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Vaccine Detail

Vaccine Information
  • Vaccine Name: Dryvax
  • Target Pathogen: Variola virus
  • Target Disease: Smallpox
  • Product Name: Smallpox Vaccine, Dried, Calf Lymph Type
  • Tradename: Dryvax
  • Manufacturer: Wyeth Pharmaceuticals Inc
  • Vaccine Ontology ID: VO_0000035
  • CDC CVX code: 75
  • Type: live vaccinia virus vaccine
  • Status: Licensed
  • Location Licensed: USA (License #0003)
  • Host Species for Licensed Use: Human
  • Preparation: This vaccine is derived from NYCBH strain. It is lyophilized calf lymph and comes with a diluent containing 50% glycerol and 0.25% phenol in sterile water for injection, USP (Parrino et al., 2006).
  • Immunization Route: percutaneous (scarification)
  • Virulence: Dryvax was used to vaccinate military personnel and a select civilian population beginning in 2002. In these highly screened individuals, there were fewer adverse events than anticipated on the basis of the historical data, and no cases of progressive vaccinia or eczema vaccinatum. However, a new finding of cardiac complications have become a cause for concern. Although European and Australian literature from the 1950s, 1960s, and 1970s reported fatal and nonfatal postvaccinial cardiac complications, such reports were rare in the United States. At the time, this difference was believed to have been related to the less reactogenic strain of vaccinia virus used in the United States. However, the findings from the military and civilian vaccination programs indicate those with cardiac disease should not receive vaccinia in nonemergent settings. Of the 38,885 civilian smallpox vaccines administered between 2002 and 2003, there were 21 cases of myopericarditis and 10 ischemic cardiac events, of which 2 were fatal. In the military program as of June 2006, there were more than 1 million vaccinations and 120 cases of myopericarditis. The 16 cases of ischemic heart disease were consistent with rates in unvaccinated military recruits of the same age. The investigation of 8 fatalities after vaccination determined 1 death from an acute lupuslike illness may have a causal relationship to vaccine. In addition, vaccination was thought possibly to contribute to the sudden death of a 26-year-old military recruit 16 days after he received smallpox and influenza vaccinations. However, autopsy revealed myocarditis with parvovirus B in the cardiac muscle and no evidence of vaccinia virus (Parrino et al., 2006).
  • Storage: 2° to 8°C (36° to 46°F) (FDA: Dryvax).
  • Approved Age for Licensed Use: 18 and older
  • Contraindication: The vaccine should not be administered to anyone with known hypersensitivity to any component of the vaccine, individuals who have eczema and women who may be or want to become pregnant (FDA: Dryvax).
  • Description: Dryvax is the only US Food and Drug Administration (FDA)–licensed vaccine in the United States. Vaccination of the general public stopped in the US in 1972, and production of this vaccine stopped in 1982. Recent studies were performed evaluating clinical and immunologic responses to diluted vaccine in volunteers who had not previously been immunized to determine whether this stock vaccine could safely be diluted to provide more available doses. At dilutions of 1:5 or 1:10 (107 plaque-forming units [pfu]), the vaccine retained its potency and was able to elicit adequate immune responses (Parrino et al., 2006).
Host Response

Human Response

  • Host Strain: federal, state, and local potential first responders
  • Vaccination Protocol: A total of 37,901 volunteers in 55 jurisdictions received at least 1 dose of smallpox vaccine (Casey et al., 2005).
  • Persistence: Although the vaccine is effective, it is unclear how long it provides protection. Data suggest vaccine-specific memory B cells may persist for more than 50 years after vaccination, but not knowing which immunologic responses determine protection makes it difficult to define the duration of protective immunity.17 Alternative vaccine strategies designed to be safer than the presently available live virus vaccines are being pursued (Parrino et al., 2006).
  • Side Effects: A total of 590 adverse events (72%) were reported within 14 days of vaccination. Nonserious adverse events (n = 722) included multiple signs and symptoms of mild and self-limited local reactions. One hundred adverse events (12%) were designated as serious, resulting in 85 hospitalizations, 2 permanent disabilities, 10 life-threatening illnesses, and 3 deaths. Among the serious adverse events, 21 cases were classified as myocarditis and/or pericarditis and 10 as ischemic cardiac events that were not anticipated based on historical data. Two cases of generalized vaccinia and 1 case of post-vaccinial encephalitis were detected. No preventable life-threatening adverse reactions, contact transmissions, or adverse reactions that required treatment with vaccinia immune globulin were identified. Serious adverse events were more common among older revaccinees than younger first-time vaccinees (Casey et al., 2005).
  • Efficacy: A total of 38,885 smallpox vaccinations were administered, with a take rate of 92%. VAERS received 822 reports of adverse events following smallpox vaccination (overall reporting rate, 217 per 10,000 vaccinees) (Casey et al., 2005).
  • Description: The US Department of Health and Human Services (DHHS) implemented a preparedness program in which smallpox vaccine was administered to federal, state, and local volunteers who might be first responders during a bioterrorism event (Casey et al., 2005).

Human Response

  • Host Strain: US service members and DoD civilian workers eligible for smallpox vaccination
  • Vaccination Protocol: To develop vaccination policy, the US Department of Defense (DoD) drew from its own physicians, scientists, and administrators as well as colleagues in government and academia. The military vaccination program included vaccination for smallpox epidemic response teams (2000-5000 people) to assist with epidemic control and contact tracing in an outbreak, medical teams for hospitals and clinics (10,000-25,000 people) to care for smallpox cases, and operational forces (up to 500,000 people) to preserve critical capabilities. The licensed full-strength smallpox vaccine containing the NYCBH strain of vaccinia was used. First-time vaccination entailed punctures with a bifurcated needle. Previous vaccinees received 15 punctures. Those who did not respond with a major reaction as defined by the World Health Organization (WHO) were vaccinated again. Smallpox vaccinations began at 4 pilot sites: Walter Reed Army Medical Center, Washington, DC; Aberdeen Proving Ground, MD; Wilford Hall Air Force Medical Center, Lackland Air Force Base, San Antonio, TX; and the National Naval Medical Center, Bethesda, MD. For quality control, clinics tracked the vaccination response rates of the first 25 people for each vaccinator (Grabenstein et al., 2003).
  • Persistence: In addition to unacceptable side effects and problems related to production, although the vaccine is effective, it is unclear how long it provides protection. Data suggest vaccine-specific memory B cells may persist for more than 50 years after vaccination, but not knowing which immunologic responses determine protection makes it difficult to define the duration of protective immunity.17 Alternative vaccine strategies designed to be safer than the presently available live virus vaccines are being pursued (Parrino et al., 2006).
  • Side Effects: One case of encephalitis and 37 cases of acute myopericarditis developed after vaccination; all cases recovered. Among 19,461 worker-months of clinical contact, there were no cases of transmission of vaccinia from worker to patient, no cases of eczema vaccinatum or progressive vaccinia, and no attributed deaths (Grabenstein et al., 2003).
  • Efficacy: In 5.5 months, the DoD administered 450,293 smallpox vaccinations (70.5% primary vaccinees and 29.5% revaccinees). In 2 settings, 0.5% and 3.0% of vaccine recipients needed short-term sick leave. Most adverse events occurred at rates below historical rates (Grabenstein et al., 2003).
  • Description: The US implemented a program of smallpox vaccinations for approximately 500,000 military personnel. The directive came as part of a national program of preparedness against biological attack. Pre-attack vaccination was determined to be the best way to personally protect troops so that they could continue their missions. The program was therefore mandatory for designated service members and employees except those with contraindications (Grabenstein et al., 2003).
Casey et al., 2005: Casey CG, Iskander JK, Roper MH, Mast EE, Wen XJ, Torok TJ, Chapman LE, Swerdlow DL, Morgan J, Heffelfinger JD, Vitek C, Reef SE, Hasbrouck LM, Damon I, Neff L, Vellozzi C, McCauley M, Strikas RA, Mootrey G. Adverse events associated with smallpox vaccination in the United States, January-October 2003. JAMA : the journal of the American Medical Association. 2005 Dec 7; 294(21); 2734-43. [PubMed: 16333009 ].
FDA: Dryvax: FDA: Dryvax Vaccine for Variola Virus []
Grabenstein et al., 2003: Grabenstein JD, Winkenwerder W Jr. US military smallpox vaccination program experience. JAMA : the journal of the American Medical Association. 2003 Jun 25; 289(24); 3278-82. [PubMed: 12824209 ].
Parrino et al., 2006: Parrino J, Graham BS. Smallpox vaccines: Past, present, and future. The Journal of allergy and clinical immunology. 2006 Dec; 118(6); 1320-6. [PubMed: 17157663 ].