The hunt is on for a vaccine for Covid-19, which has killed more than 600,000 people.
The current frontrunners include an mRNA vaccine from Moderna; a candidate vaccine from AstraZeneca and Oxford University; a Chinese vaccine from the military and biotech company CanSigo Biologics; and an mRNA-based vaccine from German company BioNTech and Pfizer.
While a candidate could be approved this year, it remains to be seen whether the vaccine will confer temporary or long-term immunity, or how many doses will be required, as doubling the number of jabs could complicate worldwide immunization efforts.
But bioethicists and public health experts all agree that manufacturing doses for 8 billion people quickly is an insurmountable challenge.
So someone will have to decide who should get the vaccine first — and why.
In the United States, committees have begun to form to discuss this tricky issue. An advisory committee of external health experts is advising the Centers for Centers for Disease Control and Prevention on an equitable framework. The National Academies of Medicine announced earlier this month that its committee will "develop an overarching framework to assist policymakers in the U.S. and global health communities."
Some of the most challenging questions they face include whether pregnant women (normally the last to get a vaccine) should be higher up on the list, or whether Black and Latino people — who have been disproportionately affected by the virus — should get access to the vaccine before the rest of the population.
Then there are the global considerations. Task forces have formed to come up with a "fair and equitable" framework to distribute the vaccine between countries, but face numerous practical challenges.
Arthur Caplan, professor of bioethics at New York University Langone Medical Center, thinks some countries will have vaccines to spare, while others won't have access to many at all. Some nations could use their leverage over vaccines as a way to curry favor or to negotiate trade deals. Enforcing safety and efficacy is another sticking point because not every country has the same quality-control processes.
"Internationally, there's a lot of talk about how every life is valuable," he said. "But that doesn't address what you do in practical terms if there's a shortage."
Caplan is also concerned about the rise of black markets, which might allow rich people in certain countries to jump the line and buy vaccines for themselves and their families.
Other bio-ethicists note complicated questions around responsibility and need. For instance, countries like New Zealand have done a very good job at flattening the curve, while others like Brazil are struggling to contain active outbreaks. So should the countries that have largely stamped out Covid-19 vaccinate their populations last?
"We need to think through how to distribute vaccines to reduce harm internationally," said Ezekiel Emanuel, an oncologist and senior fellow at the Center for American Progress. "And some countries are really suffering more than others."
Within the U.S., bioethicists hope that vaccines are distributed in a centralized and coordinated way. Back in April and May, the lack of coordination from the federal government meant that states had to compete for supplies, including ventilators, and manufacturers were confused about where to send equipment.
"I'm worried that there will not be the kind of national leadership on the issue that we need to avoid fights from breaking out as people jockey to get access," said Michelle Mello, professor of law and medicine at Stanford University.
Even if the federal government steps up, there isn't yet consensus on who should get access to the vaccines first.
Most of the experts had a set of categories in mind. Lawrence Gostin, a professor of global health law and director of the O'Neill Institute for National and Global Health Law at Georgetown, helped draft policy papers on the issue for the Obama administration during the H1N1 crisis of 2009.
His strategy would be using the vaccine first to prevent further spread of the virus.
"That is, we might need a kind of ring vaccination strategy for major clusters of cases that don't we want to spread to other other cities or states," he said.
Next, he would prioritize health workers on the front lines of the pandemic. Once they're vaccinated inside hospitals, he would turn his attention to other essential workers, including police, sanitation workers, and workers who are critical to maintaining our food supply. Then he'd select the most vulnerable, including the elderly or marginalized populations or those with pre-existing conditions.
Other experts have different ideas.
Nisarg Patel, a surgeon at UC San Francisco and a co-author of an op-ed on the topic, would start with the people at highest risk, including health workers, essential municipal workers, vulnerable groups and the elderly.
But given that nearly half of Americans have at least one chronic illness, there might need to be some consideration about who gets prioritized within that group. For instance, should immunocompromised patients in the midst of cancer treatment get access to the vaccine before tens of millions of people with Type 2 diabetes?
"The way you think through them is to think through the outcomes," said Mello, although she notes the evidence is still accumulating on that. She also points out, however, that it might be the case that not everyone will want the vaccine immediately - so some might wait and see what happens with the first cohort.
Even then, it's not that simple.
Bioethicists point out that some of these decisions can only really be made once the specifics of the vaccine are better understood.
Vulnerable populations including the frail and elderly might not mount a robust immune response to the vaccine, for instance. The data on that from clinical trials is still limited. And health care workers might not get first dibs if they have sufficient PPE to protect themselves. The first round might be limited to those who treat Covid-19 patients specifically.
"A lot will depend on the vaccine, but also the modeling that we do," said Emanuel. "We might even find that the best way to reduce the spread of the virus is to vaccinate the most common transmitters, like grocery store workers or policemen," he said.
Another question that will need to be determined by committees: If sufficient people aren't willing to volunteer for a vaccine, should governments require that certain groups get vaccinated?
"Voluntary is always better," said Emanuel. "It's never the first option to mandate it, but it may be a necessary one."
Caplan agrees that discussions should be underway on this issue, as a lot of people might be reluctant to get vaccinated. Anti-vaccination sentiment is far from limited to the United States, he points out. In countries like France, surveys have shown that 1 in 3 people do not feel that vaccines are safe.
Caplan doesn't have a clear solution for hardline anti-vaxxers, who might never be willing to get the vaccine. But he does think that a lot can be done to sway those who are reluctant or hesitant by showing data from the first group that gets vaccinated. In the United States, he would message to the public that vaccination is required for certain freedoms, like travel or sending their kids to school. Emanuel suggests that public health workers might even consider teaming up with celebrities and influencers to help spread the word.
These challenges — and many more surrounding vaccine allocation — are surmountable with the right planning and coordination, Emanuel stresses.
"We shouldn't give up," he said.