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VACCINES—MICROBIOLOGY {S1}

VACCINES—MICROBIOLOGY {S1}. BY RANJEET RAMAN. Childhood vaccines may include MMR, Polio, DTP, BCG, Varicella, Hep B .

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VACCINES—MICROBIOLOGY {S1}

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  1. VACCINES—MICROBIOLOGY {S1} BY RANJEET RAMAN

  2. Childhood vaccines may include MMR, Polio, DTP, BCG, Varicella, Hep B. • Smallpox eradication was possible because it was a stable virus with no animal reservoir, ​no subclinical carrier state, prompt antibody response, and an easily recognized ​clinical presentation.

  3. Measles vaccine is live attenuated virus, so it’s heat/light sensitive. It is neutralized by ​antibodies from mother’s milk, so must be given no earlier than 9 months.

  4. Polio vaccine is of two types: • ​Salk: The killed virus type must be injected. Does not provide gut immunity. • ​Sabin: The live attenuated type is given orally and provides gut immunity, but there is a ​ tiny risk of reversion to virulence. It is being used for the eradication campaign.

  5. Diphtheria vaccine is the toxin only. It is combined with pertussis and tetanus vaccines (DPT). • Tetanus vaccine is also a toxin vaccine. • Pertussis is a killed bacteria OR an acellular subunit vaccine. The whole killed virus prep can ​cause fever, prolonged crying, febrile seizures, and hypotonic shock. The acellular ​subunit vaccine is much safer.

  6. Thus the DPT vaccine only consists of toxins and subunits, and cannot itself become infectious. • Hepatitis B vaccine was the first recombinant DNA vaccine. An HBV surface antigen (“S antigen”) ​is grown in yeast and then injected.

  7. BCG vaccine is the only tuberculosis vaccine. It is a live vaccine from attenuated M. bovis. ​If is effective against disseminated/Meningeal TB but not against pulmonary TB. It ​also interferes with PPD test. • Rotavirus vaccine was withdrawn because it causes intussusception.

  8. Haemophilus influenza B is the main cause of bacterial meningitis. The vaccine is purified ​polysaccharide conjugated to a T-cell-stimulating protein such as tetanus toxin. • ​This was the first conjugated vaccine. Conjugation enhances immunogenicity and ​T-cell response.

  9. Strep pneumoniae has 90 serotype variants. Vaccines usually carry around 20 different ​serotype polysaccharide capsules to provide decent coverage. • Meningococcal vaccines cover all serotypes except type B. Type A is epidemic in Sub-​Saharan Africa (the meningitis belt).

  10. Influenza vaccines use whole killed virus or membrane proteins. • ​Antigen drift is the steady accumulation of mutations. It is what necessitates new ​vaccine formulations every year. • ​Antigen shift is the reassortment of genome segments between human and avian ​influenza. Shifts cause major new epidemics.

  11. Yellow Fever vaccine is live attenuated and should never be given to infants! • Anthrax vaccine uses lethal factor, edema factor, and protective factor, but without the capsule. • Smallpox vaccine is the Vaccinia virus.

  12. ERADICATED • ​Smallpox • ​Virus has single serotype • ​Humans are only reservoir • ​No carriers or subclinical infection • ​dz easily recognized so prompt immunization, Ab response also prompt • ​Vaccine is stable and effective

  13. CHILDREN’S VACCINES • ​Measles • ​Live attenuated, heat-sensitive, SQ injection after 9 mo old • ​Coverage in central Africa is poor • ​Polio • Salk (inactivated): safe, injected, protects against paralysis not infection, USA • ​ Sabin (oral): fairly safe, gut immunity, used in EPI

  14. ​DTP (diphtheria, tetanus, pertussis) • ​D,T: inactivated toxin plus alum, P: whole killed, aP: acellular subunit • ​IM injection • ​DTaP has lower adverse reaction rate than DTP • ​Hepatitis B • Recombinant HBsAg made in S. cerevisiae • ​Poor worldwide coverage at present • MMR: live attenuated • ​Hib: capsule polysaccharide linked to carrier (conjugate vaccine) • ​Pneumococcus: multivalent vaccine

  15. ADULT VACCINES • ​Meningococcal: 4-valent vaccine, recommended for college students • ​Influenza: whole killed virus or purified membrane proteins, reformulated each year • TRAVELLER’S VACCINES • ​Hepatitis A: inactivated virus, 2 doses • ​Yellow fever: live attenuated, booster q10yrs, contraindicated > 4 mo old

  16. Japanese encephalitis: whole inactivated virus, used especially for SE Asia • ​Salmonella typhi: two types: Ty21A (oral 6yr+every 5yr), ViCPS (inject 2yr+every 2yr) • Rabies: three types available • BIODEFENSE • ​Anthrax: live attenuated, short term side effects • ​Smallpox: vaccine virus, autoinoculation is primary risk

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