Vaccinia Virus Reported in Colombian Farm-Workers

According to a recent investigation, there is evidence for the possible emergence of vaccinia virus (VACV) in Columbia, South America.

This is important news since VACV, an orthopoxvirus used in the smallpox vaccine has caused previous human outbreaks in countries, such as Brazil.

This US Centers for Disease Control and Prevention (CDC) early release report published on November 14, 2019, found VACV infections were identified among 31 percent of farmworkers tested in Colombia in 2014. 

And, seropositivity was linked to a history of clinical symptoms in 13 percent of the study participants, suggesting a substantial disease burden.

The CDC said ‘without an identifiable reservoir, control efforts are limited to hygiene and isolation strategies. And, prior smallpox vaccination is not necessarily protective against VACV during outbreaks, likely because of waning immunity.

Another potential concern is the transmission of VACV through the milk of affected cows.

VACV is a member of the genus Orthopoxvirus within the family Poxviridae. Other notable viruses in this lineage include cowpox and monkeypox.

VACV is probably an emerging zoonosis in Colombia and poses a substantial health risk for the populations affected, namely, farm workers involved in the dairy industry. 

In this investigation, the descriptions of VACV-like infections in this population revealed mostly localized, painful, cutaneous lesions affecting the hands, similar to other descriptions of bovine-related VACV infections.

More than half of the patients also reported accompanying systemic symptoms such as fever and malaise, and most of those affected required medical attention and time off work, indicating substantial economic ramifications. 

In addition, two-thirds of the persons who were seropositive and reported a history of symptomatic lesions were ineligible to have received a smallpox vaccine, supporting the idea that unvaccinated persons are at greater risk for symptomatic disease.

More important, nearly one-third of participants who were seropositive would have been ineligible for smallpox vaccination, signifying an ongoing risk for population transmission.

After smallpox was eliminated from the world, routine vaccination against smallpox among the general public was stopped because it was no longer needed, says the CDC.

Smallpox eradication remains one of the most important achievements in science and public health and, during that time, many different VACV strains were used as vaccines around the world. 

Consequently, its escape to the field is a plausible event. 

However, because of concern that variola virus might be used inappropriately, the U.S. government has stockpiled enough smallpox vaccine to vaccinate everyone who would need it, if a smallpox outbreak were to occur.

The CDC says you should get the smallpox vaccine if you are a lab worker who works with a virus that causes smallpox or other viruses that are similar to it.

People who are being vaccinated for the first time have a stronger reaction than those who are being revaccinated.

Smallpox vaccine news

• November 14, 2019 – A Denmark based vaccine company announced the results from the pivotal Phase 3 efficacy trial of its smallpox vaccine, Jynneos™ (MVA-BN®), which has been peer-reviewed and published in The New England Journal of Medicine (NEJM). Importantly, a single dose of MVA-BN induced neutralizing antibody titers comparable with ACAM2000 on Day 14, indicating the potential for use of the vaccine to protect the general population.
• September 3, 2019 – Emergent BioSolutions Inc. announced the U.S. Department of Health and Human Services (HHS) has awarded an agreement valued at approximately $2 billion dollars over 10 years for the continued supply of ACAM2000, a smallpox vaccine.

The city of Medina was the center of the VACV investigation. Medina is located in the department of Cundinamarca, a central region of the Andes Mountains in South America.

Therefore, living in Medina would be expected to be associated with seropositivity. 

However, because our investigation was geographically centered on Medina, very few participants resided outside this municipality. 

A more extensive investigation of other dairy-producing areas in the country might reveal differing results. VACV has been detected in unpasteurized dairy products, but the effect of such contamination on VACV transmission is unknown.

The findings of this investigation are similar to results from studies carried out in Brazil that found a positive correlation between age and seropositivity, although the effect of prior smallpox immunization could not be ruled out.

This outbreak investigation reveals that VACV is likely to become an increasingly important zoonosis in this part of the world, concluded these researchers.

Dr. Rene Styczynski is an infectious disease fellow at Stanford University in Palo Alto, California, USA. Her primary research interests include global infectious disease epidemiology and emerging infections.

These researchers did not disclose any relevant financial relationships.

Vaccinia virus news published by Vax-Before-Travel