Inadvertent self-injection: The risk associated with oil-based vaccines
Worker safety is of utmost importance in any agricultural setting, particularly when handling veterinary vaccines or products. These substances play a crucial role in ensuring the health and well-being of livestock, but they can also pose potential risks to farm workers if not handled properly. Veterinarians have the duty to inform the client of the nature of the medications they prescribed, including any danger associated with them, and their safe disposal.1 This responsibility extends also once it is in the hands of the end user, i.e.: the farm workers and producers. This “News and Views” aims to highlight the risk associated with the use of some veterinary products and outlines some differences in composition of vaccines that should be taken into consideration when choosing a protocol.
Needlestick injuries to end users are an inherent risk of any medical intervention that requires handling needles. Significant efforts and attention have been placed to reduce needlestick injuries in human medicine. The main driver in changing attitudes in human medicine was bloodborne viral pathogens such as hepatitis B virus, hepatitis C virus, and human immunodeficiency virus (HIV), just to name a few.2
Accidental self-injection injury is a common occurrence among veterinary and farm workers. In these populations, according to Rubin et al., the lifetime occurrence of accidental injection during vaccination of animals ranges from 64 to 93%.3 In some countries, rates of between 9 and 75 injuries per 100 person-years of practice have been reported.4 This is likely true when handling automatic syringe injectors used in mass vaccinations of animals, like those used in swine production. Furthermore, the incidence is probably much higher since these injuries are usually not reported. In a previous survey conducted by the American Association of Swine Practitioners (AASV), amongst the 586 respondents reporting a needlestick injury, vaccines were the most common exposures (40% ±2).5 Fortunately, most of these injuries are asymptomatic or cause only mild, self-limited symptoms, but a portion of these injuries can have serious consequences. If the vaccine contains an oily adjuvant, there is an increased likelihood of untoward consequences.2,6,7
Self-injection of an oil-based animal vaccine can trigger a painful foreign body reaction and potentially lead to a prolonged chronic granulomatous reaction, sometimes complicated with sterile abscess formation at the injection site.6 A granuloma is a localized area of inflammation characterized by the accumulation of immune cells and the formation of nodules. Granulomas can develop as a response to foreign substances, including vaccine components, and are the body's attempt to isolate and contain the injected material. Self-injection commonly occurs in the hand. In a retrospective study conducted in 2022, all patients had injury to the non-dominant hand mostly involving the thumb or another finger. The mean hospitalization time was 3.75 days (1–10). One third of the patients needed to undergo major surgical debridement and drainage during hospitalization.3
Anatomically the hands lack buffer zones, such as fat, and represent a complex structure with plenty of terminal arteries, nerves, and tendons. These contribute to the severity and extent of complication when compared with other parts of the human body. Oil-based products tend to disperse when injected in the tendon sheet, extending the consequence to a wider area. As an example, a farm worker’s inadvertent self-injection of an oil-based bovine vaccine into his finger resulted in amputation of the finger because of ischemic necrosis, following increased pressure in the flexor tendon sheath.8 Furthermore, the potential risk of infection or adverse effects from other vaccine constituent, especially in farm conditions, should not be forgotten.4 According to Windsor et al., several injured patients, when asked about the adequacy of the advisory material on the package or in the accompanying information sheet, admitted that they had not read it, but would now suggest that clearer warnings could be of assistance in ensuring early medical assessment and surgical intervention where appropriate.7 This explains why oil-emulsion vaccines usually have the following mention on their label: “Use extreme caution when injecting to avoid self-injection since it can cause serious local reaction”. Therefore, all self-injection with an oil-based vaccine should be treated seriously and urgently.
Farm workers usually receive training on handling, storing, and application of veterinary vaccines and products, but the potential hazards associated with these substances are often overlooked. Prioritizing worker safety not only protects the well-being of individuals, but also contributes to the overall success and sustainability of the farm operation. Effective communication between farm management, workers, and veterinarians is crucial for ensuring the worker’s safety.
Nowadays, with the rapid turnover in farm employees, sometimes of foreign origin, it should be taken into consideration that new, inexperienced workers may not always have the baseline knowledge of needlestick injuries and of the risk associated with certain products. It is well known that proper storage and handling of veterinary vaccines and products are essential to maintain their effectiveness but work still needs to be done on preventing accidental exposures. According to the UK Health and Safety Executive (HSE) regarding administration of veterinary medicines to livestock, effective control measures are needed to reduce the risks to human health. They highly recommend prioritizing a less hazardous veterinary product, i.e.: a water-based vaccine instead of an oil-based one.9
It is prudent for veterinarians and veterinary practices, when dispensing or prescribing injectable treatments, to proactively address issues such biohazardous risk associated with needlestick injuries, particularly regarding oil-based vaccines. None of the Boehringer Ingelheim swine vaccines in the FLEX and Enterisol™ families contain oily adjuvants, which makes them safer not only for the pigs, but also for the people who take care of them.
References:
1. Quebec Code of ethics of veterinary surgeons, Division II: “Duties towards the clients”, Section 2.: “Integrity”, Item 9, (M-8, r. 4 / 3 of 13), Quebec Official Publisher, Updated to December 1, 2022
2. Weese JS, et al. Needlestick injuries in veterinary medicine. Can Vet J. 2008; 49:780–784
3. Rubin G, et al. Hand function following accidental automatic animal syringe injector injuries. Nature Scientific Reports. 2022; 12:21061
4. Burke F, et al. Needlestick and inoculation injuries in veterinary and animal workers. In Practice. 2017; 39: 138-41.
5. Hafer A, et al. Occupational hazards reported by swine veterinarians in the United States. J. Swine Health Prod. 1996; 4: 128–141
6. Jones D. Accidental self-inoculation with oil-based veterinary vaccines. N Z Med J. 1996; 109:363–365
7. Windsor PA, et al. Injury caused by self-inoculation with a vaccine of a Freund’s complete adjuvant nature (Gudair ™) used for control of ovine paratuberculosis. Australian Veterinary Journal. 2005; Volume 83, No 4: 216-220
8. O’Neill J, et al. The effects of injection of bovine vaccine into a human digit: A case report. Environmental health A global access science source. 2005; 4:21.
9. UK Health and Safety Executive Website, guidance recommendation, Veterinary medicines: Safe use by farmers and other animal handlers, 2012 (assessed May 2023)