What is the recommended treatment for smallpox?

Smallpox Treatment

There is no proven effective treatment for clinical smallpox disease; management consists of supportive care only, with strict isolation and infection control measures being paramount to prevent transmission. 1

Primary Management Approach

Supportive Care

• Medical care for seriously ill smallpox patients includes supportive measures exclusively - no specific therapies with proven treatment effectiveness exist 1
• Supportive care addresses symptoms including fever management, fluid resuscitation, pain control, and management of secondary bacterial infections 1
• Consider isolation outside hospital settings when patient condition allows, to prevent healthcare-associated transmission and avoid overtaxing medical resources 1

Critical Isolation Requirements

• Implement airborne precautions using negative air-pressure rooms with high-efficiency particulate air (HEPA) filtration for all confirmed or suspected smallpox patients 1
• Healthcare personnel must use strict contact and airborne precautions: gowns, gloves, eye shields, correctly fitted N-95 masks, and shoe covers 1
• Patients remain infectious from symptom onset until all scabs have separated 1
• Nonhospital isolation facilities require nonshared ventilation systems with access limited to recently vaccinated persons with demonstrated immunity 1

Post-Exposure Prophylaxis

Vaccination Strategy

• Smallpox vaccine can prevent or decrease disease severity when administered within 3-4 days after exposure 1
• Vaccinate all persons with face-to-face, household, or close-proximity contact (<6.5 feet) with confirmed or suspected smallpox patients 1
• Vaccinate children regardless of age if definite exposure risk exists 1
• Vaccinate pregnant women with definite exposure despite pregnancy being a contraindication in non-outbreak settings, as smallpox infection poses greater risk than vaccination 1

Investigational Antiviral Agents

While no FDA-approved treatments exist for smallpox disease itself, several antivirals have been developed under the FDA Animal Rule:

Tecovirimat (ST-246/TPOXX)

• Oral antiviral approved in 2018 for smallpox treatment based on animal efficacy studies 2, 3, 4
• Targets F13L gene product required for extracellular virus production 1
• Demonstrated 100% survival in nonhuman primates challenged with variola virus when treatment started at 2 or 4 days post-infection 4
• Dosing: 600 mg twice daily for 14 days in adults 3
• Well-tolerated with no pattern of troubling adverse events in human safety trials 3

Brincidofovir (CMX001/Tembexa)

• Second oral agent approved for smallpox treatment with different mechanism of action than tecovirimat 5
• Nucleotide analogue DNA polymerase inhibitor with improved oral bioavailability compared to cidofovir 1, 5
• Primary adverse events: gastrointestinal symptoms and transient hepatotoxicity 5
• Black box warning for excessive deaths in hematopoietic cell transplant patients when used as cytomegalovirus prophylaxis 5

Cidofovir

• Currently the only licensed antiviral under restricted IND protocol for orthopoxvirus infections 1
• Reserved as second-line therapy due to nephrotoxicity and lack of oral bioavailability 1
• May only be administered when vaccinia immune globulin is not efficacious 1

Management of Vaccine Complications (Not Smallpox Disease)

Vaccinia Immune Globulin (VIG)

• VIG has no role in treating smallpox disease itself 1
• Reserved exclusively for severe vaccine complications: progressive vaccinia, eczema vaccinatum, and severe generalized vaccinia 1
• Dosing for complications: 0.6 mL/kg intramuscularly, administered in divided doses over 24-36 hours 1
• VIG is contraindicated for vaccinial keratitis 1
• Current supplies are extremely limited 1

Key Clinical Distinctions

It is critical to distinguish between:

• Smallpox disease treatment (supportive care only, no proven effective therapies) 1
• Post-exposure prophylaxis (vaccination within 3-4 days) 1
• Vaccine complication management (VIG for specific severe reactions) 1
• Investigational antivirals (tecovirimat and brincidofovir approved under Animal Rule but not yet proven in human smallpox) 5, 2, 3

Common Pitfalls

• Do not confuse vaccine adverse reaction treatments (VIG, cidofovir) with treatments for actual smallpox disease 1
• VIG provides no benefit for smallpox disease and should never be used for this indication 1
• The investigational antivirals (tecovirimat, brincidofovir) were approved based on animal models, not human smallpox cases, as clinical trials in natural disease are impossible 3
• Isolation must continue until all scabs separate, not just until fever resolves 1