Vaccine-preventable diseases

Vaccine-preventable diseases US Medical PG Question 1: A 1-year-old immigrant girl presents to her pediatrician for a routine well-child check. She has not received any recommended vaccines since birth. She attends daycare and remains healthy despite her daily association with several other children for the past 3 months at a home daycare facility. Which of the following phenomena explains why she has not contracted any vaccine-preventable diseases such as measles, diphtheria, or pertussis?

• A. Genetic shift
• B. Tolerance
• C. Herd immunity (Correct Answer)
• D. Immune evasion
• E. Genetic drift

Vaccine-preventable diseases Explanation: ***Herd immunity*** - Herd immunity occurs when a significant portion of the population is immune to a contagious disease due to vaccination or prior infection, providing indirect protection to unimmunized individuals. - In a daycare setting where other children are likely vaccinated, the presence of immunized individuals reduces the likelihood of transmission to the unimmunized girl. - This is a classic example of **indirect protection** conferred by high vaccination rates in the community. *Genetic shift* - Genetic shift refers to an abrupt, major change in the influenza A virus, leading to new hemagglutinin and/or neuraminidase proteins, resulting in a novel subtype. - This phenomenon explains the emergence of new pandemic influenza strains, not the protection of an unimmunized child from common vaccine-preventable diseases. *Tolerance* - Tolerance in immunology is the failure to mount an immune response to an antigen, often referring to self-antigens. - It does not explain protection from external pathogens in an unvaccinated individual but rather the absence of an immune response to specific antigens. *Immune evasion* - Immune evasion is a strategy used by pathogens to avoid detection and elimination by the host's immune system. - This concept describes how pathogens survive and cause disease despite an immune response, not why an unimmunized host remains healthy. *Genetic drift* - Genetic drift involves small, gradual changes in genes over time, particularly in viruses, leading to antigenic variations. - While it explains the need for updated vaccines (e.g., annual influenza vaccines), it does not account for the protection of an unvaccinated individual from infection by common vaccine-preventable diseases.

Vaccine-preventable diseases US Medical PG Question 2: A 3-year-old boy is brought to the emergency department after the sudden onset of a rash that started on the head and progressed to the trunk and extremities. Over the past week, he has had a runny nose, a cough, and red, crusty eyes. He recently immigrated with his family from Yemen and immunization records are unavailable. The patient appears malnourished. His temperature is 40.0°C (104°F). Examination shows generalized lymphadenopathy and a blanching, partially confluent maculopapular exanthema. Administration of which of the following is most likely to improve this patient's condition?

• A. Live-attenuated vaccine
• B. Retinol (Correct Answer)
• C. Valacyclovir
• D. Penicillin V
• E. Intravenous immunoglobulin

Vaccine-preventable diseases Explanation: ***Retinol*** - This patient presents with classic symptoms of **measles** (rubeola), including **prodromal cough, coryza, conjunctivitis**, followed by a **maculopapular rash** spreading from head to trunk. Given his young age, malnourishment, and recent immigration from a region with likely lower vaccination rates, **vitamin A (retinol) supplementation** is crucial as it reduces morbidity and mortality in measles, especially in malnourished children. - **Vitamin A deficiency** is common in malnourished children and exacerbates the severity of measles, leading to a higher risk of complications like pneumonia, diarrhea, and blindness. *Live-attenuated vaccine* - A **live-attenuated vaccine** (e.g., MMR) is used for **prevention** of measles and is typically given to healthy individuals for immunization, not as a treatment for active infection. - Administering a live vaccine to an acutely ill, febrile child with an ongoing viral infection is **contraindicated** and would not improve his current condition. *Valacyclovir* - **Valacyclovir** is an antiviral medication specifically used to treat **herpesvirus infections** (e.g., herpes simplex, varicella-zoster). - Measles is caused by the **measles virus (a paramyxovirus)**, and valacyclovir has no efficacy against this pathogen. *Penicillin V* - **Penicillin V** is an antibiotic used to treat **bacterial infections**, particularly those caused by gram-positive bacteria. - Measles is a **viral infection**, and antibiotics are not effective against viruses. They would only be considered if a **secondary bacterial infection** (e.g., otitis media, pneumonia) is suspected, which is not the primary issue here. *Intravenous immunoglobulin* - **Intravenous immunoglobulin (IVIG)** can be used for **post-exposure prophylaxis** in susceptible individuals exposed to measles or in immunocompromised patients, but it is not a primary treatment for active, symptomatic measles in an otherwise immunocompetent (though malnourished) child. - While it modulates the immune response, **vitamin A supplementation** has proven efficacy in reducing the severity and complications of measles in children, especially in resource-limited settings.

Vaccine-preventable diseases US Medical PG Question 3: A 27-year-old G0P0 female presents to her OB/GYN for a preconception visit to seek advice before becoming pregnant. A detailed history reveals no prior medical or surgical history, and she appears to be in good health currently. Her vaccination history is up-to-date. She denies tobacco or recreational drug use and admits to drinking 2 glasses of wine per week. She states that she is looking to start trying to become pregnant within the next month, hopefully by the end of January. Which of the following is NOT recommended as a next step for this patient's preconception care?

• A. Begin 400 mcg folic acid supplementation
• B. Administer measles, mumps, rubella (MMR) vaccination (Correct Answer)
• C. Obtain rubella titer
• D. Obtain varicella zoster titer
• E. Recommend inactivated influenza vaccination

Vaccine-preventable diseases Explanation: ***Administer measles, mumps, rubella (MMR) vaccination*** - Live-attenuated vaccines like **MMR** are contraindicated during pregnancy and should ideally be given **at least one month prior to conception**. - If her vaccination history is up-to-date and she plans to conceive within the month, administering MMR is not recommended at this time without confirming immunity first. *Begin 400 mcg folic acid supplementation* - **Folic acid supplementation** at 400 mcg daily is recommended for all women of childbearing age to prevent **neural tube defects**, ideally starting at least one month before conception and continuing through the first trimester. - This is a crucial step in preconception care to ensure adequate levels when the neural tube is forming. *Obtain rubella titer* - Checking a **rubella titer** is standard preconception care to determine immunity, as rubella infection during pregnancy can lead to serious congenital anomalies. - If she is not immune, the MMR vaccine can be offered, but with a **one-month contraception period** before attempting conception. *Obtain varicella zoster titer* - Determining **varicella immunity** is important because congenital varicella syndrome can occur if a non-immune mother contracts chickenpox during pregnancy. - If she is not immune, the **varicella vaccine** can be administered, followed by a **one-month waiting period** before conception. *Recommend inactivated influenza vaccination* - **Inactivated influenza vaccination** is safe and recommended during any stage of pregnancy, including the preconception period, to protect both the mother and newborn from severe influenza outcomes. - It can be given even if she plans to conceive within the month, as it is not a live vaccine.

Vaccine-preventable diseases US Medical PG Question 4: A student health coordinator plans on leading a campus-wide HIV screening program that will be free for the entire undergraduate student body. The goal is to capture as many correct HIV diagnoses as possible with the fewest false positives. The coordinator consults with the hospital to see which tests are available to use for this program. Test A has a sensitivity of 0.92 and a specificity of 0.99. Test B has a sensitivity of 0.95 and a specificity of 0.96. Test C has a sensitivity of 0.98 and a specificity of 0.93. Which of the following testing schemes should the coordinator pursue?

• A. Test A on the entire student body followed by Test B on those who are positive
• B. Test A on the entire student body followed by Test C on those who are positive
• C. Test C on the entire student body followed by Test B on those who are positive
• D. Test C on the entire student body followed by Test A on those who are positive (Correct Answer)
• E. Test B on the entire student body followed by Test A on those who are positive

Vaccine-preventable diseases Explanation: ***Test C on the entire student body followed by Test A on those who are positive*** - To "capture as many correct HIV diagnoses as possible" (maximize true positives), the initial screening test should have the **highest sensitivity**. Test C has the highest sensitivity (0.98). - To "capture as few false positives as possible" (maximize true negatives and confirm diagnoses), the confirmatory test should have the **highest specificity**. Test A has the highest specificity (0.99). *Test A on the entire student body followed by Test B on those who are positive* - Starting with Test A (sensitivity 0.92) would miss more true positive cases than starting with Test C (sensitivity 0.98), failing the goal of **capturing as many cases as possible**. - Following with Test B (specificity 0.96) would result in more false positives than following with Test A (specificity 0.99). *Test A on the entire student body followed by Test C on those who are positive* - This scheme would miss many true positive cases initially due to Test A's lower sensitivity compared to Test C. - Following with Test C would introduce more false positives than necessary, as it has a lower specificity (0.93) than Test A (0.99). *Test C on the entire student body followed by Test B on those who are positive* - While Test C is a good initial screen for its high sensitivity, following it with Test B (specificity 0.96) is less optimal than Test A (specificity 0.99) for minimizing false positives in the confirmation step. - This combination would therefore yield more false positives in the confirmatory stage than using Test A. *Test B on the entire student body followed by Test A on those who are positive* - Test B has a sensitivity of 0.95, which is lower than Test C's sensitivity of 0.98, meaning it would miss more true positive cases at the initial screening stage. - While Test A provides excellent specificity for confirmation, the initial screening step is suboptimal for the goal of capturing as many diagnoses as possible.

Vaccine-preventable diseases US Medical PG Question 5: A 19-year-old male arrives to student health for an annual check up. He is up to date on his infant and childhood vaccinations up to age 10. At age 12, he received a single dose of the tetanus, diphtheria, and acellular pertussis vaccine, and a quadrivalent meningococcal conjugate vaccine. A month ago, he received the influenza vaccine. The patient has no significant medical history. He takes over the counter ibuprofen for occasional headaches. He has a father with hypertension and hyperlipidemia, and his brother has asthma. He is sexually active with his current girlfriend. He denies tobacco use, illicit drug use, and recent or future travel. The patient’s temperature is 98°F (36.7°C), blood pressure is 118/78 mmHg, pulse is 70/min, and respirations are 14/min with an oxygen saturation of 99% O2 on room air. A physical examination is normal. What of the following is the best recommendation for vaccination?

• A. Human papillomavirus vaccine (Correct Answer)
• B. Hepatitis A vaccine
• C. Herpes zoster vaccine
• D. Pneumococcal vaccine
• E. Tetanus and reduced diphtheria toxoid booster

Vaccine-preventable diseases Explanation: ***Human papilloma virus*** - This patient, being 19 years old and **sexually active**, is a prime candidate for the **HPV vaccine** to prevent infections that can lead to various cancers. - The CDC recommends routine HPV vaccination at age 11-12, but catch-up vaccination is recommended for individuals up to age 26 if not adequately vaccinated previously. *Hepatitis A vaccine* - The Hepatitis A vaccine is generally recommended for individuals at **increased risk** of infection, such as travelers to endemic areas, men who have sex with men, or those with chronic liver disease, none of which apply to this patient. - There is no indication for routine vaccination without specific risk factors in this otherwise healthy young male. *Herpes zoster vaccine* - The herpes zoster (shingles) vaccine is recommended for adults **age 50 years and older** to prevent shingles. - This patient is only 19 years old, making him too young for this vaccine recommendation. *Pneumococcal vaccine* - Pneumococcal vaccines (PCV13 and PPSV23) are typically recommended for **young children**, adults **65 years and older**, or individuals with **certain underlying medical conditions** (e.g., chronic heart, lung, or kidney disease, or immunocompromised states). - This 19-year-old patient has no such risk factors for pneumococcal disease. *Tetanus and reduced diphtheria toxoid booster* - The patient received a Tdap vaccine at age 12. A Td booster is recommended **every 10 years** for adults. - Since it has been only 7 years since his last Tdap vaccine, he is not due for a Td booster at this time.

Vaccine-preventable diseases US Medical PG Question 6: A 21-year-old U.S. born first year medical student with no prior hospital or healthcare work presents to the physician for a routine physical exam. The patient is HIV negative, denies drug use, and denies sick contacts. The physician places a purified protein tuberculin test in the patient's right forearm intradermally. What is the proper time to read the test and induration diameter that would indicate a positive test result?

• A. 36 hours and 7mm diameter
• B. 48 hours and 11mm diameter
• C. 72 hours and 16mm diameter (Correct Answer)
• D. 96 hours and 14mm diameter
• E. 24 hours and 18mm diameter

Vaccine-preventable diseases Explanation: ***72 hours and 16mm diameter*** - The **purified protein derivative (PPD) test** should ideally be read between 48 and 72 hours after administration to allow for the **Type IV hypersensitivity reaction** to fully develop. - For individuals with no known risk factors for tuberculosis and no prior exposure, an induration of **≥15 mm** is considered a positive result. A 16mm diameter falls within this range. *36 hours and 7mm diameter* - **36 hours** is too early to accurately read a PPD test, as the delayed-type hypersensitivity reaction may not have fully manifested. - A **7mm induration** would generally be considered negative in a low-risk individual, as the threshold for positivity in this group is higher. *48 hours and 11mm diameter* - While **48 hours** is within the acceptable window for reading a PPD test, an **11mm induration** is not considered positive for a young, low-risk individual without any predisposing conditions like HIV or organ transplant. - The threshold for a positive result in this demographic is typically **≥15 mm**. *96 hours and 14mm diameter* - **96 hours** (4 days) is generally too late to accurately read a PPD test, as the reaction may begin to fade, leading to a potentially false negative. - A **14mm induration** is still below the positive threshold of ≥15mm for a low-risk individual. *24 hours and 18mm diameter* - **24 hours** is significantly too early to read a PPD test, as the immune response will not have fully developed, leading to unreliable results. - While **18mm induration** would be a positive result, the timing makes the reading invalid.

Vaccine-preventable diseases US Medical PG Question 7: An 11-year-old boy is brought to the physician by his mother because of a pruritic generalized rash for 2 days. He returned from a 3-day outdoor summer camp 1 week ago. During his time there, one child was sent home after being diagnosed with measles. The patient was diagnosed with a seizure disorder 6 weeks ago and he has asthma. Current medications include carbamazepine and an albuterol inhaler. His immunization records are unavailable. His temperature is 38.4°C (101.1°F), pulse is 88/min, and blood pressure is 102/60 mm Hg. Examination shows facial edema and a diffuse rash over the face, trunk, and extremities. There is cervical and inguinal lymphadenopathy. The remainder of the examination shows no abnormalities. Which of the following is the most appropriate next step in management?

• A. Perform rapid plasma reagin test
• B. Heterophile antibody test
• C. Discontinue carbamazepine (Correct Answer)
• D. Perform measles serology
• E. Administer penicillin therapy

Vaccine-preventable diseases Explanation: ***Discontinue carbamazepine*** - The patient's symptoms (pruritic generalized rash, facial edema, fever, and lymphadenopathy) developing after starting carbamazepine are highly suggestive of **drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome**, a severe adverse drug reaction. - The first and most critical step in managing **DRESS syndrome** is to immediately **discontinue the offending medication**, which in this case is carbamazepine. *Perform rapid plasma reagin test* - A **rapid plasma reagin (RPR) test** is used to screen for **syphilis**, which typically presents with a different rash morphology (e.g., maculopapular rash on palms and soles in secondary syphilis) and is less likely given the clear temporal association with a new medication. - The patient's symptoms are not consistent with the typical presentation of syphilis, and the priority should be addressing the suspected drug reaction. *Heterophile antibody test* - A **heterophile antibody test** is used to diagnose **infectious mononucleosis**, which can cause fever, rash, and lymphadenopathy. However, the facial edema is less typical, and the clear link to a new medication makes DRESS syndrome a more probable diagnosis. - While infectious mononucleosis can trigger rash, the combination of **facial edema** and the temporal relationship with carbamazepine initiation points more strongly to a drug-induced reaction rather than a primary infection. *Perform measles serology* - Although there was a measles case at the summer camp, the rash associated with **measles** is typically maculopapular, starts on the face, and spreads downward, often accompanied by **Koplik spots** and cough/coryza/conjunctivitis (**the 3 Cs**). - The presence of **facial edema** and the timing relative to carbamazepine initiation make measles less likely as the primary diagnosis requiring immediate action. *Administer penicillin therapy* - **Penicillin therapy** is indicated for bacterial infections, particularly streptococcal infections or syphilis (as mentioned with RPR). - The patient's presentation is more consistent with a **drug-induced hypersensitivity reaction** rather than a bacterial infection, making empirical antibiotic therapy inappropriate as the initial management step.

Vaccine-preventable diseases US Medical PG Question 8: A 28-year-old male presents to his primary care physician with complaints of intermittent abdominal pain and alternating bouts of constipation and diarrhea. His medical chart is not significant for any past medical problems or prior surgeries. He is not prescribed any current medications. Which of the following questions would be the most useful next question in eliciting further history from this patient?

• A. "Does the diarrhea typically precede the constipation, or vice-versa?"
• B. "Is the diarrhea foul-smelling?"
• C. "Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life"
• D. "Are the symptoms worse in the morning or at night?"
• E. "Can you tell me more about the symptoms you have been experiencing?" (Correct Answer)

Vaccine-preventable diseases Explanation: ***Can you tell me more about the symptoms you have been experiencing?*** - This **open-ended question** encourages the patient to provide a **comprehensive narrative** of their symptoms, including details about onset, frequency, duration, alleviating/aggravating factors, and associated symptoms, which is crucial for diagnosis. - In a patient presenting with vague, intermittent symptoms like alternating constipation and diarrhea, allowing them to elaborate freely can reveal important clues that might not be captured by more targeted questions. *Does the diarrhea typically precede the constipation, or vice-versa?* - While knowing the sequence of symptoms can be helpful in understanding the **pattern of bowel dysfunction**, it is a very specific question that might overlook other important aspects of the patient's experience. - It prematurely narrows the focus without first obtaining a broad understanding of the patient's overall symptomatic picture. *Is the diarrhea foul-smelling?* - Foul-smelling diarrhea can indicate **malabsorption** or **bacterial overgrowth**, which are important to consider in some gastrointestinal conditions. - However, this is a **specific symptom inquiry** that should follow a more general exploration of the patient's symptoms, as it may not be relevant if other crucial details are missed. *Please rate your abdominal pain on a scale of 1-10, with 10 being the worst pain of your life* - Quantifying pain intensity is useful for assessing the **severity of discomfort** and monitoring changes over time. - However, for a patient with intermittent rather than acute, severe pain, understanding the **character, location, and triggers** of the pain is often more diagnostically valuable than just a numerical rating initially. *Are the symptoms worse in the morning or at night?* - Diurnal variation can be relevant in certain conditions, such as inflammatory bowel diseases where nocturnal symptoms might be more concerning, or functional disorders whose symptoms might be stress-related. - This is another **specific question** that should come after gathering a more complete initial picture of the patient's symptoms to ensure no key information is overlooked.

Vaccine-preventable diseases US Medical PG Question 9: A 2-year-old boy presents to the pediatrician for evaluation of an elevated temperature, sore throat, runny nose, and lacrimation for the past week, and a rash which he developed yesterday. The rash began on the patient’s face and spread down to the trunk, hands, and feet. The patient’s mother gave him ibuprofen to control the fever. The child has not received mumps, measles, and rubella vaccinations because he was ill when the vaccine was scheduled and was later lost to follow-up. The vital signs include blood pressure 90/50 mm Hg, heart rate 110/min, respiratory rate 22/min, and temperature 37.8°C (100.0℉). On physical examination, the child was drowsy. His face, trunk, and extremities were covered with a maculopapular erythematous rash. Two irregularly-shaped red dots were also noted on the mucosa of the lower lip. The remainder of the physical examination was within normal limits. What is the probable causative agent for this child’s condition?

• A. Group A Streptococcus
• B. Rubulavirus
• C. Influenzavirus
• D. Morbillivirus (Correct Answer)
• E. Herpesvirus

Vaccine-preventable diseases Explanation: ***Morbillivirus*** - The constellation of symptoms—**elevated temperature**, **sore throat**, **runny nose**, **lacrimation**, a **maculopapular erythematous rash** that began on the face and spread downward, and especially the **irregularly-shaped red dots on the mucosa of the lower lip** (likely **Koplik spots**)—are classic for **measles**, caused by Morbillivirus. - The patient's **unvaccinated status** against MMR further supports measles as the most probable diagnosis, as it is a highly contagious disease prevented by vaccination. *Group A Streptococcus* - This bacterium causes **scarlet fever**, characterized by a **sandpaper-like rash** and **strawberry tongue**, not a maculopapular rash spreading from face to extremities with Koplik spots. - While it can cause pharyngitis and fever, the specific rash progression and oral lesions rule out Group A Streptococcus. *Rubulavirus* - Rubulavirus causes **mumps**, which primarily presents with **parotitis** (swelling of parotid glands), fever, and headache. - It does not typically cause a generalized maculopapular rash or Koplik spots, making it an unlikely cause for the described symptoms. *Influenzavirus* - Influenzavirus causes **influenza**, characterized by sudden onset of high fever, cough, myalgia, and headache. - While it can cause fever and respiratory symptoms, it does not typically present with a widespread maculopapular rash or Koplik spots. *Herpesvirus* - Herpesviruses cause a variety of conditions, including **chickenpox** (Varicella-zoster virus), which presents with **vesicular lesions** that crust over, and **roseola infantum** (HHV-6/7), which primarily causes a high fever followed by a non-pruritic rash appearing *after* the fever subsides. - Neither of these typically presents with Koplik spots or the specific maculopapular rash progression described.

Vaccine-preventable diseases US Medical PG Question 10: A 16-year-old female presents to her pediatrician complaining of 2 weeks of fever and 1 week of swollen lumps in her left armpit. Upon examination of the left upper extremity, her physician notes the presence of a single papule which the patient claimed appeared one week ago. The patient started her first job at a pet store 2.5 weeks ago. Which of the following is the vector of transmission of the causative agent?

• A. Cats (Correct Answer)
• B. Rabbits
• C. Animal urine
• D. Parrots
• E. Armadillos

Vaccine-preventable diseases Explanation: ***Cats*** - The combination of **fever**, **swollen lymph nodes** (lumps in the armpit), a **single papule**, and a recent history of working at a **pet store** strongly suggests **cat scratch disease**. - **Cat scratch disease** is caused by *Bartonella henselae*, which is primarily transmitted to humans through the **scratch or bite of a cat**, especially kittens. *Rabbits* - Rabbits are known vectors for diseases like **tularemia**, which can cause fever and swollen lymph nodes. - However, the typical presentation of tularemia often includes a more prominent **ulcerative lesion** at the site of inoculation, and the papule described is less characteristic. *Animal urine* - While animal urine can transmit diseases like **leptospirosis**, which can cause fever and various systemic symptoms, it typically does not present with a localized papule followed by regional lymphadenopathy in this manner. - Exposure to animal urine usually occurs through contact with contaminated water or soil, and the pet store context points more towards direct animal contact. *Parrots* - Parrots are associated with **psittacosis** (parrot fever), caused by *Chlamydia psittaci*. - Psittacosis primarily manifests as a **respiratory illness** (pneumonia) and does not typically present with a localized papule and regional lymphadenopathy. *Armadillos* - Armadillos are significant reservoirs for **Mycobacterium leprae**, the causative agent of **leprosy**. - Leprosy has a very long incubation period and presents with skin lesions, nerve damage, and sometimes lymphadenopathy, but a 2-week onset and the described acute symptoms are inconsistent with leprosy.

Vaccine-preventable diseases Flashcard 1 of 9

Question: Strep pneumonia conjugate vaccine for children produces an Ig_____ response.

Answer: G

Vaccine-preventable diseases Flashcard 2 of 9

Question: Which type of immunization has a rapid onset? _____

Answer: Passive immunization

Vaccine-preventable diseases Flashcard 3 of 9

Question: Which type of immunization is acquired by exposure to foreign antigens? _____

Answer: Active immunization

Vaccine-preventable diseases Flashcard 4 of 9

Question: What virus can present with subacute sclerosing panencephalitis?_____

Answer: Measles (rubeola)

Vaccine-preventable diseases Flashcard 5 of 9

Question: Which type of immunization has a short span of duration? _____

Answer: Passive immunization

Vaccine-preventable diseases Flashcard 6 of 9

Question: _____ is the gold standard used in the diagnosis of Herpes Simplex Virus

Answer: PCR

Vaccine-preventable diseases Flashcard 7 of 9

Question: What vaccinations should be considered for patients without a spleen?

Answer: encapsulated organisms; specifically S. pneumoniae, H influenzae, N. meningitidis

Vaccine-preventable diseases Flashcard 8 of 9

Question: Explain the rationale for "conjugated" vaccines.

Answer: When a vaccine is based on a polysaccharide capsule antigen, the polysaccharide must be attached to a protein in order to induce sufficient immune response.

Vaccine-preventable diseases Flashcard 9 of 9

Question: Considering the relative antigenicity of exotoxins and endotoxins, which class can be used to generate vaccines?

Answer: exotoxins