Exercises: Vaccines, transplants and donation

Explain what a vaccine is, what it contains, and how it prepares the body to defend itself against a disease without suffering from it.

State what a vaccination schedule is, why some vaccines are administered at specific ages, and name two vaccines included in the childhood and adolescent immunization schedule in the United States.

Explain what it means to be a blood donor, what basic requirements are asked of donors, and why regular donation is necessary even when there are no emergencies.

Explain the difference between preventing a disease and curing it, using a vaccine and a medicine as examples.

Name three donations a person can make to help other patients and state what type of patients each one helps.

Explain what a transplant is and cite two organs or tissues that are frequently transplanted, indicating which health problem each one solves.

State whether these statements are true or false and justify your answer: a) getting vaccinated also indirectly protects people who cannot be vaccinated; b) donating blood weakens the donor for months; c) in the United States organ donation is altruistic and is not paid for.

Explain what mild side effects can appear in the days after a vaccine and why they are usually a sign that the immune system is responding.

The tetanus vaccine requires booster doses every few years, whereas others provide lifelong protection with few doses. Explain, based on how immunological memory works, why some protection weakens over time.

The two diagrams represent the same outbreak in two populations with different vaccination coverage (green: vaccinated people; gray: unvaccinated people; red: infected people; the orange crosses in diagram A indicate blocked transmissions). Explain why in diagram A the infection does not advance whereas in B it spreads in a chain reaction, what this "herd immunity" consists of, and what risk is posed by a decrease in vaccination coverage.

Rejection can occur in an organ transplant. Explain why the recipient's immune system attacks the transplanted organ, what blood types and compatibility are, and what medications are used to prevent rejection.

Explain why babies start being vaccinated in the first months of life, which serious diseases are avoided in this way, and what risk delaying the vaccination schedule would have.

A person claims: "I don't get vaccinated because I never get sick". Analyze this argument taking herd immunity into account, and reason what would happen if many people thought the same way.

The flu vaccine is given every fall, whereas the measles vaccine is given in childhood and protects for decades. Explain, relating it to the characteristics of each virus and to immune memory, why some vaccines must be repeated and others do not.

Explain what blood types are, why it is essential to know them before a transfusion, and which type can donate red blood cells to anyone.

Explain what bone marrow donation consists of, what type of patients it can cure, and why it is so difficult to find a compatible donor.

A research team develops two experimental vaccines against a new respiratory virus: vaccine A uses the whole attenuated virus, while vaccine B introduces only fragments of the external protein that the virus uses to attach to human cells (surface antigen).

1. a) Justify why the body of a person who receives vaccine B will be able to neutralize the real virus if they come into contact with it later on, even though the vaccine only contained a fragment.
2. b) During trials, it is observed that in immunocompromised patients, vaccine A can cause mild symptoms of the disease, while vaccine B is completely harmless but requires a booster dose. With this data, justify which of the two vaccines you would recommend administering as a priority in a hospital to elderly people or those with weakened immune systems.

In many countries, a person can donate blood from the age of 18 if they meet the requirements. Each donation (about $450\ \text{mL}$) is separated into three components (red blood cells, plasma, and platelets) and can help up to three patients, but these components expire: platelets last only about $5$ days and red blood cells about six weeks. If a hospital needs $25$ units of blood components per day, calculate how many donations are needed as a minimum each week and reason, based on the expiration of the components, why donating only after major disasters is not enough.

On an internet forum you read this statement: "We shouldn't get the new vaccine against pathogen X. In its clinical trial with 10,000 volunteers, 0.3 % developed fever and muscle pain. A safe vaccine should have zero risk before being approved."

1. a) Knowing that natural infection by pathogen X causes severe complications in 8 out of every 100 infected people (8 %), compare both figures and explain what the benefit-risk balance means in the approval of medicines.
2. b) Refute the statement by arguing biologically why it is impossible to guarantee "zero risk" in any medical treatment and what guarantees the phases of clinical trials provide before a vaccine reaches the general population.

Measles is one of the most contagious viruses in existence: to maintain community or herd immunity and halt its transmission, at least 95 % of the population needs to be vaccinated. In a town of 20,000 inhabitants, vaccination coverage has dropped to 86 % over the last two years. Living in this town are Emma, a 4-month-old baby who is not yet old enough to be vaccinated, and Mateo, a boy undergoing cancer treatment who cannot receive the vaccine because of a weakened immune system.

1. a) Predict what will happen in that town if a person infected with measles attends a crowded party, comparing the current scenario (86 %) with the previous one (95 %).
2. b) Based on the case of Emma and Mateo, justify biologically why a person's decision not to get vaccinated is not just an individual choice regarding their own health, but directly endangers the most vulnerable members of the community.

In a hospital, brain death (the irreversible cessation of all brain activity, maintaining oxygenation and heartbeat through artificial life support) is certified in a young patient following an accident. The patient left no document stating their wishes regarding organ donation. In Spain, "presumed consent" applies, whereby every person is a donor unless they expressed the contrary in life. However, the transplant coordination team always meets with the family to ask for their consent before proceeding.

1. a) The family, in shock, is hesitant because they see that the monitor shows a pulse and they believe that the patient "could still wake up". Justify what medical and biological arguments the coordinator should provide to explain the difference between a reversible coma and brain death.
2. b) Reason why you think the Spanish model always seeks agreement with the family instead of applying the law automatically and compulsorily, and what consequences acting without their consent would have on public trust in the health care system.

Unit challenge. Become a public health advisor for your town by designing a community awareness campaign.

1. Check on the official ONT website (ont.es) the organ donor rate for your autonomous community in 2023 and compare it with Spain's average for that same year ($48.9$ donors per million inhabitants). In addition, survey $4$ family members, asking them which diseases (infectious or non-infectious) they have had this year and their vaccination status.

2. Organize the survey data in a table. In a short text, describe how the body's defenses (barriers or antibodies) acted against one of the recorded infections and justify the immunological memory mechanism provided by vaccines.

3. Create a digital brochure titled "Health and Solidarity" where you propose daily guidelines to prevent non-infectious diseases, explain the collective benefit of vaccination, and provide two arguments to promote organ and tissue donation to address the need for transplants.

Assessment criteria:

• Thorough distinction between pathologies and correct explanation of the immune response and vaccines.

• Adequate collection, comparison, and analysis of data from the ONT and the survey.

• Scientific consistency, creativity, and clarity of the final proposal.