Topic: Immunization, Baby friendly hospital, congenital cyanotic heart disease
Question: Give two examples for each of the following types of vaccines used in under-5 children: ① Capsular polysaccharide vaccines ② Conjugate vaccines ③ Recombinant vaccines Also, Define the following terms: ① Herd effect ② Vaccine efficacy
Reference Material-This material is informational alone and is not specifically prepared as an answer for any question. Readers may do their own research before finalising diagnoses according to the characteristics unique to each question. Readers should not proceed without cross-referencing with relevant textbooks as well as standard guidelines available.
Here are two examples for each type of vaccine used in children under 5 years of age:
1. Capsular polysaccharide vaccines: These contain purified capsular polysaccharides (long chains of sugar molecules) from the surface of bacteria. They are used for encapsulated bacteria like Streptococcus pneumoniae and Neisseria meningitidis. Examples are the pneumococcal polysaccharide vaccine (PPV23) and meningococcal polysaccharide vaccine (MPV4). They produce primarily B-cell dependent humoral immunity but weak T-cell response. They are not immunogenic in children under 2 years of age due to immaturity of their immune systems.
– Pneumococcal polysaccharide vaccine (PPV23)
– Meningococcal polysaccharide vaccine (MPV4)2.
2.Conjugate vaccines:These link the polysaccharide antigens to a protein carrier which helps to overcome the poor immunogenicity of polysaccharides in young children. The protein carrier stimulates the T-cells to produce a T-cell dependent response, enhancing the immune response to polysaccharides. Examples are Hib vaccine and PCV13. They induce stronger, long-lasting immunity in children under 2 years of age compared to polysaccharide alone.
– Haemophilus influenzae type b conjugate vaccine (Hib)
– Pneumococcal conjugate vaccine (PCV13)
3. Recombinant vaccines:These are produced by inserting DNA coding for viral or bacterial antigens into yeast or bacterial cells. They induce both humoral and cell-mediated immunity. Examples are the hepatitis B and rotavirus vaccines which are produced by recombinant DNA technology. They provide a high degree of protection against disease.
– Hepatitis B recombinant vaccine (Hep B)
– Rotavirus recombinant vaccine (Rotarix, Rotavac)
Definitions:
1. Herd effect: A reduction in the spread of infectious disease in an unimmunized population that occurs when a significant proportion of the population is immunized. Widespread immunization with effective vaccines leads to decreased circulation of the infectious agent in the whole community, including in individuals who have not been immunized.
This occurs when a high percentage of the population is immunized against an infectious agent, indirectly protecting those who are not immunized by reducing circulation of the agent. The unimmunized individuals are protected due to lack of exposure. The transmission of the infectious agent is inhibited by high population immunity. Vaccination of a high proportion of children can lead to virtual elimination of some diseases.
2. Vaccine efficacy: The ability of a vaccine to prevent disease or infection in a vaccinated group of people, under optimal conditions, in a clinical trial. It is calculated as (number of cases in unvaccinated group – number of cases in vaccinated group)/number of cases in unvaccinated group. It indicates how well a vaccine works in a controlled setting.
It is calculated in a controlled clinical trial and indicates how effective a vaccine is in an ideal setting. It is measured as the reduction in disease incidence in the vaccinated group compared to the unvaccinated control group. The higher the efficacy, the better the vaccine. Actual effectiveness may vary in real-world use due to factors like uptake rates. Efficacy provides an initial assessment of a vaccine which needs to be confirmed by effectiveness.
