Vaccines

Vaccines US Medical PG Question 1: A 34-year-old female medical professional who works for a non-governmental organization visits her primary care provider for a routine health check-up. She made a recent trip to Sub-Saharan Africa where she participated in a humanitarian medical project. Her medical history and physical examination are unremarkable. A chest radiograph and a tuberculin skin test (PPD) are ordered. The chest radiograph is performed at the side and the PPD reaction measures 12 mm after 72 hours. Which of the following mechanisms is involved in the skin test reaction?

• A. Complement activation
• B. Formation of immune complexes
• C. Th1-mediated delayed-type hypersensitivity (Correct Answer)
• D. IgE cross-linking

Vaccines Explanation: ***Th1-mediated delayed-type hypersensitivity*** - The **tuberculin skin test (PPD)** is a classic example of a **Type IV hypersensitivity reaction**, which is mediated by **T-helper 1 (Th1) cells** [3]. - Upon re-exposure to mycobacterial antigens (tuberculin), previously sensitized Th1 cells release **cytokines** that recruit and activate **macrophages**, leading to the characteristic induration and erythema [3]. *Complement activation* - This mechanism is primarily involved in host defense against microbial infections and in **Type II** and **Type III hypersensitivity reactions**, not Delayed-Type Hypersensitivity [2]. - Activation of the complement system leads to cell lysis, opsonization, and inflammation, but it does not directly drive the PPD skin test response [2]. *Formation of immune complexes* - This describes a **Type III hypersensitivity reaction**, where **antigen-antibody complexes** deposit in tissues, leading to inflammation and tissue damage [1]. - Examples include serum sickness and Arthus reaction, which are distinct from the cell-mediated PPD response [1]. *IgE cross-linking* - This mechanism is characteristic of **Type I (immediate) hypersensitivity reactions**, commonly known as allergies [4]. - **IgE antibodies** bind to mast cells and basophils; subsequent cross-linking by antigens triggers the release of mediators like histamine, leading to rapid allergic symptoms [4].

Vaccines US Medical PG Question 2: A research team develops a new monoclonal antibody checkpoint inhibitor for advanced melanoma that has shown promise in animal studies as well as high efficacy and low toxicity in early phase human clinical trials. The research team would now like to compare this drug to existing standard of care immunotherapy for advanced melanoma. The research team decides to conduct a non-randomized study where the novel drug will be offered to patients who are deemed to be at risk for toxicity with the current standard of care immunotherapy, while patients without such risk factors will receive the standard treatment. Which of the following best describes the level of evidence that this study can offer?

• A. Level 1
• B. Level 3 (Correct Answer)
• C. Level 5
• D. Level 4
• E. Level 2

Vaccines Explanation: ***Level 3*** - A **non-randomized controlled trial** like the one described, where patient assignment to treatment groups is based on specific characteristics (risk of toxicity), falls into Level 3 evidence. - This level typically includes **non-randomized controlled trials** and **well-designed cohort studies** with comparison groups, which are prone to selection bias and confounding. - The study compares two treatments but lacks randomization, making it Level 3 evidence. *Level 1* - Level 1 evidence is the **highest level of evidence**, derived from **systematic reviews and meta-analyses** of multiple well-designed randomized controlled trials or large, high-quality randomized controlled trials. - The described study is explicitly stated as non-randomized, ruling out Level 1. *Level 2* - Level 2 evidence involves at least one **well-designed randomized controlled trial** (RCT) or **systematic reviews** of randomized trials. - The current study is *non-randomized*, which means it cannot be classified as Level 2 evidence, as randomization is a key criterion for this level. *Level 4* - Level 4 evidence includes **case series**, **case-control studies**, and **poorly designed cohort or case-control studies**. - While the study is non-randomized, it is a controlled comparative trial rather than a case series or retrospective case-control study, placing it at Level 3. *Level 5* - Level 5 evidence is the **lowest level of evidence**, typically consisting of **expert opinion** without explicit critical appraisal, or based on physiology, bench research, or animal studies. - While the drug was initially tested in animal studies, the current human comparative study offers a higher level of evidence than expert opinion or preclinical data.

Vaccines US Medical PG Question 3: A 40-year-old pregnant woman, G4 P3, visits your office at week 30 of gestation. She is very excited about her pregnancy and wants to be the healthiest she can be in preparation for labor and for her baby. What vaccination should she receive at this visit?

• A. Measles, mumps, and rubella (MMR)
• B. Varicella vaccine
• C. Herpes zoster vaccine
• D. Live attenuated influenza vaccine
• E. Tetanus, diphtheria, and acellular pertussis (Tdap) (Correct Answer)

Vaccines Explanation: ***Tetanus, diphtheria, and acellular pertussis (Tdap)*** - The Tdap vaccine is recommended during each pregnancy, preferably between **27 and 36 weeks of gestation**, to maximize maternal antibody response and passive antibody transfer to the fetus. - This provides critical protection against **pertussis (whooping cough)** for the newborn, who is too young to be vaccinated. *Measles, mumps, and rubella (MMR)* - The **MMR vaccine is a live vaccine** and is **contraindicated during pregnancy** due to the theoretical risk of congenital rubella syndrome, although no cases have been reported. - It should be administered **postpartum** if the mother is not immune to rubella. *Varicella vaccine* - The **varicella vaccine is a live vaccine** and is **contraindicated during pregnancy** due to the theoretical risk of congenital varicella syndrome. - Like MMR, it should be offered in the **postpartum period** if the woman is not immune. *Herpes zoster vaccine* - The herpes zoster vaccine is typically recommended for **older adults** (50 years and older) for shingles prevention. - It is **not routinely recommended during pregnancy**, and its safety and efficacy in this population have not been sufficiently established. *Live attenuated influenza vaccine* - The **live attenuated influenza vaccine (LAIV)** is **contraindicated during pregnancy** due to its live virus content. - Pregnant women should receive the **inactivated influenza vaccine (IIV)**, which is safe and recommended during any trimester.

Vaccines US Medical PG Question 4: A 21-year-old woman is diagnosed with a rare subtype of anti-NMDA encephalitis. During the diagnostic workup, she was found to have an ovarian teratoma. Her physician is curious about the association between anti-NMDA encephalitis and ovarian teratomas. A causal relationship between this subtype of anti-NMDA encephalitis and ovarian teratomas is suspected. The physician aims to identify patients with anti-NMDA encephalitis and subsequently evaluate them for the presence of ovarian teratomas. Which type of study design would be the most appropriate?

• A. Case-control study
• B. Retrospective cohort study (Correct Answer)
• C. Cross-sectional study
• D. Case series
• E. Randomized controlled trial

Vaccines Explanation: ***Retrospective cohort study*** - This is the **most appropriate design** because the physician starts with a defined group of patients **with anti-NMDA encephalitis** (the exposure/condition) and then evaluates them for the **presence of ovarian teratomas** (the outcome). - A **cohort study** follows this directional approach: identify individuals with a specific exposure or condition, then assess the frequency or presence of an outcome within that group. - **Retrospective** cohort studies use **existing medical records** to identify the exposed cohort and determine outcome status, making this practical for studying a rare condition like anti-NMDA encephalitis. - This design allows calculation of the **prevalence** of ovarian teratomas among anti-NMDA encephalitis patients and can suggest an association between the two conditions. *Cross-sectional study* - Cross-sectional studies assess **both exposure and outcome simultaneously** at a single point in time in a population, rather than starting with one condition and looking for another. - This design would be appropriate if the physician surveyed a population and assessed both anti-NMDA encephalitis and ovarian teratomas at the same time, but the question describes a **directional evaluation** (first identify encephalitis patients, then evaluate for teratomas). - While cross-sectional studies can identify associations, they do not follow the sequential approach described in the clinical scenario. *Case series* - A **case series** is a descriptive study that reports characteristics or outcomes in a group of patients with a particular condition but lacks a comparison group and does not systematically evaluate associations. - While it could describe ovarian teratoma findings in anti-NMDA encephalitis patients, it does not provide the structured framework for assessing prevalence or association that a cohort study offers. *Case-control study* - **Case-control studies** work in the **opposite direction**: they start with the outcome (e.g., ovarian teratoma cases) and look backward for the exposure (e.g., anti-NMDA encephalitis). - The physician's approach starts with the **exposure first** (anti-NMDA encephalitis), making a case-control design inappropriate. - Case-control studies are efficient for studying rare outcomes but are not aligned with the described study plan. *Randomized controlled trial* - **RCTs** are experimental studies that randomly assign participants to different interventions to evaluate treatment efficacy or causation. - This is an **observational research question** about naturally occurring associations, not an intervention study, making RCTs inappropriate and unethical for this scenario.

Vaccines US Medical PG Question 5: A 12-month-old girl is brought to her pediatrician for a checkup and vaccines. The patient’s mother wants to send her to daycare but is worried about exposure to unvaccinated children and other potential sources of infection. The toddler was born at 39 weeks gestation via spontaneous vaginal delivery. She is up to date on all vaccines. She does not walk yet but stands in place and can say a few words. The toddler drinks formula and eats a mixture of soft vegetables and pureed meals. She has no current medications. On physical exam, the vital signs include: temperature 37.0°C (98.6°F), blood pressure 95/50 mm Hg, pulse 130/min, and respiratory rate 28/min. The patient is alert and responsive. The remainder of the exam is unremarkable. Which of the following is most appropriate for this patient at this visit?

• A. Meningococcal vaccine
• B. Gross motor workup and evaluation
• C. Rotavirus vaccine
• D. Referral for speech pathology
• E. MMR vaccine (Correct Answer)

Vaccines Explanation: ***MMR vaccine*** - The **measles, mumps, and rubella (MMR) vaccine** is recommended for administration at **12-15 months of age**. - This timing offers protection against these common childhood diseases, which is especially important for children attending **daycare**. *Meningococcal vaccine* - The routine **meningococcal vaccine (MenACWY)** is typically recommended for adolescents at **11-12 years of age**, with a booster at 16 years. - While there are specific circumstances for earlier vaccination (e.g., high-risk conditions), it is **not routine** for a 12-month-old. *Gross motor workup and evaluation* - The patient's motor development, standing in place but not yet walking, is **within the normal range** for a 12-month-old. - A definitive **gross motor workup** would generally be considered if there were more significant delays or regressions. *Rotavirus vaccine* - The **rotavirus vaccine** series is typically given at **2, 4, and 6 months of age**, with the final dose administered no later than **8 months of age**. - A 12-month-old is **outside the recommended age range** for initiating or completing this vaccine series. *Referral for speech pathology* - Saying "a few words" at 12 months is **within the normal developmental milestone** for expressive language at this age. - A referral for **speech pathology** would generally be indicated for more significant language delays.

Vaccines Flashcard 1 of 5

Question: What is the best interventional strategy for prevention of neonatal tetanus?_____

Answer: Maternal vaccination w/ toxoid vaccine

Vaccines Flashcard 2 of 5

Question: Which form of poliovirus vaccine provides group immunity with person-to-person contact? _____

Answer: Sabin

Extra Information:   Watch Poliovirus (PicoRNAviridae) [https://dashboard.sketchy.com/study/medical/courses/medical-microbiology/units/medical-microbiology-viruses/videos/medical-microbiology-viruses-rna-viruses-positive-sense-poliovirus-picornaviridae?utm_source=anki&utm_medium=partnership&utm_campaign=february_update&utm_content=medical]Watch associated Bootcamp video [https://app.bootcamp.com/med-school/immunology/videos/vaccinations?index=4] https://onlinemeded.org/spa/pediatrics/vaccinations/acquire?ref=anki 

Vaccines Flashcard 3 of 5

Question: What strain of Haemophilus influenzae is a vaccine available for?_____

Answer: Type B (meningitis causing)

Vaccines Flashcard 4 of 5

Question: Meningococcal vaccine is given between _____

Answer: 11-18 yo

Extra Information:  https://onlinemeded.org?ref=anki 

Vaccines Flashcard 5 of 5

Question: What is the likely diagnosis in a child who recently received the VZV vaccine and developed a maculopapular/vesicular rash with few lesions? _____

Answer: Replication of the vaccine-strain VZV

Extra Information:  https://onlinemeded.org?ref=anki