Post-Exposure Prophylaxis: Bites, Rabies, Tetanus & Close Contacts
The right shot or pill, for the right exposure, before the clock runs out
Bite wounds: care and antibiotic prophylaxis
Wound care comes first. Dog bites are the most common animal bites, but cat bites become infected far more often because slender teeth drive saliva deep into tissue. Every bite gets high-pressure saline irrigation, debridement of devitalized tissue, exploration for tendon, joint or bone involvement, and a radiograph when a fracture or retained tooth is possible, plus an assessment of tetanus and rabies risk.
To close or not. Well-vascularized, cosmetically important wounds (face, scalp) may be closed after thorough irrigation. Puncture wounds, hand and foot wounds, crush injuries, delayed presentations and wounds in immunocompromised hosts are left open for delayed closure.
Prophylactic antibiotics. A 3–5 day course of amoxicillin-clavulanate is indicated for cat and human bites; wounds of the hand, foot, genitals or near a joint; deep punctures and crush injuries; wounds that are sutured; and hosts who are immunocompromised, asplenic or cirrhotic (including heavy alcohol use). A superficial dog bite away from the hand in a healthy person usually needs wound care alone. For penicillin allergy, combine doxycycline, TMP-SMX or a fluoroquinolone with clindamycin or metronidazole for anaerobes; clindamycin alone misses Pasteurella and Eikenella. Established infection is treated with amoxicillin-clavulanate or, when severe, IV ampicillin-sulbactam.
Organisms by bite source
| Source | Key organisms | Clinical clue |
|---|---|---|
| Cat | Pasteurella multocida; staphylococci, streptococci, anaerobes | Painful cellulitis within 12–24 h; tenosynovitis, septic arthritis or osteomyelitis from deep punctures |
| Dog | Pasteurella canis, staphylococci, streptococci, anaerobes, Capnocytophaga canimorsus | Lower infection rate; Capnocytophaga sepsis with purpura fulminans, DIC and gangrene in asplenic, alcoholic/cirrhotic or immunocompromised hosts |
| Human | Eikenella corrodens, viridans streptococci, S. aureus, oral anaerobes | Clenched-fist injury over an MCP joint → septic arthritis, extensor tenosynovitis |
Pasteurella and Capnocytophaga. Pasteurella multocida, a gram-negative coccobacillus, is penicillin-susceptible but poorly covered by dicloxacillin, cephalexin and clindamycin, so amoxicillin-clavulanate is the default. Capnocytophaga canimorsus, a fastidious gram-negative rod in dog saliva, can follow a trivial bite or a lick on broken skin; because it causes fulminant sepsis in asplenic or alcoholic hosts, they receive antibiotics after any dog bite.
The fight bite. Punching someone in the mouth drives oral flora through a small knuckle laceration into the MCP joint capsule and extensor tendon, and the wound seals as the fist opens. Any such wound needs a radiograph and hand-surgery exploration with irrigation. Infected wounds receive IV ampicillin-sulbactam; uninfected wounds receive amoxicillin-clavulanate prophylaxis. Eikenella is resistant to clindamycin and metronidazole. Human bites can also transmit HBV, HCV and HIV, so bloodborne exposure should be considered.
Rabies post-exposure prophylaxis
Why prophylaxis is everything. Rabies virus travels retrogradely along nerves to the CNS over an incubation of usually 1–3 months; once symptoms begin, the disease is almost uniformly fatal. An exposure is a bite that breaks the skin, or saliva or neural tissue contacting an open wound or mucous membrane; petting an animal or touching its blood, urine or feces is not.
Which animals. In the US, bats cause most human cases, and raccoons, skunks, foxes and coyotes are the main terrestrial reservoirs. Bites from these animals are treated as rabid unless the animal is captured and its brain tests negative, in which case PEP can be stopped. Squirrels, rats, mice, hamsters, gerbils, rabbits and hares almost never transmit rabies; large rodents such as groundhogs are occasional exceptions. Worldwide, dogs cause most human deaths, so dog bites in countries with canine rabies warrant PEP.
Bats. Bat teeth can leave marks too small to notice. PEP is indicated after direct bat contact when a bite cannot be ruled out, including a person who wakes to find a bat in the room, or a bat found with an unattended child or an intoxicated or cognitively impaired adult, unless the bat is captured and tests negative.
Dogs, cats and ferrets. A healthy animal that bites is confined and observed for 10 days; an animal shedding virus in its saliva will develop signs or die within that window. PEP starts only if the animal becomes ill. A rabid-appearing animal means immediate PEP plus euthanasia and brain testing. When the animal cannot be found, public-health officials help decide based on local epidemiology.
- Wound careScrub with soap and water for about 15 minutes and apply a virucidal agent such as povidone-iodine.
- HRIG (never vaccinated)Human rabies immune globulin 20 IU/kg, infiltrated into and around the wound as far as anatomically feasible; any remainder IM at a site distant from the vaccine. Do not exceed the dose, and do not give it after day 7 of the vaccine series.
- Vaccine1 mL IM in the deltoid (anterolateral thigh in small children, never the gluteus) on days 0, 3, 7 and 14.
- ImmunocompromisedAdd a fifth dose on day 28 and check neutralizing antibody titers afterward.
Previously vaccinated patients. Anyone who completed pre-exposure vaccination or a prior PEP course gets vaccine on days 0 and 3 only. HRIG is omitted because it would blunt the rapid anamnestic response. Pre-exposure vaccination is offered to veterinarians, animal handlers, cavers and some travelers.
There is no deadline for rabies PEP: start it even weeks or months after an exposure if the patient remains asymptomatic. Pregnancy is not a contraindication.
Tetanus prophylaxis
Clostridium tetani spores live in soil and animal feces. Wound management depends on two questions: is the wound clean and minor, and how many tetanus toxoid doses has the patient had?
| Prior toxoid doses | Clean, minor wound | All other wounds |
|---|---|---|
| <3 doses or unknown | Td/Tdap; no TIG | Td/Tdap plus TIG 250 units IM |
| ≥3 doses | Td/Tdap only if ≥10 years since the last dose | Td/Tdap only if ≥5 years since the last dose; no TIG |
Product choice. Tdap is preferred for adults who have never received it and is given in every pregnancy; otherwise Td or Tdap is acceptable, and children under 7 receive DTaP. TIG and vaccine are given at separate sites with separate syringes. Patients with HIV or severe immunodeficiency receive TIG for contaminated wounds regardless of vaccination history. Underimmunized patients should complete the primary series afterward.
Clinical tetanus. Tetanospasmin blocks release of inhibitory neurotransmitters (glycine, GABA), so an underimmunized patient days to weeks after a wound develops trismus (lockjaw), risus sardonicus, opisthotonus, and painful generalized spasms with a clear sensorium; autonomic instability is a late killer. The diagnosis is clinical. Treat with human TIG, wound debridement, metronidazole, benzodiazepines for spasms (with airway support), and a quiet ICU; give tetanus toxoid too, because the disease does not confer immunity.
Close contacts of infectious patients
| Exposure | Who | Prophylaxis and timing |
|---|---|---|
| Neisseria meningitidis | Household, childcare contacts, roommates; direct oral-secretion exposure (kissing, unprotected intubation or suctioning, mouth-to-mouth) in the 7 days before onset | Rifampin for 2 days, single-dose ciprofloxacin, or single-dose IM ceftriaxone (pregnancy); ideally within 24 h |
| Pertussis | All household contacts; high-risk contacts (infants, third-trimester pregnancy, those in contact with them) | Azithromycin for 5 days (TMP-SMX alternative after 2 months of age); within 21 days of the index cough |
| Varicella | Nonimmune healthy people ≥12 months | Varicella vaccine within 3–5 days |
| Varicella, high risk | Nonimmune pregnant women, immunocompromised patients, newborns of mothers with onset 5 days before to 2 days after delivery | VariZIG as soon as possible, up to 10 days |
| Measles | Nonimmune contacts ≥6 months who can receive live vaccine | MMR within 72 h |
| Measles, cannot vaccinate | Infants <6 months (IM); nonimmune pregnant women and severely immunocompromised patients (IV) | Immune globulin within 6 days |
Meningococcal details. Chemoprophylaxis eradicates nasopharyngeal carriage and is given regardless of the contact's vaccination status; throat cultures do not guide the decision. Casual contacts and most health care workers do not qualify. Rifampin turns secretions orange, stains contact lenses and reduces oral contraceptive efficacy. Where ciprofloxacin-resistant strains circulate, public-health authorities recommend an alternative agent.
Pertussis details. Prophylaxis is given regardless of the contact's vaccination status. In infants younger than 1 month, azithromycin is preferred because erythromycin is associated with infantile hypertrophic pyloric stenosis.
Varicella and MMR vaccines are live: never give them to pregnant or severely immunocompromised contacts. Immune globulin is their protection.
Occupational bloodborne exposures
Immediate steps. Wash the wound with soap and water and flush mucous membranes with water. Do not squeeze the wound or apply bleach or other caustic agents. Report the exposure at once, test the source (HBsAg, HCV antibody with reflex RNA, rapid HIV antigen/antibody) and draw the worker's baseline anti-HBs, HCV antibody and HIV test.
Hepatitis B. A vaccinated worker with documented anti-HBs ≥10 mIU/mL needs nothing. An unvaccinated or nonimmune worker exposed to an HBsAg-positive or high-risk unknown source receives HBIG plus the first dose of the vaccine series, ideally within 24 hours. Known nonresponders after two vaccine series exposed to such a source receive two doses of HBIG a month apart; a negative source needs nothing.
Hepatitis C. Neither immune globulin nor antivirals are recommended as HCV PEP. If the source is HCV-positive or unknown, the worker is tested for HCV RNA 3–6 weeks after exposure and for HCV antibody at 4–6 months. Infection is cured with direct-acting antivirals.
HIV. After a significant exposure to blood or infectious fluid from a source with known or possible HIV, start PEP as soon as possible, ideally within hours and no later than 72 hours. The regimen is three drugs: an integrase inhibitor (dolutegravir or bictegravir) plus tenofovir and emtricitabine, taken for 28 days. Do not wait for source results to give the first dose; stop PEP if the source tests negative. Repeat HIV testing over the following months. The same 72-hour rule applies to nonoccupational exposures such as sexual assault.