An Unusual and Persistent Needlestick Injury

November 26th, 2019

By Gary Evans, Medical Writer

A lab worker who declined protective immunization sustained a needlestick exposure to the Vaccinia virus (VACV) — an orthopoxvirus used in biomedical research — and was subsequently removed from work for four months, the Centers for Disease Control and Prevention reports.

In December 2018, a healthy 26-year-old female laboratorian was injecting VACV into the tail of a mouse when she sustained a needlestick injury to her left index finger. A few months earlier, the lab worker was advised of the risks of working with VACV, but declined immunization with the ACAM2000 vaccine.

Ten days after the needlestick, she presented at occupational health clinic with swelling and a vesicular lesion at the injury site. The treating physician contacted CDC and the San Diego Health Department, which advised monitoring her for evidence of worsening infection.

“On day 12, she was treated at a university-based emergency department for fever, left axillary lymphadenopathy, malaise, pain, and worsening edema of her finger,” the CDC reported. “Health care providers were concerned about progression to compartment syndrome, joint infection, or further spread.”

Complicating the situation, the specific VACV strain could not be determined; thus, the severity and progress of the infection could not be predicted. The patient received a single 6,000 IU/kg dose of Vaccinia Immune Globulin Intravenous (VIGIV) and started a 14-day course of twice-daily oral tecovirimat.

“She also received clindamycin and cephalexin because of concern about possible secondary bacterial infection,” the CDC reported. “Within 48 hours of treatment initiation, the fever and lymphadenopathy resolved, and the local pain and edema decreased.” The occupational health office furloughed the patient from lab work for approximately four months, citing the local necrosis of the wound site and the risk for VACV transmission. Again, no secondary transmission or auto-inoculation occurred.

Upon further investigation, it was determined that a genetically altered strain of VACV could have been involved in the needlestick.

“Although the patient had declined vaccination when it was initially offered, during this investigation she reported that she did not appreciate the extent of infection that could occur with VACV when vaccination was first offered,” the CDC concluded. “She also cited the challenges of managing the infectious lesion at the vaccination site and potential vaccination adverse events as factors contributing to her initial decision to decline vaccination.”

The CDC recommends vaccination for laboratorians who work with replication-competent VACV unless vaccination is medically contraindicated. Counseling before working with VACV needs to include benefits of vaccination, risks of working with VACV in the laboratory, vaccination-associated adverse events, care of the vaccination site, and contraindications to vaccination.

“However, laboratories working with VACV set their own policies,” the CDC concluded. “ACAM2000 is a live-virus vaccine that produces an infectious vaccination site lesion. Appropriate vaccination site care requires careful monitoring of the site and adherence to infection control precautions until the crust separates and a new layer of skin forms.”

While laboratorians may wish to avoid the vaccine in lieu of these site management requirements, accidental inoculations may be a worse alternative. “[These] often occur in fingers or eyes, causing infections that present special concern for complications, and clinical management can be difficult,” the CDC warned. “In addition, laboratory exposures, unlike vaccination, do not have a controlled route of exposure or controlled dose."

For more on this story see the January 2020 issue of Hospital Employee Health.