The invention of vaccines has dramatically reduced the incidence and mortality of related diseases, and it is estimated that about 6 million deaths could be avoided each year. The vaccine was first introduced in 1796 with the smallpox vaccine developed by Edward Jenner, which solved the previous problem of 30% mortality from smallpox. Since then, the vaccine industry has developed rapidly, and a variety of technologies have their own strengths. 1. Live/attenuated vaccines contain weakened forms of bacteria that only induce an immune response and do not cause disease. The first live vaccine was the smallpox vaccine.
Merit:
- No adjuvants are required;
- Generate cellular/humoral immunity;
- A single dose is sufficient to provide an immune response.
Shortcoming:
- There is a risk of toxic recovery;
- Immunocompromised patients are at risk of use;
- The storage conditions are strict and the storage time is short.
2. Inactivated vaccines use chemical/physical means to inactivate pathogens and make them incapacitated. The first inactivated vaccine was the cholera vaccine.
Merit:
- does not restore toxicity;
- cost reduction;
- Available in immunocompromised patients.
Shortcoming:
- Adjuvants are required;
- Need to use multiple doses;
- R&D is cumbersome, and pathogen culture requirements are high.
3. Subunit vaccines have antigen-specific pathogen fragments (such as proteins, peptides, sugars), which can be antigens that induce immune responses. The first subunit vaccine was the hepatitis B vaccine.
Merit:
- Does not contain intact pathogens, with high safety,
- There is less risk of side effects and does not cause a disease state;
- It can provide precise immune targets;
- It does not require refrigeration and is easy to transport and store.
Shortcoming:
- difficulty in isolating specific antigens;
- The immune response is weaker than that of traditional vaccines.
- Adjuvants are required to enhance efficacy.
Fourth, the toxoid comes from the toxin secreted by bacteria, and only the characteristics of inducing antibody formation are retained after being treated in a managerial way. The world's first toxoid vaccine was the diphtheria toxoid vaccine.
Merit:
- Security is high
- Stable and long-lasting;
- Not susceptible to temperature, humidity and light;
- There is no conversion case
Shortcoming:
- Boosters are needed to maintain the immune response;
- high cost of preparation;
- Adverse reactions are susceptible to the injection site
5. Polysaccharide-protein conjugate vaccine combines antigenic proteins and polysaccharides to form bacterial polysaccharide vaccines with protein as the carrier. The antigen surface area is increased and the immunogenicity of polysaccharides is improved. The first polysaccharide-protein conjugate vaccine was the Haemophilus influenzae type b (Hib) conjugate vaccine.
Merit:
- Immune memory can be formed;
- May prevent asymptomatic disease;
- Safe and well tolerated;
- Infants and young children have good immunization effects.
Shortcoming:
- The cost of preparation is high;
- Cannot target non-encapsulated variants;
- Difficult to target all bacterial serotypes.
6. Virus-like particle (VLP) vaccines are derived from the virus itself, which are self-assembled and formed by single or multiple structural proteins, which can mimic the size and conformation of the virus, and are very similar to the virus and easy to be recognized by the immune system. It does not contain viral genetic material and does not cause disease. The first VLP vaccine was the hepatitis B vaccine.
Merit:
- High safety, no viral genome, can prevent the potential pathogenicity of incomplete virus inactivation;
- No adjuvants are required;
- Induces a strong B-cell response;
- Diverse expression systems;
- High stability.
Shortcoming:
- High purification requirements;
- The preparation process is complex;
- high production costs;
- Stability deteriorates when conditions change.
7. Viral vector vaccines
It is prepared by using live attenuated virus as a vector and replacing some genes.
Merit:
- High gene transduction efficiency;
- High targeting;
- It can induce cellular and humoral immunity;
- Gene expression lasts for a long time.
Shortcoming:
- may induce an anti-vector immune response;
- An immune response against the vector may have been developed prior to vaccination;
- Large-scale production is difficult.
8. mRNA vaccines
The introduction of mRNA into the cell, which produces proteins, promotes an immune response that produces antibodies.
Winning the Nobel Prize in Physiology in 2023 is a very great contribution to the new crown, but it may hide some problems under the halo.
Merit:
- No conveyor system required;
- Short preparation time.
Shortcoming:
- Triggers inflammatory side effects;
- Stability may be poor;
(Recommended reading: mRNA) 9. DNA vaccines
Immunogen genes are inserted into plasmid formation, and the host cells receiving transfection express the protein and generate an immune response against that protein. At present, it is only in the experimental stage, and there is no finished product.
Merit:
- High stability;
- Easy to develop and produce;
- concentrated immune response;
- Durable immune response;
- Provides humoral and cellular immunity;
Shortcoming:
- Poor immunogenicity;
- elicits only an immune response against protein antigens;
- antibiotic resistance may occur;
- Anti-DNA antibodies may be produced, and there is a risk of autoimmune disease.
10. DC vaccine
It is a tumor vaccine, which extracts DCs from the body and is exposed to tumor peptides or tumor mRNA conditions, and then transplanted back into the body.
Merit:
- high immunogenicity;
- induce a high tumor immune response;
- Have immune memory.
Shortcoming:
- difficulty in target antigen selection;
- The production technology is complex and the cost is high.
(Recommended reading: A Brief History of DC Cell and DC Vaccine Research)
Resources
- https://www.sciencedirect.com/science/article/pii/B9780443185649000163
- Dubé E, Laberge C, Guay M, Bramadat P, Roy R, Bettinger J. Vaccine hesitancy: an overview. Hum Vaccin Immunother. 2013 Aug; 9(8):1763-73.
- Paterson P, Meurice F, Stanberry LR, Glismann S, Rosenthal SL, Larson HJ. Vaccine hesitancy and healthcare providers. Vaccine. 2016 Dec 20; 34(52):6700-6706.
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