunoprophylaxis, through vaccination and passive immunisation, remains a vital component of modern healthcare. Vaccines have revolutionised disease prevention, saving countless lives and improving quality of life. The distinction between killed and live vaccines guides their appropriate use, while passive immunoprophylaxis offers rapid protection in specific scenarios. Adherence to the WHO immunisation schedule ensures timely and comprehensive coverage against major infectious diseases.
Looking ahead, ongoing research aims to develop new vaccines for emerging pathogens, improve vaccine safety and efficacy, and expand coverage to underserved populations. Innovations such as mRNA vaccines, improved delivery systems, and global cooperation promise to further strengthen immunoprophylaxis as a pillar of public health. For medical students and healthcare professionals, a thorough understanding of immunoprophylaxis principles and practices is essential for effective disease prevention and health promotion.
REFERENCES
- Apurba S Sastry, Essential Applied Microbiology for Nurses including Infection Control and Safety, First Edition 2022, Jaypee Publishers, ISBN: 978-9354659386
- Joanne Willey, Prescott’s Microbiology, 11th Edition, 2019, Innox Publishers, ASIN- B0FM8CVYL4.
- Anju Dhir, Textbook of Applied Microbiology including Infection Control and Safety, 2nd Edition, December 2022, CBS Publishers and Distributors, ISBN: 978-9390619450
- Gerard J. Tortora, Microbiology: An Introduction 13th Edition, 2019, Published by Pearson, ISBN: 978-0134688640
- Durrant RJ, Doig AK, Buxton RL, Fenn JP. Microbiology Education in Nursing Practice. J Microbiol Biol Educ. 2017 Sep 1;18(2):18.2.43. https://pmc.ncbi.nlm.nih.gov/articles/PMC5577971/
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