Interferon α/ß Decoy Receptor Encoded by a Variant in the Dryvax Smallpox Vaccine Contributes to Virulence and Correlates with Severe Vaccine Side Effects.

Although providing long-lasting immunity, smallpox vaccination was associated with local and systemic reactions and rarely with severe complications, including progressive vaccinia and postvaccinia encephalitis. As the Dryvax smallpox vaccine consists of a population of variants, we investigated a particularly pathogenic isolate called clone 3 (CL3). Virus replication was monitored by inserting the gene encoding firefly luciferase (Luc) into the genomes of CL3 and ACAM2000, the second-generation smallpox vaccine derived from a less virulent clone. Greater luminescence occurred following intranasal or intraperitoneal inoculation of mice with CL3-Luc than ACAM2000-Luc. Previous genome sequencing of CL3 and ACAM2000 revealed numerous differences that could affect pathogenicity. We focused on a 4.2-kbp segment, containing several open reading frames, in CL3 that is absent from ACAM2000 and determined that lower virulence of the latter was associated with a truncation of the interferon α/ß (IFN-α/ß) decoy receptor. Truncation of the decoy receptor in CL3-Luc and repair of the truncated version in ACAM2000-Luc decreased and increased virulence, respectively. Blockade of the mouse type 1 IFN receptor increased the virulence of ACAM2000-Luc to that of CL3-Luc, consistent with the role of IFN in attenuating the former. The severities of disease following intracranial inoculation of immunocompetent mice and intraperitoneal inoculation of T cell-depleted mice were also greater in viruses expressing the full-length decoy receptor. Previous evidence for the low affinity of a similarly truncated decoy receptor for IFN and the presence of a full-length decoy receptor in virus isolated from a patient with progressive vaccinia support our findings. IMPORTANCE Attenuated live viruses make effective vaccines, although concerns exist due to infrequent complications, particularly in individuals with immunological defects. Such complications occurred with smallpox vaccines, which were shown to be comprised of populations of variants. Clone 3, isolated from Dryvax, the vaccine most widely used in the United States during the smallpox eradication campaign, was particularly pathogenic in animal models. We demonstrated that the full-length IFN-α/ß decoy receptor in CL3 and a truncation of the receptor in the clone used for the second-generation smallpox vaccine ACAM2000 account for their difference in pathogenicity. Viruses expressing the full-length decoy receptor were more virulent following intranasal, intraperitoneal, or intracranial inoculation of mice than ACAM2000, and disease was exacerbated following T cell depletion. Correspondingly, the full-length decoy receptor is present in smallpox vaccines with high rates of side effects and in a Dryvax clone obtained from a lesion in a patient with progressive vaccinia.

Safety and Immunogenicity of Heterologous and Homologous 2-Dose Regimens of Adenovirus Serotype 26- and Modified Vaccinia Ankara-Vectored Ebola Vaccines: A Randomized, Controlled Phase 1 Study.

BACKGROUND: This phase 1 placebo-controlled study assessed the safety and immunogenicity of 2-dose regimens of Ad26.ZEBOV (adenovirus serotype 26 [Ad26]) and MVA-BN-Filo (modified vaccinia Ankara [MVA]) vaccines with booster vaccination at day 360. METHODS: Healthy US adults (N = 164) randomized into 10 groups received saline placebo or standard or high doses of Ad26 or MVA in 2-dose regimens at 7-, 14-, 28-, or 56-day intervals; 8 groups received booster Ad26 or MVA vaccinations on day 360. Participants reported solicited and unsolicited reactogenicity; we measured immunoglobulin G binding, neutralizing antibodies and cellular immune responses to Ebola virus glycoprotein. RESULTS: All regimens were well tolerated with no serious vaccine-related adverse events. Heterologous (Ad26,MVA [dose 1, dose 2] or MVA,Ad26) and homologous (Ad26,Ad26) regimens induced humoral and cellular immune responses 21 days after dose 2; responses were higher after heterologous regimens. Booster vaccination elicited anamnestic responses in all participants. CONCLUSIONS: Both heterologous and homologous Ad26,MVA Ebola vaccine regimens are well tolerated in healthy adults, regardless of interval or dose level. Heterologous 2-dose Ad26,MVA regimens containing an Ebola virus insert induce strong, durable humoral and cellular immune responses. Immunological memory was rapidly recalled by booster vaccination, suggesting that Ad26 booster doses could be considered for individuals at risk of Ebola infection, who previously received the 2-dose regimen.

Adverse events following smallpox vaccination with ACAM2000 in a military population.

BACKGROUND: Generalized vaccinia and benign exanthems are 2 adverse events that have been associated with the smallpox vaccination. Accurate incidence and prevalence rates of each are not readily available, but these events are thought to be uncommon. To our knowledge, this is the first case series to provide clinical as well as pathologic descriptions of multiple papulovesicular eruptions occurring after receiving the second-generation smallpox vaccine, ACAM2000 (Acambis, Canton, Massachusetts), among a vaccinia-naïve military population. In addition, we report the first confirmed case, to our knowledge, of generalized vaccinia following administration of the ACAM2000 vaccine. OBSERVATIONS: All patients received primary smallpox immunization as well as 1 to 3 concurrent or near-concurrent (within the preceding 21 days) immunizations for typhoid, anthrax, hepatitis B, and/or seasonal influenza. One patient presented with a flulike prodrome and diffuse vesiclopustules covering the face, neck, chest, back, and upper and lower extremities. Vaccinia polymerase chain reaction confirmed generalized vaccinia. The remaining 7 patients presented with unusual, painful, and pruritic papulovesicular eruptions occurring on the extensor surfaces of their upper and lower extremities without systemic symptoms. Histologic findings revealed 2 general patterns, including a dermal hypersensitivity reaction with lymphocytic vasculitis and a vesicular spongiotic dermatitis with eosinophils. CONCLUSIONS: We present the first confirmed case of generalized vaccinia following immunization with the second-generation smallpox vaccine ACAM2000. In addition, we describe 7 cases of benign, acral, papulovesicular eruptions thought to be associated with ACAM2000 administration. Further research is needed to discern the pathogenesis of these benign eruptions as well as their incidence and prevalence and that of generalized vaccinia with ACAM2000.

A population survey of smallpox knowledge, perceptions, and healthcare-seeking behavior surrounding the Iraq invasion--Connecticut 2002-03.

BACKGROUND: Knowledge and perceptions about smallpox would probably influence public behavior following an intentional smallpox release. We assessed public knowledge, perceptions, and related healthcare-seeking behavior in Connecticut during the period of heightened interest in smallpox preparedness surrounding the Iraq invasion. METHODS: Smallpox-related questions were added to Connecticut's Behavioral Risk Factor Surveillance System survey, an ongoing statewide adult population-based survey during December 2002-July 2003 and November-December 2003. RESULTS: Among 4,074 respondents, when asked about a hypothetical febrile illness, 72% would first contact their primary care provider (PCP) on weekdays. During nights and weekends, respondents would depend nearly equally on PCPs and emergency departments (37% versus 36%). Most knew smallpox is transmissible from person to person (72%) but not that the majority infected with smallpox survive (38%) or that smallpox is most contagious after the appearance of rash (11%). Knowledge regarding transmissibility and mortality improved during the study period (p < 0.001). Only 31% recognized that vaccinia vaccine is riskier than routine vaccines; 41% would choose vaccination if available. Concern about smallpox's potential use as a weapon was high but decreased after President Bush declared "mission accomplished" in Iraq in May 2003 (p < 0.001). CONCLUSIONS: Despite national coverage of smallpox by the media, most respondents lacked basic knowledge regarding the disease. Incorrect perceptions regarding vaccinia vaccine's risks could increase inappropriate vaccine demand among nonexposed people with vaccine contraindications during a mass vaccination campaign. Current perceptions should inform future smallpox preparedness planning. In addition, both PCPs and emergency medicine clinicians should be targeted for education regarding smallpox diagnosis.

Lack of vaccinia viremia after smallpox vaccination.

Although the transmission of certain viral infections (human immunodeficiency virus, hepatitis B and C viruses, and West Nile virus) through donated blood products is well described, the risk of transmitting vaccinia virus after smallpox vaccination is unknown. Blood samples from patients receiving the smallpox vaccine were obtained before vaccination; then from one-half of the study group on alternate days for each of the first 10 days after vaccination; then from all patients on days 14 and 21 after vaccination. Samples were analyzed by culture, polymerase chain reaction, and antigen detection (electrochemiluminescence) assay for the presence of vaccinia virus. Two hundred and twenty samples from 28 volunteers were processed by all 3 laboratory detection methods and all were negative for the presence of vaccinia virus (confidence interval, 0%-12.3%). Viremia with vaccinia virus after smallpox vaccination appears to be an uncommon occurrence.

Risks of serious complications and death from smallpox vaccination: a systematic review of the United States experience, 1963-1968.

BACKGROUND: The United States (US) has re-instituted smallpox vaccinations to prepare for an intentional release of the smallpox virus into the civilian population. In an outbreak, people of all ages will be vaccinated. To prepare for the impact of large-scale ring and mass vaccinations, we conducted a systematic review of the complication and mortality risks of smallpox vaccination. We summarized these risks for post-vaccinial encephalitis, vaccinia necrosum (progressive vaccinia), eczema vaccinatum, generalized vaccinia, and accidental infection (inadvertant autoinoculation). METHODS: Using a MEDLINE search strategy, we identified 348 articles, of which seven studies met our inclusion criteria (the number of primary vaccinations and re-vaccinations were reported, sufficient data were provided to calculate complication or case-fatality risks, and comparable case definitions were used). For each complication, we estimated of the complication, death, and case-fatality risks. RESULTS: The life-threatening complications of post-vaccinial encephalitis and vaccinia necrosum were at least 3 and 1 per million primary vaccinations, respectively. Twenty-nine percent of vaccinees with post-vaccinial encephalitis died and 15% with vaccinia necrosum died. There were no deaths among vaccinees that developed eczema vaccinatum; however, 2.3% of non-vaccinated contacts with eczema vaccinatum died. Among re-vaccinees, the risk of post-vaccinial encephalitis was reduced 26-fold, the risk of generalized vaccinia was reduced 29-fold, and the risk of eczema vaccinatum was reduced 12-fold. However, the risk reductions of accidental infection and vaccinia necrosum were modest (3.8 and 1.5 fold respectively).

Smallpox vaccination: a review, part II. Adverse events.

Smallpox vaccination of health care workers, military personnel, and some first responders has begun in the United States in 2002-2003 as one aspect of biopreparedness. Full understanding of the spectrum of adverse events and of their cause, frequency, identification, prevention, and treatment is imperative. This article describes known and suspected adverse events occurring after smallpox vaccination.

Transmission of vaccinia virus and rationale for measures for prevention.

Currently, health care workers (HCWs) in the United States are being vaccinated against smallpox, and there is a possibility that this will be expanded to a more widespread vaccination program. Inadvertent transmission of vaccinia virus to patients with illnesses that are contraindications to vaccination is theoretically possible. Vaccinia virus is shed from the vaccination lesion of healthy primary vaccinees from approximately the third day to the end of the third week after vaccination; transmission of vaccinia virus is rare but does occur. Prudent management of the vaccination site by HCWs should virtually eliminate transmission. We recommend that vaccinated HCWs cover the site with loose gauze dressings and, when caring for patients with immunosuppression or extensive disruptive skin disorders, cover the dressings with semipermeable membranes. The evidence for respiratory spread of vaccinia virus is not compelling, and therefore droplet or airborne infection precautions should not be necessary, even for vaccinated HCWs who are caring for patients who experienced serious adverse events after smallpox vaccination in the past.