Young man doctor nurse in medical protective face mask talking to patients sitting and waiting in line before vaccination against covid-19 virus during pandemic in medical clinic office

Bioethics Forum Essay

Should Covid Vaccination Schedules Deviate from the Status Quo–as a Last Resort?

Last month, with concerns over the supply and coordinated administration of coronavirus vaccines escalating, the Centers for Disease Control and Prevention conceded that “any available mRNA COVID-19 vaccine” may be used to complete vaccination in “exceptional situations” preventing multidose manufacturer matching. While presented solely as a last resort, this guidance reflects a dilemma currently sweeping across the medical and health policy worlds: given limited supply, should vaccination efforts—still only authorized for emergency use in this country—deviate from evidence-driven, studied regimens to maximize individuals reached?

We think not. We favor sticking with tested methods that have been subjected to intense independent scrutiny, and continuing population-level research, before permitting risky deviations.

Generally speaking, the goal of vaccination is to minimize disease transmission, morbidity and mortality. Covid-19 immunization is no different. What is different now, however, is that scientists, health care workers, policy makers, and everyone in between is working with limited data as they attempt to craft a maximally effective, yet rapid rollout.

Various proposals aimed at getting vaccines “into as many arms as possible” have emerged—and, in some cases, taken hold—over the past few weeks, as worries about botched rollouts and new strains increasingly permeate global medical and political sensibilities. The United Kingdom, for instance, has prioritized administration of first doses over completion of standard two-dose courses for its citizens, extending inter-dose times from three to twelve weeks. Other proposals include halving, or altogether cancelling, second doses, and even purposefully mixing doses from different vaccine manufacturers.

Proponents of such alternative approaches, which deviate from vaccine protocols interrogated and independently validated in major trials, contend that the gravity of Covid’s countless tolls—social, medical, economic, emotional—warrants experimentation with measures of even “decent efficacy” in a drastic drive to “save most lives fastest.” Deviation from studied vaccination schedules, however, only makes sense if reasonably expected to safely save more lives in less time.

Unfortunately, evidence supporting the efficacy of alternative vaccination approaches is currently minimal and challenging to interpret. The UK’s Joint Commission on Vaccination and Immunization argues, for instance, that “high levels of protection are obtained” after first vaccine doses; one-dose efficacy rates, however, range from roughly 50% to 90% depending on the reporting source—and, unsurprisingly, vary according to days from vaccination, vaccine manufacturer, incidence of mutation exposure, criteria for Covid-positive designation, and population age, not all of which are consistently documented.  Pfizer’s trials, which the company says were “not designed to assess the efficacy of a single-dose regimen,” suggest a one-dose efficacy of 52%; this value, however, reflects only symptomatic disease in individuals who fell away from the trial before a second dose without longitudinal follow-up for later infection (versus continued immunity). Furthermore, it does not appear to take into account some delay in immune response, counting Covid cases occurring even immediately post-vaccination.Public Health England cut this data differently, reporting almost 90% efficacy of first Pfizer doses 15-to-21 days after immunization.In separate trials, Israel’s Clalit Research Institute identified a “decrease of about 33%” in positive test rates 14 days after first vaccination.”

All of these metrics differ not only in magnitude and reflected population, but, perhaps even more importantly, in the language used to describe them—percent efficacy, percent decrease, percent protection. With such variable and vague language, these numbers—not intended as rigorously-tested facts in the first place—are challenging to summarize for significance in application and strategy decision-making.

Notably, trials focused on evaluating the efficacy of single vaccine doses, multiple doses from different manufacturers, or other alternative regimens have not been—and, arguably, cannot ethically be—conducted, given existing data demonstrating that two matched doses work, and work well. Evidence to support other regimens thus remains collected observationally, in varied populations lacking long-term follow-up.

At least in the United States, expert opinion largely favors staying with what’s known—holding fast to solid data when much else is uncertain. FDA officials even warn about serious “potential for harm,” stressing how changes in vaccination practice “not supported by adequate scientific evidence may ultimately be counterproductive to public health.” Individuals falsely assuming immunity might unwittingly transmit the virus. “Off-script” vaccine usage may encourage even less substantiated regimens—partial dosing, or mixing vaccines across mechanisms of action. Public trust in vaccination, even as a general practice, may degrade as guidelines shift without clear rationale and less certain outcomes. Liability for harms caused remains unclear. Most importantly, though, acting without dependable data, we risk forfeiting our shared global goal—to save the most lives fastest.

We just don’t know if other options—new “creative” ideas—will work better than what we are doing now. So, let’s focus on increasing production and improving distribution, maintaining prudent behaviors and, for the time being, stick to the script.

Nina Shevzov-Zebrun is a third-year medical student at NYU Grossman School of Medicine. Arthur Caplan, PhD, is the Drs. William F. and Virginia Connolly Mitty Professor of Bioethics and the founding director of the Division of Medical Ethics at NYU Grossman School of Medicine. He is a Hastings Center fellow and member of the Hastings Center’s advisory council, @ArthurCaplan. Brendan Parent is an assistant professor of bioethics and director of Transplant Ethics and Policy Research at NYU Grossman School of Medicine, @parent_brendan.

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