biology

Typhoid vaccine

Typhoid vaccine is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Typhoid vaccine rather than just read about it. In short: Typhoid vaccines are vaccines that prevent typhoid fever. Several types are widely available: typhoid conjugate vaccine (TCV), Ty21a (a live oral vaccine) and Vi capsular polysaccharide vaccine (ViPS) (an injectable subunit vaccine).

Key takeaways

Typhoid vaccine belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Typhoid vaccine to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Typhoid vaccine from memory before moving on to harder problems.

Reference excerpt

Typhoid vaccines are vaccines that prevent typhoid fever. Several types are widely available: typhoid conjugate vaccine (TCV), Ty21a (a live oral vaccine) and Vi capsular polysaccharide vaccine (ViPS) (an injectable subunit vaccine). Depending on the type, typhoid vaccines are estimated to be about 50% to 85% effective. The Vi-rEPA vaccine is efficacious in children. The World Health Organization (WHO) recommends vaccinating all children in areas where the disease is common. Otherwise they recommend vaccinating those at high risk. Vaccination campaigns can also be used to control outbreaks of disease. Depending on the vaccine, additional doses are recommended every three to seven years. In the United States the vaccine is only recommended in those at high risk such as travelers to areas of the world where the disease is common. The vaccines available as of 2018 are very safe. Minor side effects may occur at the site of injection. The injectable vaccine is safe in people with HIV/AIDS and the oral vaccine can be used as long as symptoms are not present. While it has not been studied during pregnancy, the non-live vaccines are believed to be safe while the live vaccine is not recommended. The first typhoid vaccines were developed in 1896 by Almroth Edward Wright, Richard Pfeiffer, and Wilhelm Kolle. Due to side-effects newer formulations are recommended as of 2018. It is on the World Health Organization's List of Essential Medicines.

Medical uses Ty21a, the Vi capsular polysaccharide vaccine, and Vi-rEPA are effective in reducing typhoid fever with low rates of adverse effects. Newer vaccines such as Vi-TT (PedaTyph) are awaiting field trials to demonstrate efficacy against natural exposure. The oral Ty21a vaccine prevents around one-half of typhoid cases in the first three years after vaccination. The injectable Vi polysaccharide vaccine prevented about two-thirds of typhoid cases in the first year and had a cumulative efficacy of 55% by the third year. The efficacy of these vaccines has only been demonstrated in children older than two years. Vi-rEPA vaccine, a new conjugate form of the injectable Vi vaccine, may be more effective and prevents the disease in many children under the age of five years. In a trial in 2-to-5-year-old children in Vietnam, the vaccine had more than 90 percent efficacy in the first year and protection lasted at least four years.

Schedule Depending on the formulation it can be given starting at the age of two (ViPS), six (Ty21a), or six months (TCV).

Types Vi capsular polysaccharide vaccine: Typhim VI (Sanofi Pasteur); Typherix (GSK) Ty21a oral vaccine: Vivotif (Bavarian Nordic) Typhoid conjugate vaccine: Typbar-TCV (Bharat Biotech) Combined hepatitis A and Vi polysaccharide vaccine: ViVaxim and ViATIM (Sanofi Pasteur); Hepatyrix (GSK) Activated whole cell vaccine remains available in some parts of the developing world as of 2008.

References

External links Typhoid-Paratyphoid Vaccines at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

Illustrations

Worked examples

Example 1 — a first encounter with Typhoid vaccine

Start with the simplest possible case. Write down what Typhoid vaccine claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Typhoid vaccine before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Typhoid vaccine ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Typhoid vaccine

In research: Typhoid vaccine appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Typhoid vaccine in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Typhoid vaccine is common in secondary-school and first-year university syllabi. It links to neighbouring topics Live vaccines, Typhoid fever, Vaccines by disease, so understanding it makes those chapters shorter.
In everyday life: Look for Typhoid vaccine outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Typhoid vaccine in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Typhoid vaccine means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Typhoid vaccine out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Typhoid vaccine in simple terms?

Why does Typhoid vaccine matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Typhoid vaccine?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Typhoid vaccine.