MEDICINE FOR ALL

Protein-based subunit vaccines

Adverse reactions associated with subunit protein-based vaccines

• Acellular pertusis (aP)

1. Same as tetanus and diptheria toxoid vaccines
2. Acellular pertusus-containing vaccines are less reactogenic in terms of mild-to-moderate reactions than wP-containing vaccines

• Hepatitis B (HepB)

1. Very rare
2. Reports of severe anaphylactic reactions are very rare

Protein-based subunit vaccines

Commonly used protein-based subunit vaccines are the following:

• Acellular pertusis (aP) vaccines contain inactivated pertussis toxin (protein) and may contain one or more other bacterial components. The pertusis toxin is detoxified either by treatment with a chemical or by using molecular genetic techniques
• Hepatitis B vaccines are composed of the hepatitis B virus virus surface antigen (HBsAg), a protein produced by hepatitis B virus. Earlier vaccine products were produced using purified plasma of infected individuals. This production method has been replaced by recombinant technology that can produce HBsAg without requiring human plasma increasing the safety of the vaccine by excluding the risk from potential contamination of human plasma.

Protein-based subunit vaccines

Protein based subunit vaccines present an antigen to the immune system without viral particles, using a specific, isolated protein of the pathogen. A weakness of this technique is that isolated proteins, if denatured, may bind to different antibodies than the protein of the pathogen.

Subunit vaccines

Subunit vaccines can be further categorized into:

• Protein -based subunit vaccines
• Polysaccharide vaccines
• Conjugate subunit vaccines

Subunit vaccines:

Safety and stability

Like inactivated vaccines, subunit vaccines do not contain live components and are considered as very safe.

Immune response:

• Must determine which combination of antigenic properties will produce an effective immune response with the correct pathway
• A response may be elicited, but with no guarantee that memory will form for future responses
• Less strong immune response compared to LAVs

Safety and stability:

• Have no live components, no risk of inducing the disease
• Safer and more stable than LAVs
• Excellent stability profile

Subunit vaccines

Immune response:

• 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. These parts are necessary to elicit a protective immune response
• This precision comes at a cost, as antigenic properties of the various potential subunits of a pathogen must be examined in detail to determine which particular combinations will produce an effective immune response witthin the correct pathway
• Often a response can be elicited, but there is no guarantee that immunological memory will be formed in the correct manner

Inactivated whole-cell vaccines

Safety and stability:

• Inactivated whole-cell vaccine have no risk of inducing the disease they are given against as they do not contain live components
• They are considered more stable than LAV vaccines.

Inactivated whole-cell vaccinations

Immune response:

• Inactivated-whole cell vaccines may not always induce an immune response and the response may not be long lived
• Several doses of inactivated whole-cell vaccines may be required to evoke a sufficient immune response

Inactivated whole-cell vaccinations

Inactivated vaccines are made from microorganism (viruses, bacteria, other) that have been killed through physical or chemical process. These killed organisms cannot cause disease.

Yellow fever (YF):

1. Hypersensitivity reactions

• Very rare
• Sensitivity to egg, which is commonly used to stabilize the vaccine, may explain at least some of these cases

2. Vaccine-associated neurotropic disease (encephalitis)

• Very rare
• Infants seem more susceptible to vaccine-associated neurotropic disease than the YF-vaccinated population at large

3. Vaccine-associated viscerotropic disease

• Very rare in children at 0.00001%
• The elderly seem more susceptible to reactions (very rare at 0.04-0.05%) than the YF-vaccinated population at large