infectious diseases
Smallpox
Prevention of Smallpox
Licensed smallpox vaccines in the United States consist of ACAM2000, a live replication-competent vaccinia virus and JYNNEOS, a live attenuated (replication-deficient) modified vaccinia Ankara (MVA) vaccine ( Prevention references ). This attenuated (weakened) vaccine does not reproduce in the person who receives it. (See also Vaccinia virus is related to smallpox and provides cross-immunity. ACAM2000 vaccine is administered with a bifurcated needle dipped in reconstituted vaccine. The needle is rapidly jabbed 15 times in an area about 5 mm in diameter and with sufficient force to draw a trace of blood. The vaccine site is covered with a dressing to prevent spread of the vaccine virus to other body sites or to close contacts. Fever, malaise, and myalgias are common the week after vaccination. Successful vaccination is indicated by development of a pustule by about the 7th day. People without such signs of successful vaccination should be given another dose of vaccine. Vaccination with ACAM2000 is dangerous and not recommended for some people, especially those with the following risk factors: Weakened immune system (such as those who have AIDS or who take medications that suppress the immune system) Skin disorders (particularly atopic dermatitis [eczema]) Eye inflammation Heart condition Age under 1 year Pregnancy JYNNEOS is administered as 2 subcutaneous injections 4 weeks apart. It is licensed by the FDA for people 18 years of age and older. The JYNNEOS vaccine may have a particular role in vaccinating people for whom ACAM2000 may be contraindicated, such as those with immunocompromised states or atopic dermatitis (see above list). However, people who have a weakened immune system may have a diminished response the JYNNEOS vaccine. Another live virus investigational vaccine Aventis Pasteursmallpox vaccine(APSV) is also available from the Strategic National Stockpile in the event of an emergency. After a single vaccination, immunity begins to fade after 5 years and is probably negligible after 20 years. If people have been successfully revaccinated one or more times, some residual immunity may persist for ≥ 30 years. Until an outbreak in the population occurs, preexposure vaccination remains recommended only for people at high risk of exposure to the virus (eg, laboratory technicians [ Prevention references ]). Progressive vaccinia is a nonhealing vesicular lesion that develops after smallpox vaccination and spreads broadly to involve skin other than the immunization site and deeply to involve bones and viscera. It occurs almost exclusively in vaccine recipients with an underlying defect in cell-mediated immunity. Image courtesy of Dr. Allen W. Mathies of the Immunization Branch of the California Emergency Preparedness Office (Calif/EPO) via the Public Health Image Library of the Centers for Disease Control and Prevention. Progressive vaccinia is a nonhealing vesicular lesion that develops after smallpox vaccination and spreads broadly to involve skin other than the immunization site and deeply to involve bones and viscera. It occurs almost exclusively in vaccine recipients with an underlying defect in cell-mediated immunity. Image courtesy of Dr. Allen W. Mathies of the Immunization Branch of the California Emergency Preparedness Office (Calif/EPO) via the Public Health Image Library of the Centers for Disease Control and Prevention. Eczema vaccinatum is vaccinia that develops in patients with eczematous skin. Active eczema may not be clinically apparent in affected sites. Patients may develop eczema vaccinatum after receiving the vaccine themselves or from physical contact with someone who received the vaccine. Image courtesy of Arthur E. Kaye via the Public Health Image Library of the Centers for Disease Control and Prevention. Generalized vaccinia is diffusely distributed vaccinial lesions caused by hematogenous spread of the vaccinia virus after vaccination. Despite a possibly severe appearance, generalized vaccinia is usually benign. Image courtesy of Dr. Allen W. Mathies of the Immunization Branch of the California Emergency Preparedness Office (Calif/EPO) via the Public Health Image Library of the Centers for Disease Control and Prevention. Risk factors for complications of the replication-competent virus vaccine (ACAM2000) include extensive skin disorders (particularly eczema), immunosuppressive diseases or therapies, ocular inflammation, pregnancy, heart conditions, and age under 1 year. Widespread vaccination is not recommended because of the risk. Serious complications occur in about 1 of 10,000 patients after their first (primary) vaccination and include Postvaccinial encephalitis Progressive vaccinia Eczema vaccinatum Generalized vaccinia Myocarditis and/or pericarditis Vaccinia virus keratitis Noninfectious rashes Postvaccinial encephalitisoccurs in about 1 of 300,000 recipients of primary vaccination, typically 8 to 15 days postvaccination. Progressive vaccinia(vaccinia necrosum) results in a nonhealing vaccinial (vesicular) skin lesion that spreads to adjacent skin and ultimately other skin areas, bones, and viscera. Progressive vaccinia may occur after primary vaccination or revaccination but occurs almost exclusively in patients with an underlying defect in cell-mediated immunity; it can be fatal. Eczema vaccinatumresults in vaccinial skin lesions appearing on areas of active or even healed eczema. Generalized vacciniaresults from hematogenous dissemination of the vaccinia virus and causes vaccinia lesions at multiple body locations; it is usually benign. Vaccinia virus keratitisoccurs rarely, when vaccinia virus is inadvertently implanted in the eye. Some serious vaccine complications are treated withvaccinia immune globulin(VIG); one case of eczema vaccinatum apparently treated successfully with VIG,cidofovir, andtecovirimathas been reported. In the past, high-risk patients who required vaccination because of viral exposure were simultaneously given VIG to try to prevent complications. The efficacy of this practice is unknown, and it is not recommended by the CDC. VIG is available only from the CDC. Postexposure vaccination with a replication-competent vaccine can prevent or significantly limit the severity of illness and is indicated for family members and close personal contacts of smallpox patients. Early administration is most effective, but some benefit is realized up to 7 days postexposure. 1.Pittman PR, Hahn M, Lee HS, et al: Phase 3 efficacy trial of modified vaccinia ankara as a vaccine against smallpox.N Engl J Med381(20):1897-1908, 2019. doi: 10.1056/NEJMoa1817307 2.Petersen BW, Harms TJ, Reynolds MG, et al: Use of vaccinia virussmallpox vaccinein laboratory and health care personnel at risk for occupational exposure to orthopoxviruses: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2015.MMWR Morb Mortal Wkly Rep65 (10):257–262, 2016. doi: 10.15585/mmwr.mm6510a2 