Preventing Infectious Diseases: Active Immunization and Vaccines

Restricting the spread and disease severity of the COVID-19 virus are some of the main challenges with regards to combatting the ongoing pandemic. Nanotechnology is a strong tool as it enables development of technology that can be utilized to combat the disease, e.g. diagnosis, dissemination prevention and vaccination. (Find more on Nanotechnology here.)

Vaccination is one of the strongest tools with regards to fighting infectious diseases. Vaccination is a method of introducing immunization in an individual. It greatly reduces the burden of infectious diseases as it reduces symptomatic disease development as well as prevent further transmission of the vira [1]. This reduces the burden of disease on the national health care systems.

Immune System Response

In all simplicity, immunization is a stimulation of the immune system. This stimulation induces the production of antibodies that can neutralize the stimulus [2]. A vaccine utilizes the immunization that happens when the immune system is exposed to new antigens. However, the infectious agent is replaced with a modified agent that poses as the infectious agent. The modification ensures that no harm or disease is developed. 

The immune stimulation is begun by introducing a modified pathogen (disease inducing organism) to the immune system. This can be done by e.g. injecting an inactivated virus. Different proteins are present on the surface of the pathogen. These allow the pathogen to e.g. adhere to cells in the body and infect the cells [3]. 

Some of these surface proteins are unique for the pathogen in question. These are known as antigens. [4]. These are the particles that the immune system will react to by producing antibodies that are specific to each type of antigen. Each antibody enables the immune system to quickly identify and neutralize any organism that contains the specific antigen on its surface [5].

However, the immune system needs time to react and develop specific antibodies when first exposed to a new antigen. This delay is where the live pathogen has time to multiply and cause symptomatic disease [4]. However, no or only mild disease development occurs if the immune response is triggered by an attenuated or inactivated pathogen as part of a vaccine. If the immune system encounters the antigen again, it is able to immediately confine and destroy the invading organism [6, 7]. This means that any subsequent infection with the same pathogen will result in no or a mild, short course of the disease.

Active Immunization and Vaccine Development

Active immunization has been applied for multiple centuries with the first examples documented in China in the 16th century during a smallpox outbreak [8]. Active immunization at that time was the deliberate exposure of a disease to an individual without modification of the infectious agent. The goal was to induce a mild disease progression while, simultaneously, activating the immune system. This would immunize the subject and prevent smallpox from developing due to any future exposure [8].

A second breakthrough in active immunization arose in the 18th century where vaccines with live, attenuated organisms saw first light [8]. This later progressed into vaccine development based on virus or cell cultures with inactivated disease vectors [8]. 

One of the latest technological approaches to vaccine development is the use of genetic engineering. Genetic manipulation enables the expression of surface proteins from any pathogen, e.g. a virus [2]. The proteins will activate the immune system and immunization process when injected into an individual. The use of genetic engineering thus enables vaccination without introducing the actual pathogen to the vaccine recipient.

mRNA Vaccine Used Against COVID-19

The target antigens of COVID-19 are 180-200 kDa, which corresponds approximately to a size of 5 nm [9]. This means that nanotechnology is needed in order to design a vaccine against COVID-19.

A radically new approach to vaccination has been developed recently. It relies on genetic engineering of mRNA and does not entail introducing any proteins or attenuated pathogens into the body [10]. This means that the vaccine does not cause any disease during the immunization process [11]. This type of vaccine was one of the first COVID-19 vaccine types to be approved for use.

The vaccine consists of a DNA-sequence that encodes the antigen or antigens that are unique to the target pathogen. However, the sequence is injected in the form of mRNA (messenger RNA) which prevents the sequence from permanently integrating itself into the genome of the individual [11,12]. Instead, it only acts as a transient carrier of the genetic information and will degrade over time.

The mRNA in the vaccine enables in situ production of the antigen. This means that the antigen for which the immune response is desired is produced directly in the body of the vaccinated individual. The produced antigen will then trigger the same immune response as if the individual had been exposed to the actual pathogen [11,12]. 

This means that no pathogen – either attenuated or inactivated will ever have entered the body. Instead, the natural protein production environment in our body is used to build the immunization that enables protection against e.g. COVID-19. This also removes the potential side effects of mild symptoms during the immunization process.

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[1] World Health Organization (WHO). “Vaccination greatly reduces disease, disability, death and inequity worldwide.” Bulletin of the World Health Organization, WHO, 2008, Accessed, January 2021, at

[2] Murray, Kenneth, et al. “Genetic engineering applied to the development of vaccines.” Philosophical Transactions of the Royal Society of London, B. Biological Sciences, vol. 324, no. 1224, 1989, pp. 461-476.

[3] Science Direct. “Surface Proteins.” Science Direct Topics, Science Direct, 2020, Accessed, January 2021, at

[4] The Immunisation Advisory Centre. “The immune system and immunisation.” Immunisation, January 2020, accessed, January 2021, at

[5] Britannica. Antibody, accessed, January 2021, at

[6] Siegrist, Claire-Anne. “Vaccine immunology.” Vaccines, 5 ed., Saunders, 2008, pp. 17-36.

[7] World Health Organization(WHO). “DNA Vaccines.”, WHO, 2007, Accessed, January 2021, at

[8] Plotkin, Stanley A. History of Vaccine Development. Springer Science & Business Media, 2011.

[9] Huang, Yuan, et al. “Structural and functional properties of SARS-CoV-2 spike protein: potential antivirus drug development for COVID-19.” Acta Pharmacologica Sinica, vol 41, no 9, 2020, pp. 1141-1149.

[10] Bert Hubert, Reverse Engineering the source code of the BioNTech/Pfizer SARS-CoV-2 Vaccine, December 2020, accessed, January 2021, at

[11] Okay, Sezer, et al. “Nanoparticle-based delivery platforms for mRNA vaccine development.” AIMS Biophysics, vol. 7, no. 4, 2020, pp. 323-338.

[12] Schlake, Thomas, et al. “Developing mRNA-vaccine technologies.” RNA Biology, vol. 9, no. 11, 2012, pp. 1319-1330.

2 thoughts on “Preventing Infectious Diseases: Active Immunization and Vaccines”

  1. Hey Sif and The Nano Future Team
    Great article btw 😀 Love reading them on a weekly basis and getting a better insight to the vast applications of nanotechnology. I may have one slight correction to this article. You have written this: “Each antibody enables the immune system to quickly identify and neutralize any organism that contains the specific antibody on its surface ” But I think you mean “…the specific antigen on its surface” 😀
    Great day to you all 😀

    1. Sif Fink Arnbjerg-Nielsen

      Hi Arshwinth,
      Yes, you are completely right. The error has now been corrected.
      Thank you for your kind words regarding our content!

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