By Philip R. Fischer, MD, DTM&H
Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN; Department of Pediatrics, Sheikh Shakhbout Medical City, Abu Dhabi, United Arab Emirates
SYNOPSIS: In a large Canadian study, lack of COVID vaccination was associated with an increased incidence of being injured in a car crash.
SOURCE: Redelmeier DA, Wang J, Thiruchelvam D. COVID vaccine hesitancy and risk of a traffic crash. Am J Med 2023;136:153-162.
The authors believed that hesitancy to receive COVID vaccination is a marker of a psychological make-up that might relate to road traffic safety behaviors. Thus, they sought to determine if there is an association between COVID vaccination and risk of being involved in a car crash.
Redelmeier and colleagues determined COVID vaccination status of adults (> 18 years of age) from a centralized government vaccine database and post-car crash injury data from hospital records in the province of Ontario, Canada, during a one-month study period in 2021. Vaccines were readily available, and the investigators assumed that vaccine hesitancy was the only significant reason not to be vaccinated. Age, sex, living situation (urban vs. rural), and socioeconomic status were identified using demographic databases. Healthcare record databases were reviewed to note significant medical diagnoses, including alcohol misuse, sleep apnea, depression, and dementia. Car crash data identified the status of the individual (driver, passenger, pedestrian), time of day of the crash, and triage severity score.
The study included 11,270,763 adults. Overall, 84% had been vaccinated for COVID at the beginning of the study month. The unvaccinated group was statistically younger, more likely to live in a rural setting, and more often ranked in the lower socioeconomic strata. The unvaccinated were more likely to have had alcohol misuse and depression diagnosed but less likely to carry diagnoses of sleep apnea, diabetes, cancer, and dementia.
Within this population, 6,682 individuals received emergency medical care for a car crash during the study month; 25% of those had not received COVID vaccination. The relative risk for a car crash injury was 1.72 (P < 0.001) in the unvaccinated group. This statistically significant increased risk held true for those younger than 65 years of age, for both sexes, for those in both urban and rural settings, and for those of differing socioeconomic statuses. Vaccine status was not related to an increased risk of a car crash only for those older than age 65 years, those who misused alcohol, and those with diabetes. Severity of injury was not related to vaccine status.
The authors pointed to other studies showing an increased risk of car crashes in taxi drivers with personality disorders, young drivers with “an aggressive personality pattern,” and motorcycle drivers with particular personal temperaments. Although they stated that their study did not prove causality between vaccine acceptance and car crashes, the authors suggested that a distrust of government or a belief in personal freedoms could be at the base of both COVID non-vaccination and risky driving behaviors. However, the association between non-vaccination and motor vehicle injury cannot merely be related to driving habits, since the link between non-vaccination and injury also held true for pedestrians.
The authors pointed to the need for better safety education, especially in unvaccinated adults. They also suggested the possibility of altering insurance policies for the unvaccinated.
COMMENTARY
Redelmeier and colleagues have demonstrated provocative findings, specifically that being unvaccinated for COVID is associated with an increased risk of requiring medical care for injuries sustained in car crashes. While accepting the rigor of the study, scientific readers will be careful to infer neither causality between vaccine status and risk of car crashes nor that vaccination would prevent the same individuals from being involved in crashes.
The association between non-vaccination and car crashes was clear in this study, but other confounding factors also were identified. Nonetheless, the association between non-vaccination and crashes held up for most age groups, both sexes, urban and rural dwellers, and people with a variety of health conditions.
The authors seemed to assume that lack of COVID vaccination was due to “vaccine hesitancy.” In a setting where only 16% of adults were not vaccinated, their assumption might be correct. However, it is possible that some of the unvaccinated were neither resistant to nor hesitant toward COVID vaccination; there could have been contraindications to vaccination or personal challenges accessing vaccination. Those with poor access to vaccination (apparently rare in Canada at the time of the study) and those with medical contraindications to vaccination (perhaps more likely in those older than 65 years of age when there was not an increased risk of crashes related to non-vaccination) might not have had the presumed “psychology” that increases the risk of crashes and crash injuries. Nonetheless, the statistical association between non-vaccination and crash-related injury still was significant.
Good evidence supports both COVID vaccination and safe driving behaviors. Whether there is a single personality type or psychological status underlying both COVID non-vaccination and unsafe behaviors on roads, physicians still can advocate for both vaccination and safe driving. In addition, the notion that insurance policies should cost more for individuals who, by refusing vaccinations, are clearly identified as being at increased risk of needing expensive care both for COVID and for road-related trauma may resonate with many readers.
