Diphtheria, tetanus, pertussis US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Diphtheria, tetanus, pertussis. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Diphtheria, tetanus, pertussis US Medical PG Question 1: 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)
Diphtheria, tetanus, pertussis 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.
Diphtheria, tetanus, pertussis US Medical PG Question 2: A 40-year-old man is brought to an urgent care clinic by his wife with complaints of dizziness and blurring of vision for several hours. His wife adds that he has had slurred speech since this morning and complained of difficulty swallowing last night. His wife mentions that her husband was working outdoors and ate stew with roasted beef and potatoes that had been sitting on the stove for the past 3 days. The patient's past medical history is unremarkable. A physical examination reveals right eye ptosis and palatal weakness with an impaired gag reflex. Cranial nerve examination reveals findings suggestive of multiple cranial nerve involvement. What is the mechanism of action of the toxin that is the most likely cause of this patient's symptoms?
- A. Ribosylation of the Gs protein
- B. Inhibition of glycine and GABA
- C. Expression of superantigen
- D. Inhibition of the release of acetylcholine (Correct Answer)
- E. Ribosylation of eukaryotic elongation factor-2
Diphtheria, tetanus, pertussis Explanation: ***Inhibition of the release of acetylcholine***
- The patient's symptoms (dizziness, blurred vision, slurred speech, difficulty swallowing, ptosis, palatal weakness, impaired gag reflex, CN V and VII lesions) are consistent with **botulism**, caused by *Clostridium botulinum* toxin.
- **Botulinum toxin** acts by cleaving SNARE proteins (syntaxin, SNAP-25, and synaptobrevin) at the neuromuscular junction, thereby **inhibiting acetylcholine (ACh) release** from presynaptic terminals and causing flaccid paralysis.
*Ribosylation of the Gs protein*
- This mechanism is characteristic of **cholera toxin** and **heat-labile enterotoxin** of *E. coli*.
- It leads to persistent activation of adenylate cyclase, resulting in increased cyclic AMP and causing **secretory diarrhea**, which is not seen here.
*Inhibition of glycine and GABA*
- This mechanism is associated with **tetanus toxin**, produced by *Clostridium tetani*.
- Tetanus toxin acts by blocking the release of inhibitory neurotransmitters **glycine** and **GABA** in the spinal cord, leading to spastic paralysis and muscle rigidity.
*Expression of superantigen*
- **Superantigens** are toxins produced by bacteria like *Staphylococcus aureus* (e.g., toxic shock syndrome toxin-1) and *Streptococcus pyogenes*.
- They cause widespread activation of T cells, leading to a massive inflammatory response and symptoms like **fever, rash, and hypotension**, rather than neurological deficits.
*Ribosylation of eukaryotic elongation factor-2*
- This is the mechanism of action of **diphtheria toxin**, produced by *Corynebacterium diphtheriae*.
- It inhibits protein synthesis in eukaryotic cells, leading to **cell death** and symptoms like pharyngitis, pseudomembrane formation, and myocarditis, not the paralytic symptoms described.
Diphtheria, tetanus, pertussis US Medical PG Question 3: An 11-year-old boy is brought to his pediatrician by his parents for the routine Tdap immunization booster dose that is given during adolescence. Upon reviewing the patient’s medical records, the pediatrician notes that he was immunized according to CDC recommendations, with the exception that he received a catch-up Tdap immunization at the age of 8 years. When the pediatrician asks the boy’s parents about this delay, they inform the doctor that they immigrated to this country 3 years ago from Southeast Asia, where the child had not been immunized against diphtheria, tetanus, and pertussis. Therefore, he received a catch-up series at 8 years of age, which included the first dose of the Tdap vaccine. Which of the following options should the pediatrician choose to continue the boy’s immunization schedule?
- A. A single dose of Td vaccine at 18 years of age
- B. A single dose of Td vaccine now
- C. No further vaccination needed
- D. A single dose of Tdap vaccine now
- E. A single dose of Tdap vaccine at 13 years of age (Correct Answer)
Diphtheria, tetanus, pertussis Explanation: ***A single dose of Tdap vaccine at 13 years of age***
- The CDC recommends a **minimum interval of 5 years** between Tdap doses when Tdap is given as part of a catch-up series.
- Since this patient received his first Tdap at age 8, the earliest he should receive the adolescent booster is at **age 13** (5 years later).
- This timing ensures adequate spacing while still providing the recommended adolescent booster for **pertussis, tetanus, and diphtheria** protection.
- The 5-year interval prevents excessive antigen exposure and optimizes immune response.
*A single dose of Tdap vaccine now*
- Giving Tdap now would result in only a **3-year interval** from the previous Tdap dose at age 8.
- This violates the CDC recommendation of a **minimum 5-year interval** between Tdap doses.
- Shorter intervals may increase local reactogenicity without improving protection.
*A single dose of Td vaccine now*
- While this would provide tetanus and diphtheria protection, it would **not protect against pertussis**, which is a critical component of adolescent vaccination.
- The Tdap vaccine is specifically recommended for adolescents to boost waning pertussis immunity.
- Additionally, giving it now would still be earlier than the recommended 5-year interval from the previous pertussis-containing vaccine.
*A single dose of Td vaccine at 18 years of age*
- This option would result in a **10-year gap** from the last pertussis-containing vaccine, leaving the adolescent vulnerable during high-risk years.
- The adolescent Tdap booster is specifically timed for ages 11-13 to protect during peak transmission periods in middle and high school.
- Waiting until 18 would miss the critical window for pertussis protection.
*No further vaccination needed*
- While the patient completed a catch-up series, the CDC still recommends an **adolescent Tdap booster** even for those who received Tdap in a catch-up series.
- The adolescent booster is important to maintain immunity against pertussis, which wanes significantly over time.
- The booster should be given at age 13 to maintain the 5-year minimum interval.
Diphtheria, tetanus, pertussis US Medical PG Question 4: A 12-year-old boy is brought by his father to a pediatrician for evaluation of stiff jaw and swallowing difficulty. He has also developed painful body spasms triggered by loud noise, light, and physical touch. His father says that a few days ago, his son continued to play football, even after falling and bruising his arms and knees. On examination, the boy had a sustained facial smile, stiff arched back, and clamped hands. The toxin responsible for these clinical manifestations that travel retrograde in axons of peripheral motor neurons blocks the release of which of the following?
- A. Serotonin
- B. Norepinephrine
- C. Acetylcholine
- D. GABA (gamma-aminobutyric acid) (Correct Answer)
- E. Glutamate
Diphtheria, tetanus, pertussis Explanation: ***GABA (gamma-aminobutyric acid)***
- The patient's symptoms (stiff jaw, swallowing difficulty, painful body spasms, opisthotonos, sustained facial smile, clamped hands) are classic for **tetanus**, caused by **Clostridium tetani** producing **tetanospasmin**.
- **Tetanospasmin** travels retrograde in peripheral motor neurons to the spinal cord where it blocks the release of **inhibitory neurotransmitters**, primarily **GABA and glycine**, from **Renshaw cells** and inhibitory interneurons.
- Loss of inhibition leads to **unopposed excitation** of motor neurons, causing **sustained muscle contractions** (rigidity) and **spasms**.
- **Glycine** is the major inhibitory neurotransmitter in the spinal cord, while **GABA** predominates in the brain; both are affected in tetanus.
*Serotonin*
- Serotonin is a **monoamine neurotransmitter** involved in mood, sleep, appetite, and other functions, and its release is not directly inhibited by tetanospasmin.
- Disruptions in serotonin pathways are associated with psychiatric disorders or specific syndromes like **serotonin syndrome**, which presents differently with hyperthermia, altered mental status, and autonomic instability.
*Norepinephrine*
- Norepinephrine is a **catecholamine** involved in the sympathetic nervous system and "fight or flight" response.
- While **autonomic instability** with sympathetic overactivity can occur in severe tetanus as a complication, norepinephrine release is not the primary target of tetanospasmin.
- Tetanus primarily affects **inhibitory interneurons** in the spinal cord, not adrenergic neurons.
*Acetylcholine*
- Acetylcholine is the primary **excitatory neurotransmitter** at the **neuromuscular junction**, causing muscle contraction.
- In tetanus, acetylcholine release at the neuromuscular junction is **not blocked**; instead, the problem is **lack of inhibition** of motor neurons, leading to **excessive** acetylcholine release and unopposed muscle contraction.
- Contrast this with **botulism** (botulinum toxin), which *does* block acetylcholine release at the neuromuscular junction, causing flaccid paralysis.
*Glutamate*
- Glutamate is the main **excitatory neurotransmitter** in the central nervous system.
- Tetanospasmin does not directly block glutamate release; rather, the loss of inhibitory neurotransmitters (GABA and glycine) leads to **unchecked excitation** of motor neurons by glutamate, contributing to the muscle rigidity and spasms.
Diphtheria, tetanus, pertussis US Medical PG Question 5: A 27-year-old man presents to the emergency department with unrelenting muscle spasms for the past several hours. The patient’s girlfriend states that he started having jaw spasms and soreness last night but now his neck, back, and arms are spasming. She also states that he stepped on a nail about 1 week ago. Past medical history is noncontributory. The patient's vaccination status is unknown at this time. Today, the vital signs include temperature 39.1°C (102.4°F), heart rate 115/min, blood pressure 145/110 mm Hg, and respiratory rate 10/min. On exam, the patient is in obvious discomfort, with a clenched jaw and extended neck. Labs are drawn and a basic metabolic panel comes back normal and the white blood cell (WBC) count is moderately elevated. Which of the following is the most likely etiology of this patient’s symptoms?
- A. An exotoxin that causes ADP-ribosylation of EF-2
- B. An edema factor that functions as adenylate cyclase
- C. A heat-labile toxin that inhibits ACh release at the NMJ
- D. An exotoxin that cleaves SNARE proteins (Correct Answer)
- E. A toxin that disables the G-protein coupled receptor
Diphtheria, tetanus, pertussis Explanation: ***An exotoxin that cleaves SNARE proteins***
- The patient's presentation with **unrelenting muscle spasms**, jaw spasms (**trismus**), extended neck (**opisthotonus**), and a recent **puncture wound** are classic signs of **tetanus**.
- **Tetanospasmin**, the neurotoxin produced by *Clostridium tetani*, acts by cleaving **SNARE proteins**, which are essential for the release of **inhibitory neurotransmitters** (glycine and GABA) from spinal interneurons, leading to uncontrolled muscle contraction.
*An exotoxin that causes ADP-ribosylation of EF-2*
- This mechanism describes **diphtheria toxin**, which is produced by *Corynebacterium diphtheriae* and inhibits protein synthesis in eukaryotic cells.
- While *C. diphtheriae* can cause systemic effects, it primarily manifests as **upper respiratory tract infection** with pseudomembrane formation, lymphadenopathy, and myocarditis, not generalized muscle spasms.
*An edema factor that functions as adenylate cyclase*
- This describes the **edema factor** component of **anthrax toxin**, produced by *Bacillus anthracis*.
- Anthrax typically causes cutaneous, inhalational, or gastrointestinal infections, and its symptoms do not include the generalized muscle spasms seen in this patient.
*A heat-labile toxin that inhibits ACh release at the NMJ*
- This mechanism describes **botulinum toxin**, produced by *Clostridium botulinum*, which causes **flaccid paralysis** by preventing the release of acetylcholine at the neuromuscular junction.
- The patient exhibits muscle spasms and rigidity (**spastic paralysis**), which is directly opposite to the effects of botulinum toxin.
*A toxin that disables the G-protein coupled receptor*
- While various toxins can affect G-protein coupled receptors (e.g., cholera toxin or pertussis toxin), this general description does not specifically match the clinical presentation of tetanus.
- Toxins affecting G-protein coupled receptors typically lead to symptoms like **severe diarrhea** (cholera) or **whooping cough** (pertussis) rather than generalized muscle spasms.
Diphtheria, tetanus, pertussis US Medical PG Question 6: A 34-year-old gravida 5, para 4 presents to the physician for prenatal care at 32 weeks of pregnancy. She comes from a rural region of Ethiopia and did not have appropriate prenatal care during previous pregnancies. She has no complaints of swelling, contractions, loss of fluid, or bleeding from the vagina. During her current pregnancy, she has received proper care and has completed the required laboratory and instrumental tests, which did not show any pathology. Her blood pressure is 130/70 mm Hg, heart rate is 77/min, respiratory rate is 15/min, and temperature is 36.6°C (97.8°F). Her examination is consistent with a normal 32-weeks’ gestation. The patient tells the physician that she is going to deliver her child at home, without any medical aid. The physician inquires about her tetanus vaccination status. The patient reports that she had tetanus 1 year after her first delivery at the age of 16, and it was managed appropriately. She had no tetanus vaccinations since then. Which of the following statements is true?
- A. The patient should receive at least 2 doses of tetanus toxoid within the 4-week interval to ensure that she and her baby will both have immunity against tetanus. (Correct Answer)
- B. The antibodies from tetanus immune globulin vaccine, if given to a pregnant woman, would not cross the placental barrier.
- C. Even if the patient receives appropriate tetanus vaccination, it will be necessary to administer toxoid to the newborn.
- D. The patient is protected against tetanus due to her past medical history, so only the child is at risk of developing tetanus after an out-of-hospital delivery.
- E. The patient does not need vaccination because she has developed natural immunity against tetanus and will pass it to her baby.
Diphtheria, tetanus, pertussis Explanation: ***The patient should receive at least 2 doses of tetanus toxoid within the 4-week interval to ensure that she and her baby will both have immunity against tetanus.***
- For unvaccinated or incompletely vaccinated pregnant women, the **CDC recommends a series of at least two doses of tetanus toxoid-containing vaccine (Tdap or Td)**. These doses should be given at least 4 weeks apart to provide sufficient maternal protection and ensure the transfer of **passive immunity** to the newborn.
- This regimen ensures that both the mother and the baby receive protection against tetanus, particularly crucial in settings of **home delivery without medical aid** where the risk of exposure is higher.
*The antibodies from tetanus immune globulin vaccine, if given to a pregnant woman, would not cross the placental barrier.*
- **Tetanus immune globulin (TIG)** provides immediate, but short-lived, passive immunity and its antibodies **do cross the placental barrier**.
- However, TIG is not routinely used for prenatal vaccination; **tetanus toxoid (Tdap/Td)** is administered to stimulate active antibody production in the mother and subsequent passive transfer to the fetus.
*Even if the patient receives appropriate tetanus vaccination, it will be necessary to administer toxoid to the newborn.*
- If the mother receives **appropriate tetanus vaccination (Tdap/Td) during pregnancy**, sufficient **maternal antibodies are transferred to the newborn** via the placenta, protecting the infant during the first few months of life.
- Therefore, the newborn typically does not require immediate tetanus toxoid administration at birth if the mother was adequately vaccinated during pregnancy; their primary series of vaccinations begins later.
*The patient is protected against tetanus due to her past medical history, so only the child is at risk of developing tetanus after an out-of-hospital delivery.*
- While prior tetanus infection can provide some immunity, it is **not always long-lasting or fully protective**, and it does not guarantee protection for future pregnancies or the newborn.
- Therefore, the mother should still be vaccinated to ensure both her and the baby's protection, especially when delivering in a high-risk environment.
*The patient does not need vaccination because she has developed natural immunity against tetanus and will pass it to her baby.*
- **Natural immunity to tetanus following infection is often insufficient and may not be long-lasting**, unlike immunity conferred by vaccination.
- Therefore, vaccination is still recommended to ensure adequate immunity for the mother and to facilitate the transfer of protective antibodies to the baby.
Diphtheria, tetanus, pertussis US Medical PG Question 7: A 9-year-old girl presents with a 3-week history of cough. Her mother reports that initially, she had a runny nose and was tired, with a slight cough, but as the runny nose resolved, the cough seemed to get worse. She further states that the cough is dry sounding and occurs during the day and night. She describes having coughing spasms that occasionally end in vomiting, but between episodes of coughing she is fine. She reports that during a coughing spasm, her daughter will gasp for air and sometimes make a “whooping” noise. A nasopharyngeal swab confirms a diagnosis of Bordetella pertussis. Which of the following statements apply to this patient?
- A. She should be started on azithromycin for more rapid resolution of cough.
- B. Her classmates should be treated with clarithromycin as prophylaxis.
- C. She will have lifelong natural immunity against Bordetella pertussis.
- D. Her 3-month-old brother should be treated with azithromycin as prophylaxis. (Correct Answer)
- E. Her classmates should receive a Tdap booster regardless of their vaccination status.
Diphtheria, tetanus, pertussis Explanation: ***Her 3-month-old brother should be treated with azithromycin as prophylaxis.***
- The patient's 3-month-old brother is at a very high risk of severe pertussis due to his age and direct exposure, making **post-exposure prophylaxis (PEP)** crucial.
- **Azithromycin** is the recommended antibiotic for PEP in infants due to its efficacy and safety profile.
*She should be started on azithromycin for more rapid resolution of cough.*
- While **azithromycin** is the recommended treatment for pertussis, it is primarily effective in reducing the transmission of *Bordetella pertussis* if started early in the **catarrhal stage**.
- Once the patient is in the **paroxysmal (whooping cough) stage**, as described by the 3-week cough and "whooping" noises, antibiotics **do not significantly shorten the duration or severity of the cough**.
*Her classmates should be treated with clarithromycin as prophylaxis.*
- **Classmates** are generally considered at lower risk for severe disease compared to household contacts, and routine prophylaxis for an entire classroom is not typically recommended unless there is a specific outbreak investigation or direct close contact.
- If prophylaxis were considered for close contacts, **azithromycin** is generally preferred over clarithromycin in children due to fewer drug interactions and a more convenient dosing schedule.
*She will have lifelong natural immunity against Bordetella pertussis.*
- **Natural immunity** following a pertussis infection is not lifelong; it wanes over time, typically within a few years.
- This is why **booster vaccinations (Tdap)** are recommended for adolescents and adults to maintain protection.
*Her classmates should receive a Tdap booster regardless of their vaccination status.*
- **Tdap boosters** are recommended for adolescents and adults, but giving a booster *regardless of vaccination status* to all classmates is not the standard immediate public health response for isolated pertussis cases.
- Public health guidance often focuses on identifying and vaccinating **unvaccinated** or **under-vaccinated close contacts**, rather than providing universal boosters for an entire class.
Diphtheria, tetanus, pertussis US Medical PG Question 8: A microbiology student was given a swab containing an unknown bacteria taken from the wound of a soldier and asked to identify the causative agent. She determined that the bacteria was a gram-positive, spore-forming bacilli, but had difficulty narrowing it down to the specific bacteria. The next test she performed was the Nagler's test, in which she grew the bacteria on a plate made from egg yolk, which would demonstrate the ability of the bacteria to hydrolyze phospholipids and produce an area of opacity. Half the plate contained a specific antitoxin which prevented hydrolysis of phospholipids while the other half did not contain any antitoxin. The bacteria produced an area of opacity only on half of the plate containing no antitoxin. Which of the following toxins was the antitoxin targeting?
- A. Alpha toxin (Correct Answer)
- B. Exotoxin A
- C. Tetanus toxin
- D. Diphtheria toxin
- E. Botulinum toxin
Diphtheria, tetanus, pertussis Explanation: ***Alpha toxin***
- The scenario describes a **Nagler's test**, which is specifically used to detect the presence of **alpha toxin (lecithinase)** produced by *Clostridium perfringens*.
- The antitoxin prevents the hydrolysis of phospholipids and the formation of opacity, confirming that the opacity is due to the alpha toxin.
*Exotoxin A*
- **Exotoxin A** is a toxin produced by *Pseudomonas aeruginosa* and inhibits protein synthesis.
- It is not associated with the **Nagler's test** or phospholipid hydrolysis on egg yolk agar.
*Tetanus toxin*
- **Tetanus toxin** is produced by *Clostridium tetani* and causes spastic paralysis by inhibiting inhibitory neurotransmitter release.
- It is not involved in phospholipid hydrolysis or detected by the **Nagler's test**.
*Diphtheria toxin*
- **Diphtheria toxin** is produced by *Corynebacterium diphtheriae* and inhibits protein synthesis, leading to cellular death.
- This toxin is not detected by the **Nagler's test** and does not cause phospholipid hydrolysis.
*Botulinum toxin*
- **Botulinum toxin** is produced by *Clostridium botulinum* and causes flaccid paralysis by inhibiting acetylcholine release at the neuromuscular junction.
- It is not associated with the **Nagler's test** or the hydrolysis of phospholipids.
Diphtheria, tetanus, pertussis US Medical PG Question 9: A 23-year-old man presents to student health for a cough. The patient states he has paroxysms of coughing followed by gasping for air. The patient is up to date on his vaccinations and is generally healthy. He states he has felt more stressed lately secondary to exams. His temperature is 101.0°F (38.3°C), blood pressure is 125/65 mmHg, pulse is 105/min, respirations are 14/min, and oxygen saturation is 98% on room air. Laboratory values are notable for the findings below.
Hemoglobin: 12 g/dL
Hematocrit: 36%
Leukocyte count: 13,500/mm^3 with a lymphocytosis
Platelet count: 197,000/mm^3
Physical exam is notable for clear breath sounds bilaterally. Which of the following is the best next step in management?
- A. Azithromycin (Correct Answer)
- B. PCR for Bordetella pertussis
- C. Chest radiograph
- D. Culture
- E. Penicillin
Diphtheria, tetanus, pertussis Explanation: ***Azithromycin***
- This patient's symptoms (paroxysmal cough followed by gasping), fever, and **lymphocytosis**, despite being vaccinated, are highly suggestive of **pertussis** (whooping cough).
- **Macrolide antibiotics** like azithromycin are the recommended treatment for pertussis, as they can reduce the duration and severity of symptoms and prevent transmission, especially when given early in the disease course.
*PCR for Bordetella pertussis*
- While a **PCR test** would confirm the diagnosis, the prompt asks for the **best next step in management**, implying treatment rather than diagnosis given the clear clinical picture.
- Due to the highly contagious nature of pertussis, treatment should ideally be initiated promptly based on clinical suspicion, especially within the **catarrhal** or early **paroxysmal stage**, without waiting for PCR results.
*Chest radiograph*
- A chest radiograph is generally **not indicated** for uncomplicated pertussis, as clear breath sounds are noted and it is usually a clinical diagnosis.
- It would be more relevant to rule out complications like **pneumonia**, which is not immediately suggested by the given information.
*Culture*
- **Bacterial culture** for *Bordetella pertussis* from a nasopharyngeal swab is a diagnostic tool, but it is **less sensitive** and **takes longer** to yield results compared to PCR.
- Given the urgency for treatment to reduce transmission and symptoms, culture is not the most appropriate *next step in management*.
*Penicillin*
- Penicillin is **not effective** against *Bordetella pertussis* as *B. pertussis* is **a** Gram-negative bacterium that is inherently resistant to penicillins.
- **Macrolide antibiotics** are the drug class of choice for pertussis due to their efficacy against this organism.
Diphtheria, tetanus, pertussis US Medical PG Question 10: A 34-year-old man comes to the physician for a routine health maintenance examination. He was diagnosed with HIV 8 years ago. He is currently receiving triple antiretroviral therapy. He is sexually active and uses condoms consistently. He is planning a trip to Thailand with his partner to celebrate his 35th birthday in 6 weeks. His last tetanus and diphtheria booster was given 4 years ago. He received three vaccinations against hepatitis B 5 years ago. He had chickenpox as a child. Other immunization records are unknown. Vital signs are within normal limits. Cardiopulmonary examination shows no abnormalities. Leukocyte count shows 8,700/mm3, and CD4+ T-lymphocyte count is 480 cells/mm3 (Normal ≥ 500); anti-HBs is 150 mIU/mL. Which of the following recommendations is most appropriate at this time?
- A. Yellow fever vaccine
- B. Hepatitis B vaccine
- C. Tetanus, diphtheria, pertussis vaccine (Tdap)
- D. Measles, mumps, rubella vaccine
- E. No vaccination (Correct Answer)
Diphtheria, tetanus, pertussis Explanation: ***Correct: No vaccination***
- Given the patient's current immunization status and clinical scenario, **none of the listed vaccines are indicated at this time**.
- His CD4+ count of 480 cells/mm³ indicates relatively preserved immune function on effective antiretroviral therapy.
- His **anti-HBs level of 150 mIU/mL** demonstrates **adequate hepatitis B immunity** (protective level ≥10 mIU/mL).
- His **tetanus-diphtheria booster was given 4 years ago**, and routine boosters are recommended every **10 years**, so he is not due for another 6 years.
*Incorrect: Yellow fever vaccine*
- **Thailand is not a yellow fever endemic country**, so yellow fever vaccination is **not required or recommended** for travel there.
- Yellow fever vaccine is a **live attenuated vaccine** that can be given to HIV-positive patients with **CD4+ counts ≥200 cells/mm³** when travel to endemic areas (parts of Africa and South America) is necessary.
- Since the patient has a CD4+ count of 480 and Thailand doesn't require this vaccine, this is not applicable.
*Incorrect: Hepatitis B vaccine*
- The patient's **anti-HBs level of 150 mIU/mL** indicates **adequate protective immunity** against hepatitis B.
- A level ≥10 mIU/mL is considered protective, so **no booster is needed**.
*Incorrect: Tetanus, diphtheria, pertussis vaccine (Tdap)*
- **Tetanus-diphtheria boosters are recommended every 10 years**.
- The patient received his last booster **4 years ago**, so he is **not due** for another booster at this time.
- There is no specific indication for **pertussis vaccination** (e.g., pregnancy, close contact with infants).
*Incorrect: Measles, mumps, rubella vaccine*
- **MMR is a live attenuated vaccine** that is **contraindicated** in HIV-positive individuals with **CD4+ counts <200 cells/mm³**.
- While this patient's CD4+ count is 480, MMR should only be given to HIV patients if they lack immunity and have CD4 ≥200.
- There is **no documented need** for MMR based on the clinical scenario provided, and his immunity status to these infections is unknown.
- Without evidence of susceptibility or specific exposure risk, vaccination is not indicated.
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