Discussion

This case was the first use of tecovirimat for a laboratory-acquired VACV infection. Tecovirimat was well tolerated by the patient with mild side effects, even with concurrently administered antibiotics. The patient’s clinical course was similar to previously reported VACV needlestick injuries, but the recovery period was longer (earlier cases resolved within 1–2 months) (5–8). The VACV strains used by the patient are not known to have heightened virulence, but whether the clinical course would have worsened without VIGIG or tecovirimat is not known. The independent effect of tecovirimat on the clinical course cannot be determined, and whether its use for similar VACV infections would be warranted is not known.

ACIP recommends vaccination for laboratorians who work with replication-competent VACV, unless vaccination is medically contraindicated (1); however, laboratories working with VACV set their own policies. ACAM2000 is a live-virus vaccine that produces an infectious vaccination site lesion. The vaccine has very low and known risk of complications for the vaccinee and close contacts (1). 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.

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. Even with counseling, laboratorians might have incomplete understanding of the risks and benefits of vaccination. If the vaccine is medically contraindicated, occupational health providers and laboratorians need to carefully weigh whether continued work with replication-competent VACV is prudent. The complexity of managing a vaccination site might dissuade laboratorians from choosing to receive vaccination. However, accidental inoculations often occur in fingers or eyes, causing infections that present special concern for complications, and clinical management can be difficult (8). In addition, laboratory exposures, unlike vaccination, do not have a controlled route of exposure or controlled dose. Previous occupationally acquired VACV infections in unvaccinated workers have required hospitalization, antibiotics for secondary infections, debridement of wounds, and monitoring for functional loss of joints, digits, and vision (5,8). In one case in which recent vaccination did not fully prevent infection, it did reduce the risk for complications, decrease lesion size, and lead to faster recovery (7).

Laboratorians might also underestimate the infection risk from genetically altered, purportedly attenuated VACV strains. Recombinant VACV strains can contain genetic inserts that have unknown or adverse effects on virulence, infectivity, and wound healing (9). Most reports of laboratory-acquired VACV infections were caused by thymidine kinase–deletion strains, which are sometimes mistakenly thought to be avirulent or unlikely to cause human infections (5,8–10).

Researchers working with orthopoxviruses need to have information about the virus strains with which they are working and be provided with procedures to follow in the event of an exposure. Information about the specific strain of the VACV can help health care providers and public health officials determine the risks for complications and develop appropriate treatment plans should an infection occur. Laboratories need to implement biosafety policies and procedures and ensure that all personnel are adequately trained and aware of the risks associated with the work they perform (10). It is important that biosafety information be posted in the laboratory and adequate disinfectant is available. Providing adequate counseling to laboratorians on vaccination and prompt postexposure assessments requires coordination among laboratories, research universities, and medical providers. In the case reported here, the patient did not initiate contact precautions to prevent auto-inoculation or secondary transmission until treated by an occupational health specialist 10 days after the exposure. Clear postexposure procedures can help ensure prompt care by providers knowledgeable about the treatment of VACV exposures, including implementation of infection control practices to prevent secondary transmission.