Smallpox vaccination in 2003: key information for clinicians

From ancient remedies to modern miracles: tracing the evolution of vaccines and their impact on public health

This review traces the development of vaccines from ancient times to the present, highlighting major milestones and challenges. It covers the significant impact of vaccines on public health, including the eradication of diseases such as smallpox and the reduction of others such as polio, measles, and influenza. The review provides an in-depth look at the COVID-19 vaccines, which were developed at unprecedented speeds due to the urgent global need. The study emphasizes the ongoing potential of vaccine development to address future global health challenges, demonstrating the critical role vaccines play in disease prevention and public health. Moreover, it discusses the evolution of vaccine technology, from live-attenuated and inactivated vaccines to modern recombinant and mRNA vaccines, showcasing the advancements that have enabled rapid responses to emerging infectious diseases. The review underscores the importance of continued investment in research and development, global collaboration, and the adoption of new technologies to enhance vaccine efficacy and coverage. By exploring historical and contemporary examples, the article illustrates how vaccines have transformed medical practice and public health outcomes, providing valuable insights into future directions for vaccine innovation and deployment.

Comprehensive literature review of monkeypox

The current outbreak of monkeypox (MPX) infection has emerged as a global matter of concern in the last few months. MPX is a zoonosis caused by the MPX virus (MPXV), which is one of the Orthopoxvirus species. Thus, it is similar to smallpox caused by the variola virus, and smallpox vaccines and drugs have been shown to be protective against MPX. Although MPX is not a new disease and is rarely fatal, the current multi-country MPX outbreak is unusual because it is occurring in countries that are not endemic for MPXV. In this work, we reviewed the extensive literature available on MPXV to summarize the available data on the major biological, clinical and epidemiological aspects of the virus and the important scientific findings. This review may be helpful in raising awareness of MPXV transmission, symptoms and signs, prevention and protective measures. It may also be of interest as a basis for performance of studies to further understand MPXV, with the goal of combating the current outbreak and boosting healthcare services and hygiene practices.Trial registration: ClinicalTrials.gov identifier: NCT02977715..Trial registration: ClinicalTrials.gov identifier: NCT03745131..Trial registration: ClinicalTrials.gov identifier: NCT00728689..Trial registration: ClinicalTrials.gov identifier: NCT02080767..

Axillary lymphadenopathy in a renal cell carcinoma patient after COVID-19 Vaccination

The distribution of the novel Covid-19 vaccines has been on a scale as unprecedented as the pandemic itself. While the vaccines promise to greatly reduce the spread and impact of the disease, encountering side-effects in clinical practice may pose diagnostic dilemmas. In this case report, we describe a patient with known metastatic renal cell carcinoma who presents with axillary lymphadenopathy found on PET/CT imaging after receiving a Covid-19 vaccine, which was subsequently confirmed to be reactive lymphadenopathy following biopsy.

Neurologic Manifestations of the World Health Organization's List of Pandemic and Epidemic Diseases

The World Health Organization (WHO) monitors the spread of diseases globally and maintains a list of diseases with epidemic or pandemic potential. Currently listed diseases include Chikungunya, cholera, Crimean-Congo hemorrhagic fever, Ebola virus disease, Hendra virus infection, influenza, Lassa fever, Marburg virus disease, Neisseria meningitis, MERS-CoV, monkeypox, Nipah virus infection, novel coronavirus (COVID-19), plague, Rift Valley fever, SARS, smallpox, tularemia, yellow fever, and Zika virus disease. The associated pathogens are increasingly important on the global stage. The majority of these diseases have neurological manifestations. Those with less frequent neurological manifestations may also have important consequences. This is highlighted now in particular through the ongoing COVID-19 pandemic and reinforces that pathogens with the potential to spread rapidly and widely, in spite of concerted global efforts, may affect the nervous system. We searched the scientific literature, dating from 1934 to August 2020, to compile data on the cause, epidemiology, clinical presentation, neuroimaging features, and treatment of each of the diseases of epidemic or pandemic potential as viewed through a neurologist's lens. We included articles with an abstract or full text in English in this topical and scoping review. Diseases with epidemic and pandemic potential can be spread directly from human to human, animal to human, via mosquitoes or other insects, or via environmental contamination. Manifestations include central neurologic conditions (meningitis, encephalitis, intraparenchymal hemorrhage, seizures), peripheral and cranial nerve syndromes (sensory neuropathy, sensorineural hearing loss, ophthalmoplegia), post-infectious syndromes (acute inflammatory polyneuropathy), and congenital syndromes (fetal microcephaly), among others. Some diseases have not been well-characterized from a neurological standpoint, but all have at least scattered case reports of neurological features. Some of the diseases have curative treatments available while in other cases, supportive care remains the only management option. Regardless of the pathogen, prompt, and aggressive measures to control the spread of these agents are the most important factors in lowering the overall morbidity and mortality they can cause.

Treatment of neuroterrorism

Bioterrorism is defined as the intentional use of biological, chemical, nuclear, or radiological agents to cause disease, death, or environmental damage. Early recognition of a bioterrorist attack is of utmost importance to minimize casualties and initiate appropriate therapy. The range of agents that could potentially be used as weapons is wide, however, only a few of these agents have all the characteristics making them ideal for that purpose. Many of the chemical and biological weapons can cause neurological symptoms and damage the nervous system in varying degrees. Therefore, preparedness among neurologists is important. The main challenge is to be cognizant of the clinical syndromes and to be able to differentiate diseases caused by bioterrorism from naturally occurring disorders. This review provides an overview of the biological and chemical warfare agents, with a focus on neurological manifestation and an approach to treatment from a perspective of neurological critical care.

Demographic and clinical factors associated with response to smallpox vaccine in preimmunized volunteers

Context

In March 2003, the French Ministry of Health implemented a program on preparedness and response to a biological attack using smallpox as weapon. This program included the establishment of a preoutbreak national team that could be revaccinated against smallpox.

Objective

To identify demographic and clinical factors associated with vaccination success defined as the presence of a pustule at the inoculation site at day 8 (days 7–9), with an undiluted vaccinia virus derived from a Lister strain among preimmunized volunteers.

Volunteers and Methods

From March 2003 to November 2006, we have studied prospectively 226 eligible volunteers. Demographic data were recorded for each volunteer (age, sex, number of previously smallpox vaccinations and date of the last vaccination). Smallpox vaccine adverse reactions were diagnosed on the basis of clinical examination performed at days 0, 7, 14, 21 and 28 after revaccination.

Results

A total of 226 volunteers (sex ratio H/F = 2.7) were revaccinated. Median age was 45 years (range: 27–63 yrs). All volunteers completed follow-up. Median number of vaccinations before revaccination was 2 (range: 1–8). The median delay between time of the study and the last vaccination was 29 years (range; 18–60 yrs). Sixty-one volunteers (27%) experienced one (n = 40) or more (n = 21) minor side effects during the 2–14 days after revaccination. Successful vaccination was noted in 216/226 volunteers (95.6%) at day 8 and the median of the pustule diameter was 5 mm (range: 1–20 mm). Size of the pustule at day 8 was correlated with age (p = 0.03) and with the presence of axillary adenopathy after revaccination (p = 0.007). Sex, number of prior vaccinations, delay between the last vaccination and revaccination, and local or systemic side effects with the exception of axillary adenopathy, were not correlated with the size of the pustule at day 8.

Conclusions

Previously vaccinated volunteers can be successfully revaccinated with the Lister strain.

Biological terrorism

A biological terrorism event could have a large impact on the general population and health care system. The impact of an infectious disaster will most likely be great to emergency departments, and the collaboration between emergency and infectious disease specialists will be critical in developing an effective response. A bioterrorism event is a disaster that requires specific preparations beyond the usual medical disaster planning. An effective response would include attention to infection control issues and plans for large-scale vaccination or antimicrobial prophylaxis. This article addresses some general issues related to preparing an effective response to a biological terrorism event. It will also review organisms and toxins that could be used in biological terrorism, including clinical features, management, diagnostic testing, and infection control.

The smallpox vaccine

BACKGROUND

A heightened awareness of the potential for bioterrorist attacks in the United States has led to the expansion of the nation's supply of smallpox vaccine and the institution of procedures to distribute this vaccine in the unlikely event of a release of this potentially deadly agent.

METHODS

The authors conducted a review of the relevant smallpox literature through a MEDLINE search. They also reviewed the Web site of the Centers for Disease Control and Prevention and numerous other Web sites.

RESULTS

The authors considered for inclusion more than 100 articles discussing smallpox, the smallpox vaccine and the role of the dental professional in a bioterrorist attack.

CONCLUSIONS

Dentists may detect the initial signs of a smallpox infection, provide information concerning the disease to the public and potentially assist in the administration of smallpox vaccine.

CLINICAL IMPLICATIONS

Should an intentional release of smallpox occur, the dental professional may play an important role in its treatment and prevention.

Clinical and immunological comparison of smallpox vaccine administered to the outer versus the inner upper arms of vaccinia-naive adults

BACKGROUND

Current recommendations direct health care providers to administer smallpox vaccine to the upper outer arm. However, concerns about cosmetically bothersome scarring, accidental contact transmission, interference by body tattoos, and even malignant transformation suggest evaluation of alternate vaccination sites is warranted.

METHODS

We randomized 20 vaccinia-naive adults to undergo smallpox vaccination on the outer (n = 10) or inner (n = 10) upper arm. Evaluations included major reaction ("take") rates and vaccination site cultures on postvaccination day 7, determination of serum vaccinia-specific neutralizing antibody titers on days 0 (prevaccination) and 21, and determination of adverse events.

RESULTS

On postvaccination day 7, a total of 18 participants (9 per group) had major reactions, 17 of whom had culture evidence of viable vaccinia. The inner and outer arm groups had similar major reaction mean sizes (P = .17), but the amount of erythema (in square centimeters) was smaller in the inner arm group (P = .05). At day 21, all participants had higher titers of vaccinia-specific neutralizing antibodies, compared with at day 0, and the geometric mean titer values of the 2 vaccine groups were similar (P = .45). Adverse event rates were similar.

CONCLUSION

The comparable clinical, immunological, and tolerability outcomes between smallpox vaccine applied to the conventional upper outer arm site versus the upper inner arm, coupled with modestly less vaccine-site erythema on the inner arm, indicate that the inner arm may be a suitable alternate vaccination site.

Persisting humoral antiviral immunity within the Japanese population after the discontinuation in 1976 of routine smallpox vaccinations

Concerns have arisen recently about the possible use of smallpox for a bioterrorism attack. Routine smallpox vaccination was discontinued in Japan in 1976; however, it is uncertain exactly how long vaccination-induced immunity lasts. We sought to evaluate the seroprevalence and intensity of anti-smallpox immunity among representatives of the present Japanese population. The subjects included 876 individuals who were born between 1937 and 1982. Vaccinia virus-specific immunoglobulin G (IgG) levels were measured by enzyme-linked immunosorbent assay (ELISA), and 152 of 876 samples were also tested for the presence of neutralizing antibodies. Of the subjects who were born before 1962, between 1962 and 1968, and between 1969 and 1975, 98.6, 98.6, and 66.0%, respectively, still retained the vaccinia virus-specific IgG with ELISA values for optical density at 405 nm (OD(405)) of > or = 0.10. The corresponding figures for retained IgGs with OD405 values of > or = 0.30 were 91.0, 90.3, and 58.2%, respectively. Neutralizing antibodies were also maintained. The sera with OD(405) values of > or = 0.30 showed 89% sensitivity and a 93% positive predictive value for detection of neutralizing antibodies (> or = 4). Thus, approximately 80% of persons born before 1969 and 50% of those born between 1969 and 1975 were also found to have maintained neutralizing antibodies against smallpox. A considerable proportion of the previous vaccinated individuals still retain significant levels of antiviral immunity. This long-lasting immunity may provide some protective benefits in the case of reemergence of smallpox, and the disease may not spread as widely and fatally as generally expected.

Bioterrorism: Preparing for the impossible or the improbable

OBJECTIVE

To review the current literature surrounding the history of bioterrorism, the relative risk of a bioterrorist attack, methods of surveillance for biological agents, identification and management of various biological agent casualties, as well as the role of the intensivist in managing a bioterrorist attack.

METHODS

Internet and Medline search (from 1966 to 2004) for articles relating to bioterrorism, biological agents, biological warfare, hospital preparedness, disaster management, and intensive care.

CONCLUSIONS

There are few instances of a successful large-scale biological weapons attack in history. Weaponization of biological agents for aerosol dispersal is difficult and has often proved to be the rate-limiting step for a successful attack. Although a successful biological attack is currently unlikely, it is still feasible. More importantly, the threat of one is likely to cause much panic in the public, while a successful attack would overburden the current healthcare infrastructure. Intensivists will need to have specific knowledge of identifying and managing casualties from various biological agents. In addition, they will need to play an integral part in the preparedness of their institutions and communities for managing a bioterrorist event.

Risque de variole, vaccination et bioterrorisme

The use of the smallpox virus as a biological weapon is very old. Confronted with a high probability of a current bioterrorist menace, counteracting strategies have been developed. One of the principle aims relies on the vaccination of teams dedicated to the management of persons infected and the stocking of vaccine for the whole population of a country. Following worldwide eradication of the disease, preventive vaccination was topped in 1978 in France for the primo-vaccination, and in 1984 for repeat vaccinations. The various strains used in the first generation vaccinations are weakened living vaccine, the natural host and origin of which is unknown. Second and third generations vaccines are under study; the principle objective is to obtain efficacy with a minimum of side effects. There are two types of adverse events, generally observed with the first generation vaccines: the first, extremely rare, can be life-threatening; the others, more frequent (10 to 15% of patients) are benign. In emergency situations, in the presence of smallpox, there should be no absolute contraindications to vaccination. In the bioterrorist context, massive vaccination campaigns of the population are unadvisable (because of the considerable risk of death and severe adverse events) in the absence of any real permit, in each case, definition of the vaccinal strategy to be adopted.

[Update on smallpox vaccines]

Smallpox is among the most dangerous pathogens that could be used by bioterrorists. The former vaccines produced by scarification on the flanks of calves or sheep could be used to protect the whole French population when used with bifurcated needles. They should be replaced by a second-generation vaccine grown in cell culture and, eventually later by new and safer third-generation vaccines using non-replicative viral strains.

Smallpox in the 21st century

The viral disease, smallpox, was well known through the end of the 20th Century. Because it has been eradicated from natural populations, the present clinical experience with managing the disease is limited. Similarly, research in the pathophysiology, treatment, and prevention of the disease has recently become a priority. Concerns regarding smallpox as a weapon of bioterrorism have led to the implementation of a new prophylactic vaccine program, a renewal in variola vaccine research, and treatment regimens against variola infection.

Randomized Trial Comparing Vaccinia on the External Surfaces of 3 Conventional Bandages Applied to Smallpox Vaccination Sites in Primary Vaccinees

BACKGROUND

Concern about accidental contact transmission after smallpox vaccination has prompted various recommendations regarding vaccination site coverage.

METHODS

On days 6-8 after their first-ever smallpox vaccination, 63 adult subjects were randomized to apply a self-adhesive bandage (n=20), gauze with adhesive tape (n=21), or gauze with a semipermeable dressing (n=22) over the vaccination site for a mean of 8+/-2 h. Swabs from the external bandage surfaces and the vaccination sites were then assessed by real time vaccinia-specific polymerase chain reaction (PCR) in blinded fashion.

RESULTS

Among 58 subjects completing the study, PCR results were positive for the vaccination site in 55 (94.8%) and on 10 swabs (17.2%) from external bandage surfaces. There were no differences among the 3 bandages (P=.57).

CONCLUSIONS

At 7 days after smallpox vaccination, a peak time for vaccinia shedding, a self-adhesive bandage was as effective as 2 bulkier, less convenient bandages in limiting PCR-detectable virus on the external surface.

Anticipating smallpox and monkeypox outbreaks: complications of the smallpox vaccine

BACKGROUND

The recent outbreak in the Midwest of monkeypox, as well as the continued fears of a terrorist-induced epidemic of smallpox, prompted the authors' review of the literature regarding past and current experiences with smallpox vaccination. The smallpox vaccine, which is highly effective in preventing the spread of both these orthopoxvirus infectious illnesses, might be administered to numerous health care workers and, in the event of a smallpox attack, millions of other citizens. However, vaccinees would be at risk for several vaccine-related neurologic complications.

REVIEW SUMMARY

According to prior reports, neurologic complications have occurred in 2.5 per million US individuals, with the most common being postvaccinal encephalomyelitis (PVEM). In older children and adults, PVEM causes stupor and coma, seizures, paraparesis, and other neurologic and mental abnormalities, and, in 16% of cases, permanent neurologic sequelae. The overall mortality rate of neurologic complications is approximately 1.5 per million vaccinees. Risk factors for PVEM were age younger than 1 year and no previous smallpox vaccination, but not a prior episode of PVEM or other preexisting neurologic illnesses. Neither the current smallpox vaccination campaigns in Israel nor the one in the United States has had comparable complications, but the US campaign has been associated with myocarditis and myopericarditis.

CONCLUSION

Although the potential neurologic complications of the smallpox vaccine must be weighed against the threat of monkeypox and smallpox, current experience with vaccination suggests it carries a very low risk of neurologic complications and does not lead to exacerbations of chronic neurologic illnesses.

Smallpox: vaccine reactions and contraindications

Concern regarding the use of smallpox for bioterrorism has led to the reintroduction of smallpox vaccination. The historic background leading to protective methods against smallpox disease, the adverse reactions and contraindications associated with vaccination, and the ongoing development of potentially safer smallpox vaccines are reviewed here.

Triage of a febrile patient with a rash: a comparison of chickenpox, monkeypox, and smallpox

The immediate and correct recognition of an infectious exanthema can be aided with a focused history and minor assessment. False alarms can consume health care resources and create unnecessary anxiety. Clinicians can use specific references to not only help with educating staff, but to ensure a more accurate diagnosis and trigger notification of appropriate infectious disease protocols. The authors recommend that al emergency departments have a process in place to immediately isolate suspicious cases until a more thorough medial workup can be performed.

Vaccines for the prevention of diseases caused by potential bioweapons

The development of vaccines and implementation of vaccination programs are among the most important medical contributions to humanity. To date, vaccination has reduced morbidity and mortality from infectious diseases more than any other specific medical intervention. The intentional use of bioweapons against civilians (bioterrorism), recently highlighted by events around the world, has fueled interest in the development of vaccines for potential microbial agents of bioterror. This review discusses the microbial agents that are considered to pose the greatest risk to the public, the diseases associated with them, and the vaccines that are available for their prevention. The paucity of such vaccines and uncertainty regarding mechanisms of vaccine efficacy and the microbial antigens that elicit protection underscore the need for continued study of host-microbe interaction and the immune response to potential agents of bioterror for the development of new vaccines and immune-based therapies to combat their potential to harm the public.

Bioterrorism and the nervous system

Recent events of war, terrorist attacks, and mail-borne anthrax exposure have produced increasing awareness of potential bioterrorism attacks in the United States and other parts of the world. Physicians and healthcare personnel play a key role in identifying potential bioterrorist attacks. Early recognition and preparedness for bioterrorism-associated illnesses is especially important for neurologists because most bioterrorism agents can directly or indirectly affect the nervous system. This article reviews the neurologic manifestations, diagnosis, and treatments of syndromes caused by potential bioterrorism agents, as well as the potential side effects of vaccines against some of these agents.

Smallpox vaccine: problems and prospects

Smallpox justifiably is feared because of its morbidity and mortality. Wide-spread population-level susceptibility to smallpox exists, and the only effective tool against the virus is a live, attenuated vaccine that is highly reactogenic and controversial. A significant minority of the population has contraindications that prevent preexposure use of this vaccine. Newer, safer, and equally immunogenic vaccines must be developed and licensed. Several live, attenuated vaccines are in clinical trials. Although these vaccines may prove to be less reactogenic, they still may not be administered safely to a significant portion of the population because they contain live, attenuated viruses. Newer vaccines will be needed if routine preexposure vaccination is to be instituted universally. The idea of a subunit or peptide-based vaccine is appealing, because it obviates potential safety concerns. It may be possible to use a more-attenuated, live vaccine strain for a large segment of the population on a preexposure basis and accept the morbidity and mortality that would result from its use on a postexposure basis, if necessary. The need for widespread population-level protection against variola infection is apparent. The use of the new biology tools to predict or define who might experience serious reactions to the smallpox vaccine and why these reactions occur is an area ripe for additional research. The reason why an individual develops postvaccinal encephalitis remains unknown, and the development is unpredictable and untreatable. In the future, if the mechanism behind such adverse events is defined, it may be possible to screen persons who are likely to experience such events. Although the authors remain proponents for use of the vaccine in alignment with the CDC vaccination program and recommendations, the previous concerns indicate that new knowledge must be gained and shared. Further research on attenuated vaccines and nonliving or peptide vaccines with equal efficacy should remain the goal, as it is apparent that smallpox vaccine once again will become part of the vaccinologist's and public health official's armamentarium in the decades to come.

Risk of Vaccinia Transfer to the Hands of Vaccinated Persons after Smallpox Immunization

Transmission of vaccinia virus after smallpox vaccination is a concern. We conducted a prospective examination of the protection afforded by vaccination-site bandages in recently vaccinated individuals. After smallpox vaccination, inoculation sites were covered with 2 occlusive dressings. Site assessment and bandage changes occurred every 3-5 days until the site was healed. At each visit, specimens from the vaccination site, outer dressing surface, and contralateral hand were obtained for vaccinia culture. For 148 vaccinated subjects, vaccinia was detected from vaccination lesions of every subject on several occasions. Only 6 (0.65%) of 918 dressing (95% CI, 0.24%-1.4%) and 2 (0.22%) of 926 hand (95% CI, 0.03%-0.78%) specimens tested positive for vaccinia. The mean number of bandage changes was 9.6 (95% CI, 9.17-10.0). Vaccinia autoinoculation did not occur. The rate of vaccinia recovery outside occlusive bandages covering smallpox vaccination sites was remarkably low, suggesting excellent protection against inadvertent transmission.

A genomics-based approach to biodefence preparedness

Since October 2001, the United States has greatly expanded its commitment to biodefence-related research, with $1.75 billion earmarked for this activity in fiscal year 2003.

The goals of this accelerated research and development effort are to understand better the biology of potential bioterror agents and to use this information in the development of new diagnostics, antibiotics and vaccines to protect the world's population against bioterrorism.

Genomics, proteomics and bioinformatics approaches are considered to be key enabling technologies in the development of these new products.

Genome sequence data for all of the principal human pathogens, including most of the potential bioterror agents on the Center for Disease Control and Prevention (CDC) category A–C lists, are available in public databases and provide a new foundation for follow-up studies.

Comparative genomics approaches, together with large-scale methods for studying gene function, such as DNA microarrays, are providing insights into the molecular basis and evolution of pathogenicity, diversity within closely related isolates of the same pathogen and the molecular determinants of host–pathogen interactions.

Genomics-based approaches have already proven to be of great use in the identification of new targets for antimicrobial compounds and in the identification of new vaccine candidates.

Comparative genomics is also providing important information on the natural variability between closely related isolates that is aiding in the development of the new field of microbial forensics.

The anthrax letter attacks in October 2001, followed by the SARS outbreak in early 2003, dramatically illustrated our vulnerability to both deliberate and natural outbreaks of infectious disease. The availability of pathogen genome sequences and high-throughput methods for studying the biology of both pathogens and their hosts have provided new insights into the mechanisms of pathogenesis and host defence. As infectious disease research expands to include major bioterror agents, genomics-based approaches will provide one of the cornerstones of efforts to develop more accurate diagnostics, new therapeutics and vaccines, and further capabilities for microbial forensics.

Emergency medicine tools to manage smallpox (vaccinia) vaccination complications

In December 2002, the federal government began a program to immunize approximately 500000 civilian public health and health care workers with smallpox (vaccinia) vaccine as a part of our pre-event defense against bioterrorism. First responders will likely follow, and the general US population might be offered vaccination in the next 1 to 2 years. Recent reports that suggest the possible association of the vaccine to adverse cardiac events (including deaths), liability concerns for hospitals, and the availability of compensation for workers with vaccine complications have significantly reduced voluntary participation. Vaccinees might experience robust primary takes or serious adverse events, including viral or even bacterial cellulitides, encephalitis, progressive skin destruction, and other life-threatening complications. With the increasing prevalence of immune suppression from both diseases and immunosuppressive medications, complications might be seen in higher frequency than previously reported. Emergency medicine providers and staff must become familiar with clinical presentations and management of vaccine complications. In addition, policies and procedures must be developed to prevent unimmunized providers from inadvertently contacting the active vaccination sites of their patients and, if the providers themselves have active vaccination sites, to protect their patients and their own families.

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).

The Federal Smallpox Vaccination Program: Where Do We Go From Here?

Despite the underwhelming response to the federal government's initiative to inoculate health care workers against smallpox, the Bush administration has indicated that the program will continue and that it could be expanded to include other health care providers, emergency service workers, and others deemed essential for continuity of government. We discuss the reasons for the program's failure to date, outline recent advisories questioning the extent of the vaccination effort, and suggest suspension of further vaccination efforts until certain questions and issues are resolved.