LQB301 Microbiology Report: Herd Immunity Analysis

This report delves into crucial aspects of microbiology, beginning with an in-depth explanation of herd immunity, its mechanisms, and its significance in protecting populations, particularly those unable to be vaccinated. The report then explores the development and function of vaccines, emphasizing their role in combating various diseases and highlighting the importance of antigenic drift and shift in influenza viruses. Furthermore, it addresses antimicrobial resistance, its causes, and the role of antimicrobial stewardship in mitigating this growing threat. The report provides evidence-based guidelines and strategies to promote the effective use of antimicrobials, ultimately aiming to improve patient outcomes and reduce the spread of resistant microorganisms. The report also includes references to support the information provided.

Running head: MICROBIOLOGY 1
Microbiology
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Herd immunity
‘Herd immunity’ according to the World Health Organization, is the immunization of a
significant proportion of a population as a measure to protect individuals who have not
developed immunity and are at risk of infection from the particular disease or condition (Metcalf,
Ferrari, Graham, & Grenfell, 2015). Herd immunity is effective when majority of the people are
protected by vaccination against either a bacteria or virus making it quite impossible for the
disease to spread since the proportion of vulnerable people left is low.
It is one of the best approach to prevent spread of diseases in particular communities.
Studies acknowledge that is pivotal when protecting people who cannot be immunized. Some of
the people who cannot be vaccinated include children who are so young to be immunized,
individuals with compromised immune system and finally, those people who are too sick to be
immunized like some cancer patients. However, Betsch, Böhm, Korn, & Holtmann argue that the
percentage of the population that should be immunized to achieve herd immunity vary depending
with the disease to be prevented (Betsch, Böhm, Korn, & Holtmann, 2017). This means that the
proportion of population to be immunized to achieve herd immunity in influenza for example, is
different from the population to be immunized to prevent measles. Relevant stakeholders should
ensure that the proportion of those vaccinated remains relatively high throughout since a
breakdown in immunization rates subsequently breaks down herd immunity thus increasing the
incidence of the infection (Mallory, Lindesmith, & Baric, 2018). A good example is the outbreak
of measles in UK and pertussis in the United States of America.

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How immunization protect the body against a particular disease
Scientists acknowledge that development of vaccines is one of the greatest achievements
in healthcare. Vaccines have made it possible to eliminate serious infections like smallpox as
well as eliminating 95% of common childhood infections like diphtheria, measles as well as
polio. However, studies note that despite the advancements, 1.5 million people die globally as a
result of vaccine preventable diseases (Sprochi, 2018). Vaccines work in a very unique way.
Vaccines are basically inactivated form of the pathogen or disease. Once they are introduced into
the body, the body produces antibodies against the vaccine. Memory cells then develop such that
when the vaccinated individual comes into contact with the pathogen, the antibodies fight back
even before the infection is manifested thereby preventing the vaccinated individual from a
similar pathogen.
Importance of antigenic drift and antigenic shift in influenza virus for human
diseases
The influenza viruses are rapidly changing through two different ways. The two are
antigenic drift and antigenic shift. Antigenic drift refers to small changes in the genes that make
up the influenza viruses. This is a continuous process that takes place as the virus replicates. The
genetic changes leads to production of viruses that are closely related to another (Kim, Webster,
& Webby, 2018). The new viruses are located close to each other as shown by the phylogenetic
tree. Since the new viruses share common antigenic properties, it becomes easier for the immune
system to combat them if at all they had encountered a similar virus previously. This
phenomenon is described by scientists as cross protection.

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With time however, antigenically new viruses different from those on the phylogenetic
tree might develop. Once this happens, it becomes very difficult for the immune system to
identify and combat the new influenza viruses.
Antigenic shift in influenza virus is the process by which a new influenza subtype A with
new hemagglutinin and neuraminidase combination is formed. In most cases, the new
combination is from animal population and it is very unique to that in humans. Since the human
body has never encountered such a combination, it becomes difficult for the immune system to
combat this new influenza A subtype (Marintcheva, 2016). A good example of the ‘antigenic
shift’ was the one that occurred in the spring of 2009 where the H1N1 that had a combination of
new genes emerged and infected several people creating a pandemic. The only good thing is that
in as much as antigenic drift happens frequently, the dangerous antigenic shift rarely happens.
Role of antimicrobial stewardship in reducing antimicrobial resistance
Drug/antimicrobial resistance according to the Centre for Disease Control is the rapid
evolution of micro-organisms such that they become insensitive to antibiotics used to eliminate
them. This is a phenomenon that has been experienced ever since antibiotics were developed in
the 1930s (Schuts et al., 2016). Drug resistance infections are an increasing concern due to the
slow pace of discovering new antibiotics, poor IPC practices, little investments in research about
new antimicrobials and finally the misuse of antimicrobials both in human and animal health.
Antimicrobial stewardship, is an initiative with the aim of advocating for effective use of
antimicrobials by implementing strategies that focus on preventing the misuse of antimicrobials
to ensure best outcomes both for people and the healthcare setting (Dyar, Huttner, Schouten, &
Pulcini, 2017). Antimicrobial stewardship reduce antimicrobial resistance through providing

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evidence based guidelines that are regularly updated and audited. Furthermore, the antimicrobial
stewardship also ensure that any antibiotic consumption in hospitals is reported. Finally, the
stewardship ensures that actions with the aim of addressing suboptimal prescription of antibiotics
are implemented.

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References
Betsch, C., Böhm, R., Korn, L., & Holtmann, C. (2017). On the benefits of explaining herd
immunity in vaccine advocacy. Nature Human Behaviour, 1(3), 0056.
doi:10.1038/s41562-017-0056
Dyar, O., Huttner, B., Schouten, J., & Pulcini, C. (2017). What is antimicrobial stewardship?
Clinical Microbiology and Infection, 23(11), 793-798. doi:10.1016/j.cmi.2017.08.026
Kim, H., Webster, R. G., & Webby, R. J. (2018). Influenza Virus: Dealing with a Drifting
and Shifting Pathogen. Viral Immunology, 31(2), 174-183.
doi:10.1089/vim.2017.0141
Mallory, M. L., Lindesmith, L. C., & Baric, R. S. (2018). Vaccination-induced herd
immunity: Successes and challenges. Journal of Allergy and Clinical Immunology,
142(1), 64-66. doi:10.1016/j.jaci.2018.05.007
Marintcheva, B. (2016). Modeling Influenza Antigenic Shift and Drift with LEGO Bricks †.
Journal of Microbiology & Biology Education, 17(2), 300-301.
doi:10.1128/jmbe.v17i2.1096
Metcalf, C., Ferrari, M., Graham, A., & Grenfell, B. (2015). Understanding Herd Immunity.
Trends in Immunology, 36(12), 753-755. doi:10.1016/j.it.2015.10.004
Schuts, E. C., Hulscher, M. E., Mouton, J. W., Verduin, C. M., Stuart, J. W.,
Overdiek, H. W., … Prins, J. M. (2016). Current evidence on hospital antimicrobial
stewardship objectives: a systematic review and meta-analysis. The Lancet Infectious
Diseases, 16(7), 847-856. doi:10.1016/s1473-3099(16)00065-7
Sprochi, A. (2018). Book Review: Vaccines: History, Science, and Issues. Reference & User
Services Quarterly, 57(4), 307. doi:10.5860/rusq.57.4.6723