Types of Vaccines
Vaccines help the immune system recognize a disease and respond to it quickly. The classification of vaccines depends on which part of the pathogen is used in their production.
Vaccines can be divided into two main types: live attenuated vaccines and non-live vaccines. Live attenuated vaccines contain weakened but viable pathogens that can reproduce to a limited extent in the body and induce a strong and long-lasting immune response. Non-live vaccines, on the other hand, are based on inactivated microorganisms, their parts or genetic material and are unable to reproduce in the body.
Live attenuated vaccines contain weakened live microorganisms that retain the ability to reproduce in the body, but are weakened and generally do not cause disease in healthy people. Examples include BCG, rotavirus, MMR, chickenpox and yellow fever vaccines.
Non-replicating or non-live vaccines do not contain microorganisms capable of reproduction. This group includes, for example:
- inactivated vaccines, which contain the pathogen that has been rendered incapable of reproduction;
- component vaccines, which contain only specific antigens of the pathogen or the genetic material necessary for their production.
Component vaccines include, for example, alloantibody, polysaccharide, conjugated polysaccharide, toxoid and recombinant vaccines. Nucleic acid-based vaccines, such as mRNA vaccines, are also used today.
Attenuated live vaccines
Attenuated live vaccines contain a live but weakened pathogen that does not cause disease in healthy people. The virus or bacterium in the vaccine is able to multiply in the body but has lost its ability to cause disease.
After the vaccine is administered, an immune response is triggered in the human body that is similar to recovering from a natural infection. This results in the development of strong and long-lasting immune memory.
Attenuated live vaccines contain a live but weakened pathogen that does not cause disease in healthy people. The virus or bacterium in the vaccine is able to multiply in the body but has lost its ability to cause disease.
After the vaccine is administered, an immune response is triggered in the human body that is similar to recovering from a natural infection. This results in the development of strong and long-lasting immune memory.
Since attenuated live vaccine viruses or bacteria remain active in the immune system for a long time, a large number of memory cells are formed in the body. Consequently, immune memory is long-lasting and strong.
Attenuated live vaccines typically provide good protection with just one dose; in rare cases, two doses are needed to establish immunity.
Since attenuated live vaccine viruses or bacteria remain active in the immune system for a long time, a large number of memory cells are formed in the body. Consequently, immune memory is long-lasting and strong.
Attenuated live vaccines typically provide good protection with just one dose; in rare cases, two doses are needed to establish immunity.
Disadvantages of attenuated live vaccines
They are very sensitive and fragile. Live vaccines are sensitive to temperature and light and may degrade under improper storage conditions. Therefore, cold chain requirements must be strictly followed.
Theoretically, it is possible that the live virus contained in the vaccine could regain its disease-causing properties. This has occurred only with the attenuated live polio vaccine, at a rate of approximately one case per 2.4 million vaccinated individuals.
They are not typically administered to pregnant women.
They are very sensitive and fragile. Live vaccines are sensitive to temperature and light and may degrade under improper storage conditions. Therefore, cold chain requirements must be strictly followed.
Theoretically, it is possible that the live virus contained in the vaccine could regain its disease-causing properties. This has occurred only with the attenuated live polio vaccine, at a rate of approximately one case per 2.4 million vaccinated individuals.
They are not typically administered to pregnant women.
Not suitable for individuals with immunodeficiency. In people with severe immunodeficiency, the vaccine virus or bacterium may multiply excessively in the body, so these vaccines are not administered to them.
May be less effective after a blood or blood product transfusion. If a person has developed temporary passive immunity through donor blood or blood products, the immune response to a live vaccine may be weak or absent. The measles vaccine is most susceptible to this, while the poliomyelitis and rotavirus vaccines are less susceptible.
Not suitable for individuals with immunodeficiency. In people with severe immunodeficiency, the vaccine virus or bacterium may multiply excessively in the body, so these vaccines are not administered to them.
May be less effective after a blood or blood product transfusion. If a person has developed temporary passive immunity through donor blood or blood products, the immune response to a live vaccine may be weak or absent. The measles vaccine is most susceptible to this, while the poliomyelitis and rotavirus vaccines are less susceptible.
Inactivated vaccines
Inactivated vaccines are made from pathogens that are grown in tissue cultures or on media and are then inactivated through heat or chemical treatment.
The viruses or bacteria contained in inactivated vaccines do not replicate, making them safe even for people with immunodeficiency. The effectiveness of these vaccines is not affected by antibodies circulating in the blood, such as those from previously administered donor blood or blood products, immunoglobulins, transplants, etc.
Inactivated vaccines are made from pathogens that are grown in tissue cultures or on media and are then inactivated through heat or chemical treatment.
The viruses or bacteria contained in inactivated vaccines do not replicate, making them safe even for people with immunodeficiency. The effectiveness of these vaccines is not affected by antibodies circulating in the blood, such as those from previously administered donor blood or blood products, immunoglobulins, transplants, etc.
Inactivated vaccines have lower immunogenicity than attenuated live vaccines. Protective immunity may not develop after the first vaccine dose, so multiple doses are required to achieve lasting protection.
Over time, immunity levels may decline, so inactivated vaccines must be administered repeatedly to maintain protection against disease.
Inactivated vaccines have lower immunogenicity than attenuated live vaccines. Protective immunity may not develop after the first vaccine dose, so multiple doses are required to achieve lasting protection.
Over time, immunity levels may decline, so inactivated vaccines must be administered repeatedly to maintain protection against disease.
Subunit vaccines
Subunit, or fractional, vaccines are inactivated vaccines. They do not contain viable pathogens and are safe. Unlike inactivated whole-cell vaccines, they contain only specific parts or fragments of the pathogen.
Subunit, or fractional, vaccines are inactivated vaccines. They do not contain viable pathogens and are safe. Unlike inactivated whole-cell vaccines, they contain only specific parts or fragments of the pathogen.
Subunit vaccines are further divided into three types:
- protein-based subunit vaccines,
- polysaccharide subunit vaccines,
- conjugated subunit vaccines.
Subunit vaccines are further divided into three types:
- protein-based subunit vaccines,
- polysaccharide subunit vaccines,
- conjugated subunit vaccines.
Disadvantages of subunit vaccines
Polysaccharide vaccines have some disadvantages. Specifically, they do not always induce strong and lasting immunity, particularly in children under two years of age, whose immune systems are not yet fully developed. Additionally, repeated vaccination may not necessarily strengthen protection.
Polysaccharide vaccines have some disadvantages. Specifically, they do not always induce strong and lasting immunity, particularly in children under two years of age, whose immune systems are not yet fully developed. Additionally, repeated vaccination may not necessarily strengthen protection.
In the production of a conjugated subunit vaccine, the polysaccharide is bound to a protein carrier, which helps the immune system respond better to the vaccine. As a result, conjugated vaccines are effective even in young children and provide stronger and more lasting immunity.
In the production of a conjugated subunit vaccine, the polysaccharide is bound to a protein carrier, which helps the immune system respond better to the vaccine. As a result, conjugated vaccines are effective even in young children and provide stronger and more lasting immunity.
Toxoid Vaccines
In the production of toxoid vaccines, the toxin produced by a bacterium (such as the causative agent of diphtheria or tetanus) is inactivated to form a toxoid, which is then used as an antigen to induce an immune response.
Since the toxoid alone does not elicit a strong immune response, an adjuvant is added to the vaccine, and multiple doses are required to achieve lasting protection. Toxoid vaccines are safe and have a long shelf life.
In the production of toxoid vaccines, the toxin produced by a bacterium (such as the causative agent of diphtheria or tetanus) is inactivated to form a toxoid, which is then used as an antigen to induce an immune response.
Since the toxoid alone does not elicit a strong immune response, an adjuvant is added to the vaccine, and multiple doses are required to achieve lasting protection. Toxoid vaccines are safe and have a long shelf life.
Combined vaccines
Combined vaccines are biological preparations made from two or more single-component vaccines that can protect a person against several infectious diseases at the same time.
Administering a combined vaccine does not increase the burden on the human immune system.
The indications and contraindications for administering combination vaccines are the same as for monovalent vaccines.
Combined vaccines are biological preparations made from two or more single-component vaccines that can protect a person against several infectious diseases at the same time.
Administering a combined vaccine does not increase the burden on the human immune system.
The indications and contraindications for administering combination vaccines are the same as for monovalent vaccines.
Advantages of using combined vaccines
- Provide good protection against pathogens.
- Are just as effective and safe as monovalent vaccines.
- Reduce the number of vaccine injections and visits to the family health center.
- Help ensure timely vaccination of children against multiple infectious diseases.
- Reduce healthcare costs as well as the costs of transporting, storing, and preserving vaccines.
- Provide good protection against pathogens.
- Are just as effective and safe as monovalent vaccines.
- Reduce the number of vaccine injections and visits to the family health center.
- Help ensure timely vaccination of children against multiple infectious diseases.
- Reduce healthcare costs as well as the costs of transporting, storing, and preserving vaccines.
- They reduce the frequency of potential side effects.
- They increase vaccination coverage among children, which strengthens the general immunity of the population.
- They simplify the addition of new vaccines to the immunization schedule.
- They are much more cost-effective compared to monovalent vaccines.
- They can be used in place of a monovalent vaccine with the same components, and one combination vaccine can be replaced with another combination vaccine with the same antigenic composition.
- They reduce the frequency of potential side effects.
- They increase vaccination coverage among children, which strengthens the general immunity of the population.
- They simplify the addition of new vaccines to the immunization schedule.
- They are much more cost-effective compared to monovalent vaccines.
- They can be used in place of a monovalent vaccine with the same components, and one combination vaccine can be replaced with another combination vaccine with the same antigenic composition.