Vaccine Types And Benefits: What You Need To Know

by Adekunle-Segun.O., Omosimua Shedrack.O., Ajayi Toluwani

Introduction

Infectious disease lead to an exponential increase in mortality rate around the world. The clinical management of infectious disease is most times limited by strains which are resistant to multiple drugs thereby making vaccination a viable mechanism to prevent them.

Vaccines give active acquired immunity against infectious disease. They are biological agents. A vaccine normally contain an agent that has similarities with the microorganism that causes the disease. Often times, they are weakened or killed forms of the microorganisms, toxins or protein which are found inside cell membranes of complex organisms. It stimulates the immune system to view the agent contained in the vaccine as a threat thereby causing it to attack it and any of such organism it encounters later.

In the year 1796, smallpox vaccine was developed. It was the first vaccine ever. Today, several methods are now used in vaccine production. These different methods are referred to as vaccine technologies. Today, the most advanced, modern and best technologies are used in vaccine development. The type of vaccine to be used is dependent on the pathogen which it is designed to target. Vaccines can come in different forms such as oral, injection via needle as well as nasal spray.

TYPES OF VACCINES

There are six different types of vaccines which are:

1. Live attenuated vaccines
2. Inactivated vaccines

• Subunit vaccines

1. Toxoid vaccines
2. Viral vector vaccines
3. Messenger RNA vaccines.

LIVE ATTENUATED VACCINES

They are vaccines which make use of weakened form of the micro-organism. That is, the micro-organism is still alive but now attenuated. They are made by selecting strains of the microorganism which is still capable of producing a strong immune response but not capable of causing disease. They were one of the earliest methods of inducing immune responses which are positive. Live attenuated vaccines give immune response which last long for a lifetime after 1 or 2 doses of the vaccine this is because they have similarities to the infection.

However, they contain minute quantity of the weakened virus. Therefore before taking the vaccine, it is very important that people who intend to take it seek the guidance of their health care provider before deciding to get it especially those whose immune systems are not strong or people who had an organ transplant. Also, there have been challenges with transporting them to countries where refrigerator access is a challenge because they need to be stored at -15^oC or lower till the time of administration.

Some of the benefits of live attenuated vaccines include:

1. They are highly effective in disease prevention
2. They contribute to herd immunity

• Fewer doses are required to confer lifelong immunity

1. They confer natural immunity. This is due to the fact that they mimic the process of natural infection.

Examples include;

1. Chickenpox vaccine
2. Mumps vaccine

• Measles vaccine and

1. Rubella vaccine.

INACTIVATED VACCINES

For this type of vaccine, a live pathogen is killed or inactivated then used to trigger the immune system to produce antibodies to fight the pathogen. By the time it is introduced to humans via a shot, the pathogen which has been inactivated does not have the capability of causing disease. However, in order to get full protection, it is important to most times take several doses. Inactivated vaccines provide a long lasting immune response to the pathogen.

Inactivated vaccines storage temperature depend on the specific vaccine. It is therefore necessary to follow the temperature prescribed by the manufacturer. Mostly, they are stored at temperatures ranging from 2^oC – 8^oC.

Some of the benefits of inactivated vaccines include:

1. Safe for individuals with weakened immune systems
2. There is low risk of disease transmission

• They are effective against new strains.

1. Less expensive than live attenuated vaccines

They are used in protecting individuals against the following diseases;

1. Flu
2. Polio

• Rabies

1. Hepatitis A and
2. Influenza

SUB UNIT VACCINES

They are manufactured by the isolation and purification of specific components of the pathogen. They therefore do not contain the live organism.

Types of subunit vaccines include conjugate vaccines, protein-based vaccines and polysaccharide vaccines.

• Polysaccharide vaccines

In this type of subunit vaccine, immune response is generated by the exposure of the immune system to a coat of sugar from the pathogen. They help to provide defensive responses against the pathogen and gives the body a chance to eliminate the bacteria. Polysaccharide vaccines are contraindicated in children under 2 years of age.

• Conjugate vaccines

Conjugate vaccines contains a polysaccharide unit which is fixed to a protein. This improves the response of the immune system to the sugar on the bacteria. Also, they help in the recognition of the bacteria in future. They work in children under 2 years of age.

• Protein-based vaccines

In this type of sub-unit vaccines, immune response is induced against proteins which can be found on the surface of bacteria, virus or toxin which aids the immune system in defending the body against an infection or toxin.

Subunit vaccines are beneficial to those who are not eligible to take live vaccines such as individuals who are immunocompromised.  Some sub unit vaccines require booster doses for immunity maintenance while others provide long lasting immunity.

Subunit vaccines are sensitive to temperature changes. Therefore, refrigeration or freezing may be required to maintain their potency. Some subunit vaccines require refrigeration between 2^oC to 8^oC while others require freezing at -15^oC to -50^oC.

Some benefits of subunit vaccines include:

1. They only contain a segment of the entire organism, hence do not cause infection.
2. Higher stability than vaccines which contain whole organism.

Examples of subunit vaccines include:

1. Shingles vaccine
2. Hepatitis B vaccine

• Acellular pertussis vaccine

1. Pneumococcal vaccine

TOXOID VACCINES

For toxoid vaccines, toxins which are made by the pathogen are targeted using inactivated toxins instead of targeting the bacteria directly. They give the immune system the ability to neutralize the toxins produced by the pathogen.

Booster shots are sometimes needed for additional protection every 10 years.

Toxoid vaccines are stored at temperatures between 2⁰C to 8⁰C. Freezing is not a requirement in the storage of this type of vaccines.

Benefits of toxoid vaccines include:

1. Safety is guaranteed when toxoid vaccine is administered
2. They are effective against diseases caused by toxins.

Toxoid vaccines are effective against:

1. Tetanus
2. Pertussis

• Diphtheria
• VIRAL VECTOR VACCINES

Viral vector vaccines were researched by scientist for several decades and have been utilized in Ebola and Covid-19 vaccines in recent years. Also, research studies are now focused on viral vector vaccines for zika, HIV and flu.

The mechanism used in viral vector vaccine is the modification of another virus as a vector to strengthen the immune system. They basically make use of a harmless virus to deliver the gene of the antigen in which the immune system is expected to combat.

Viruses used as vectors include adenovirus, measles virus, influenza virus and vesicular stomatitis virus. Some COVID-19 vaccines under trial make use of adenovirus as a viral vector.

Usually, one dose is enough to activate immunity though boosters are sometimes needed for immunity maintenance.

Viral vector vaccines are usually stored at temperature between 2⁰C to 8⁰C.

Some benefits of viral vector vaccines include:

1. With viral vector vaccines, large amount of cells are targeted.
2. They activate a strong immunity for the individuals that take the vaccine.

Examples of viral vector vaccines include:

1. COVID-19 vaccine (Johnson & Johnson and AsrtraZeneca)
2. Ebola vaccine

MESSENGER RNA (mRNA) VACCINES

Messenger RNA made in the laboratory is used to configure the body cells to produce a particular protein which triggers the immune system to defend the body against the pathogen.

This technology has been in constant research by scientist for decades and was utilized in the manufacture of some COVID-19 vaccines. It is one of the latest technologies used in vaccine manufacture. It can be developed speedily by making use of the genetic code of the pathogen and therefore useful in cases of global pandemic in which vaccines are urgently needed to combat.

Studies have shown that when frozen at temperature of -25^oC, they are stable for up to 6 months on storage while at temperature of 4⁰C, they are stable for up to a month.

They are much more beneficial in comparison to other technologies used in vaccine manufacture, this is because the individuals taking the vaccines do not face a risk of getting infected as live virus is not contained in the vaccine. It can also be easily adapted, this is because the formulation of the RNA can be changed to make a new antigen its target.

Examples of mRNA include:

• Pfizer-BioNTech COVID-19 vaccine

How COVID-19 Vaccines work

COVID-19 vaccines helps to trigger immune response to covid-19 virus without the individual getting infected. The process of producing novel vaccines for public use involves very important steps which must be followed. All vaccine types function in different ways to give protection. Just like every other type of vaccine, it leaves the body with memory B-lymphocytes and T-lymphocytes which allows the immune system to recognize the virus if it encounters it again.

Though it may take some weeks for the immune system to produce the memory B and T lymphocytes after vaccination which means one can still be infected if exposed to the virus the first few weeks after vaccination.  Post vaccination, it is possible that the individual experience symptoms like fever which shows that the body immunity is being strengthened.

Presently, the common types of COVID-19 vaccines are Protein subunit, mRNA and viral vector vaccines. They all help the immune system in the recognition and fighting of covid-19 virus without infecting the individual with the virus.

COVID-19 vaccines do not make use of live virus so cannot cause infection when administered. They also do not have any interaction with the DNA nor genetic composition.

Conclusion

Vaccines play a crucial role in safeguarding public health by preventing the spread of infectious diseases and reducing their impact on individuals and communities. There are various types of vaccines, each designed to stimulate the immune system’s response and provide protection against specific pathogens.

REFERENCES

1. Understanding six types of vaccine technology available at https://www.pfizer.com
2. Vaccine types available at https://www.hhs.gov
3. Understanding how covid-19 vaccines work available at https://www.cdc.gov

Source: NAFDAC