By Stan Deresinski, MD, FACP

Clinical Professor of Medicine, Stanford University

SYNOPSIS: Vaccine (non-COVID-19) contamination as a result of improper handling led to injection site infections due to Mycobacterium porcinum, a rapid growing non-tuberculous mycobacterium present in the environment.

SOURCES: Blau EF, Flinchum A, Gaub KL, et al. Mycobacterium porcinum skin and soft tissue infections after vaccinations — Indiana, Kentucky, and Ohio, September 2018–February 2019. MMWR Morb Mortal Wkly Rep 2021;70:1472-1477.

Erratum: Vol. 70, No. 42. MMWR Morb Mortal Wkly Rep 2021;70:1560.

The Kentucky Department for Public Health (KDPH) received notification on Dec. 4, 2018, from a local health department that it had evaluated three patients with skin abscesses at the site of receipt of vaccination at their workplace and provided by “company A.” The vaccines administered included influenza; hepatitis A; pneumococcal; or tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap). On learning that company A had received similar reports but had not, in turn, reported them to the Vaccine Adverse Event Reporting System (VAERS) or the local health department, the company was ordered to cease vaccine administration and to sequester remaining vaccines and supplies. Two days later, notifications were sent to five counties in which the company had been performing vaccinations. KDPH also notified seven businesses initially identified by company A as sites where they were vaccinating, but KDPH subsequently identified an additional 17 sites that company A had failed to report to them. Eventually, the investigation involved a total of 24 businesses in Kentucky, Indiana, and Ohio that had contracted with company A to vaccinate their employees and 101 employees meeting the case definition of a vaccine site reaction within 150 days.

The median time to onset of these events after vaccination was 14 days (range 0-126 days). The most frequently reported findings were nodules, erythema, and pain, each occurring in > 84% of cases, with drainage in 57.4%. Thirty clinical specimens sent to public health laboratories yielded Mycobacterium porcinum on culture. Pulsed field gel electrophoresis performed at the Centers for Disease Control and Prevention (CDC) indicated these comprised two closely related clusters, with only a single band difference.


M. porcinum is a “rapid grower” of the Mycobacterium fortuitum group. Like other organisms of this group, it is present in the environment. Although rarely identified as a cause of human infection, it previously was reported to cause an outbreak of infection in 24 inpatients over five years as a consequence of contamination of the water supply of a Galveston, TX, hospital.1 A 2004 report indicates that clinical isolates were susceptible to ciprofloxacin, sulfamethoxazole, and linezolid, and susceptible or intermediate to cefoxitin, clarithromycin, imipenem, and amikacin.2

In the vaccine-related outbreak of skin and soft tissue infections reported by the CDC, the epidemiological, microbiological, and molecular findings indicated single source contamination, which most likely occurred during syringe preparation. The investigation identified multiple problems, including improper vaccine storage, handling, and administration, together with lack of training and professional oversight of the involved non-medical personnel. This outbreak was completely preventable, but the breadth and depth of the breakdown in the process described in this report is astounding.


  1. Brown-Elliott BA, Wallace RJ Jr, Tichindelean C, et al. Five-year outbreak of community- and hospital-acquired Mycobacterium porcinum infections related to public water supplies. J Clin Microbiol 2011;49:4231-4238.
  2. Wallace RJ Jr, Brown-Elliott BA, Wilson RW, et al. Clinical and laboratory features of Mycobacterium porcinum. J Clin Microbiol 2004;42:5689-5697.