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Vaccinia - An Overview

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Vaccinia is a vaccine against smallpox and carries cloned antigenic determinants in tests; it can cause mild, cutaneous, and systemic reactions.

Medically reviewed by

Dr. Basuki Nath Bhagat

Published At March 1, 2024
Reviewed AtMarch 20, 2024


The smallpox vaccination is known as the Vaccinia virus. The poxvirus has been examined the most extensively, and investigation into it has shed light on the way viruses interact with host cells and the immune system, as well as how viruses proliferate in general. The complicated morphogenetic process of VACV results in the formation of two distinct infectious virions enclosed in varying numbers of membranes. The initial virion produced, known as the intracellular mature virus (IMV), is surrounded by a single membrane and remains within the cell until cell lysis. When the cell dies, the other virion is released from the body and surrounded by another membrane. If this virion remains on the cell surface, it is known as a cell-associated enveloped virus (CEV), but if it is removed, it is known as an extracellular enveloped virus (EEV).

What Are the Uses of Vaccinia?

Vaccinia virus infections typically cause modest symptoms such as rash and fever but often remain asymptomatic in healthy individuals. The immunological responses triggered by vaccinia virus infection avoid a lethal smallpox infection. The vaccinia virus has been utilized as a live viral vaccination to prevent smallpox. The vaccinia virus vaccine cannot cause smallpox infection because it lacks the smallpox virus, unlike vaccinations that utilize attenuated forms of the virus they protect against. However, sometimes, particular problems or adverse consequences of vaccination become apparent. Immunocompromised persons are far more prone to experiencing this. Recombinant vaccines utilize vaccinia as a carrier to introduce foreign genes into a host to trigger an immune response. More live recombinant vaccines are being created using various poxviruses.

What Are the Various Causes for Vaccinia Infection?

  • Purposeful vaccination is typically the cause of vaccinia infection.

  • Incidents of infection from direct contact with a recently vaccinated person can even be the cause.

  • Risk of unintentional infection of poxviruses among medical professionals and laboratory workers for foreign gene transfer.

What Are the Various Diagnosing Methods?

Laboratory Studies

The diagnosis of vaccinia virus complications is usually simple and requires acquiring a history of recent vaccinia virus exposure by vaccination or contact with a vaccinated individual. Patients with less improvement should get a thorough immune deficiency test.

  • The vague indications and symptoms make diagnosing CNS problems more difficult.

Postvaccinal encephalitis should be addressed in any patient exhibiting neurologic symptoms one to two weeks after being exposed to live vaccinia virus. Vaccinia virus has not been isolated from cerebrospinal fluid (CSF) of encephalitis patients, and CSF examination typically yields normal results, with the exception of elevated pressure; however, CSF study may be recommended to rule out other causes of encephalitis.

Imaging Studies

  • Imaging investigations are not useful in diagnosing vaccinia infection or a postvaccinal consequence, although they can help rule out other sources of disease.

Other Tests

Patients with skin symptoms typically have live virus particles multiplying in their dermal sores analysis to confirm the presence of the vaccinia virus.

  • A biopsy of the skin lesion can be taken and examined under microscopy.

  • Plaque titer test.

  • Western blot.

  • Polymerase chain reaction (PCR).

Histologic Findings

Light microscopy may detect distinctive inclusions (known as Guarnieri bodies) in infected cells' cytoplasm. This differs from the appearance of cells infected with viruses such as herpes simplex virus, which often exhibit intranuclear inclusion bodies.

What Are the Treatments for Complications?

Medical Care: Supportive care is given for problems related to the vaccinia virus.

  • Some people may benefit from VIG, like those who have widespread vaccinia and eczema vaccinatum or who are at a high risk of having problems after getting vaccinia. When used to treat increasing vaccinia and CNS complications, VIG works less well.

  • VIG was made from a mix of plasma from people who had been vaccinated.

  • People who are allergic to VIG or who are sensitive to human pooled blood should not get this medicine.

  • The first medicine used to treat smallpox was Tecovirimat, which is an antibiotic that stops the orthopoxvirus from working. Animal tests using viruses related to the variola virus showed that Tecovirimat was more effective than a placebo at protecting against smallpox. The animals that were treated with tecovirimat had better survival rates compared to those that were given a placebo.

Surgery Care

Surgery usually is unsuccessful in treating problems, but in cases of vaccinia necrosum, debridement of dead tissue might be an option. A biopsy of a suspected lesion can help with the identification.

Which Are the Consultative Services for Vaccinia Infection?

  • Seeking advice from a dermatologist can be beneficial if there is uncertainty in diagnosing a skin problem.

  • Consult an infectious disease and poxvirus virology expert when dealing with suspected cases of vaccinia-related problems.

  • Specialized consultation for particular adverse events is recommended, such as seeing an ophthalmologist for eye issues or a neurologist for nervous system problems.

What Are the Preventive Method for Vaccinia Complications?

  • Regular vaccination with live smallpox (vaccinia) vaccine is advised for individuals in occupations that involve direct contact with cultures or animals contaminated or infected with vaccinia virus that can replicate, including recombinant strains capable of causing infection and producing infectious virus in humans.

  • Health care workers treating patients with vaccinia virus infections and those administering smallpox vaccines who have been exposed to replication-competent vaccinia viruses through contaminated materials can be vaccinated if they follow proper infection prevention protocols.

  • Individuals at high risk, such as those with weakened immune systems or pregnant women, can prevent negative effects from vaccinia by refraining from vaccination.

  • Vaccination for children under 18 should only be administered in cases of smallpox urgency.

Non-emergency use of smallpox vaccine is contraindicated in the following cases:

  • Individuals who have experienced or are currently dealing with atopic dermatitis or other severe exfoliative skin conditions.

  • People with immunosuppressive diseases.

  • Infants under one year old.

  • Pregnant or lactating women.

  • Individuals with a severe allergy to any component of vaccinia vaccine.

  • Individuals with diagnosed heart conditions, regardless of symptoms.

  • Individuals receiving their first dose of the vaccine who have a minimum of three recognized major heart risk factors.


Vaccinia vaccines have been used to treat smallpox for over two centuries. Vaccinia strains have been sequenced, recombinant vectors have been developed using computer technology, and synthetic viral genomes may be manufactured as a result of innovative recombinant DNA methods. The attenuated replication-competent vaccination candidates are being developed to offer a high immunological response while minimizing negative side effects. Genetically modifying poxvirus vectors will not only improve the understanding of these viruses but will also allow everyone to maintain safety while benefiting from the immunogenic properties of replication competence. Despite the vast array of technical and digital possibilities available today, we should take a minute to examine our options for developing optimal future vaccines.

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Dr. Basuki Nath Bhagat
Dr. Basuki Nath Bhagat

Family Physician


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