Vaccines

Hepatitis A virus is a fecal-oral RNA virus that causes acute, host-immune-mediated hepatitis with a prodrome followed by jaundice, aminotransferases often exceeding 1,000 U/L, and full recovery in at least 90% of patients within 3 to 6 months. Diagnosis rests on HAV IgM, treatment is supportive, and prevention centers on a 2-dose inactivated vaccine plus prompt postexposure prophylaxis.

Hepatitis B virus is a bloodborne and sexually transmitted DNA virus that causes acute hepatitis and, when infection becomes chronic, progresses through immune-tolerant, immune-active, immune-control, and reactivation phases toward cirrhosis and hepatocellular carcinoma. Diagnosis rests on hepatitis B serology, chronic infection is treated with entecavir or tenofovir, and reactivation during immunosuppression is prevented with prophylactic antiviral therapy.

Herpes zoster is reactivation of latent varicella-zoster virus from a sensory ganglion, producing a painful, dermatomal vesicular rash that does not cross the midline, most common in adults older than 60 years and in immunosuppressed hosts; diagnosis is clinical, confirmed by VZV PCR when needed, and antiviral therapy started within 72 hours of rash onset shortens the illness and reduces postherpetic neuralgia.

Human papillomavirus is a nonenveloped DNA virus with low-risk types (6, 11) that cause warts and high-risk types (16, 18, and others) that drive cervical, anal, vulvar, penile, and oropharyngeal cancer, prevented by 9-valent vaccination and managed by type-specific screening rather than treatment of the virus itself.

Rabies is a bullet-shaped rhabdovirus transmitted by bat, raccoon, skunk, or dog bites that causes a uniformly fatal encephalomyelitis once symptoms begin, marked by hydrophobia and aerophobia. Prevention is everything: thorough wound washing plus rabies immune globulin and vaccine given before symptom onset prevents disease, but there is no effective treatment after clinical rabies develops.

Influenza is an acute orthomyxoviral respiratory illness with abrupt fever, myalgia, and cough, driven by an H and N surface glycoprotein antigenicity that drifts yearly (seasonal epidemics) and occasionally shifts (pandemics). Diagnosis is clinical or confirmed by nucleic acid amplification testing, and neuraminidase-inhibitor or endonuclease-inhibitor antiviral therapy started within 48 hours of onset shortens illness and reduces complications in high-risk patients.

Whooping cough is a highly infectious bronchitis caused by the gram-negative coccobacillus Bordetella pertussis, marked by catarrhal, paroxysmal, and convalescent stages with lymphocytosis; diagnosis is clinical, confirmed by nasopharyngeal PCR, and treated with azithromycin plus prophylaxis of close contacts.

Common variable immunodeficiency is the most common symptomatic primary immunodeficiency, a defect in B-cell differentiation causing low immunoglobulins and recurrent sinopulmonary infections, usually diagnosed after puberty. Diagnosis rests on low IgG with low IgA or IgM plus impaired vaccine responses, and treatment is lifelong immunoglobulin replacement with prompt infection management.