COVID Nonvaccination Linked With Avoidable Hospitalizations

Kate Johnson

June 01, 2023

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Lack of vaccination against COVID-19 was associated with a significantly higher risk for hospitalization, compared with vaccinated status and boosted status, new evidence suggests.

A retrospective, population-based cohort study in Alberta, Canada, found that between late September 2021 and late January 2022, eligible unvaccinated patients with COVID-19 had a nearly 10-fold higher risk for hospitalization than did patients who were fully vaccinated with two doses. Unvaccinated patients had a nearly 21-fold higher risk than did patients who were boosted with three doses.

"We have shown that eligible nonvaccinated persons, especially in the age strata 50-79 years, accounted for 3000-4000 potentially avoidable hospitalizations, 35,000-40,000 avoidable bed-days, and $100–$110 million [Canadian dollars] in avoidable healthcare costs during a 120-day period coinciding with the fourth (Delta) and fifth (Omicron) COVID-19 waves, respectively," write Sean M. Bagshaw, MD, chair of critical care medicine at the University of Alberta, Edmonton, Canada, and colleagues.

The findings were published May 10 in the Canadian Journal of Public Health.

"Unsatisfactory" Vaccine Uptake

While a previous study by Bagshaw et al. recently showed that higher vaccine uptake could have avoided significant intensive care unit admissions and costs, the researchers sought to expand their analysis to include non-ICU use.

The current study examined data from the government of Alberta and the Discharge Abstract Database to assess vaccination status and hospitalization with confirmed SARS-CoV-2. Secondary outcomes included avoidable hospitalizations, avoidable hospital bed-days, and the potential cost avoidance related to COVID-19. 

During the study period, "societal factors contributed to an unsatisfactory voluntary vaccine uptake, particularly in the province of Alberta," write the authors, adding that "only 63.7% and 2.7% of the eligible population in Alberta [had] received two (full) and three (boosted) COVID-19 vaccine doses as of September 27, 2021." 

The analysis found the highest number of hospitalizations among unvaccinated patients (n = 3835), compared with vaccinated (n = 1907) and boosted patients (n = 481). This finding yielded a risk ratio (RR) of hospitalization of 9.7 for unvaccinated patients, compared with fully vaccinated patients, and an RR of 20.6, compared with patients who were boosted. Unvaccinated patients aged 60-69 years had the highest RR for hospitalization, compared with vaccinated (RR, 16.4) and boosted patients (RR, 151.9).

The estimated number of avoidable hospitalizations for unvaccinated patients was 3439 (total of 36,331 bed-days), compared with vaccinated patients, and 3764 (total of 40,185 bed-days), compared with boosted patients. 

The avoidable hospitalization-related costs for unvaccinated patients totaled $101.4 million (Canadian dollars) if they had been vaccinated and $110.24 million if they had been boosted.

"Moreover, strained hospital systems and the widespread adoption of crisis standards of care in response to surges in COVID-19 hospitalizations have contributed to unnecessary excess deaths," write the authors. "These are preventable and missed public health opportunities that provoked massive health system disruptions and resource diversions, including deferral of routine health services (e.g., cancer and chronic disease screening and monitoring and scheduled vaccinations), postponement of scheduled procedures and surgeries, and redeployment of healthcare professionals." 

Bagshaw told Medscape Medical News that he was not surprised by the findings. "However, I wonder whether the public and those who direct policy and make decisions about the health system would be interested in better understanding the scope and sheer disruption the health system suffered due to COVID-19," he said.

The current study suggests that "at least some of this could have been avoided," said Bagshaw. "I hope we — that is the public, users of the health system, decision-makers and healthcare professionals — can learn from our experiences." Studies like the current analysis "will reinforce the importance of timely and clearly articulated public health promotion, education, and policy," he added.

Economic Benefit Underestimated  

Commenting on the study for Medscape, David Fisman, MD, MPH, an epidemiologist and professor at the University of Toronto's Dalla Lana School of Public Health, said, "The approach these investigators have taken is clear and straightforward. It is easy to reproduce. It is also entirely consistent with what other scientific groups have been demonstrating for a couple of years now." Fisman was not involved with the study.

A group led by Fisman as senior author has just completed a study examining the effectiveness of the Canadian pandemic response, compared with responses in four peer countries. In the as-yet unpublished paper, the researchers conclude that "relative to the United States, United Kingdom, and France, the Canadian pandemic response was estimated to have averted 94,492, 64,306, and 13,641 deaths, respectively, with more than 480,000 hospitalizations averted and 1 million QALY [quality-adjusted life-years] saved, relative to the United States. A United States pandemic response applied to Canada would have resulted in more than $40 billion in economic losses due to healthcare expenditures and lost QALY; losses relative to the United Kingdom and France would have been $21 billion and $5 billion, respectively. By contrast, an Australian pandemic response would have averted over 28,000 additional deaths and averted nearly $9 billion in costs in Canada."

Fisman added that while the current researchers focused their study on the direct protective effects of vaccines, "we know that, even with initial waves of Omicron, vaccinated individuals continued to be protected against infection as well as disease, and even if they were infected, we know from household contact studies that they were less infectious to others. That means that even though the implicit estimate of cost savings that could have been achieved through better coverage are pretty high in this paper, the economic benefit of vaccination is underestimated in this analysis, because we can't quantify the infections that never happened because of vaccination."

The study was supported by the Strategic Clinical Networks, Alberta Health Services. Bagshaw declared no relevant financial relationships. Fisman has taken part in advisory boards for Seqirus, Pfizer, AstraZeneca, Sanofi, and Merck vaccines during the past 3 years.

Can J Public Health. Published May 10, 2023. Full text

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.

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