Businesses and governments are developing COVID-19 vaccine certifications that let people prove they’ve been immunized so they could enter spaces or travel without as much worry that they’d get sick or pass the virus to others. Conservative politicians recently seized on these efforts as evidence of government overreach, while other people argued the certifications a more benign public health tool — one that’s analogous to strategies we’ve uses to manage disease for decades.

“Usually, the reality is somewhere in the middle, and that’s the case for this as well,” says Lisa Lee, director of the division of Scholarly Integrity and Research Compliance at Virginia Tech.

There’s a reason these types of tools feel familiar. Using proof of vaccination to enter a country or participate in certain activities is nothing new: many African and South American countries require visitors to get yellow fever vaccines before they arrive. In the US, many people have to get a flu shot for work, and certain vaccinations are required for people to attend schools and colleges.

But there are a few things that make the proposed COVID-19 certifications different from these familiar guidelines. They may not be the government overreach boogeyman raised by many conservative politicians, but there are lingering ethical questions around them.

For one, the shots aren’t easily available to most people in the world. Many high-income countries have vaccinated tens of millions of people, while lower-income countries have secured far fewer doses. In countries like the United States, which has enough vaccine doses for all adults, lower-income and non-white people are less likely to be able to access those shots.

“What we’re going to have at least for the next year or probably two is a very inequitable distribution of vaccines,” says Chris Beyrer, a professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health. Requiring a COVID-19 vaccine certification to enter a country could be discriminatory if most people aren’t able to get vaccinated, Beyrer says. “People in wealthy countries with access to vaccines will be able to move around the world again, and the world’s poor or people in low- and middle-income countries are going to be trapped.” The past year has shown that pandemics are more of a burden on some groups than others, and this could risk adding to that existing inequity.

Even where vaccines are more plentiful, there are still quandaries around using vaccine status as a permission slip for work or other activities. In the United States, COVID-19 vaccines are also not fully approved by the Food and Drug Administration (FDA). They’re available under an emergency use authorization, a slightly lower standard that lets the agency sign off on a product when there are no other options available and the benefits outweigh the risks. Companies are still studying these vaccines. While there aren’t major concerns about the vaccines available in the US, there’s still a lot we don’t know about them. The quasi-experimental nature of these vaccines makes mandating vaccinations ethically complicated, Beyrer says.

Unlike other vaccine certification programs, these new vaccine passports are not just on the table for things like travel or school admissions — which officials use to stop a disease from spreading to a new place and to make sure students are protected. Instead, many businesses say they’re going to ask people to show their vaccination status to do things like attend a sporting event. That’s something different from any other vaccination credential strategy used normally in the US, Lee says. “This is not a brand new concept, but the issue that makes it so unusual is that it’s something you’d have to do for admittance into a daily event. That’s not something we’re used to doing,” she says.

It’s not surprising for people to be concerned about those plans, Lee says, even if they could help make sure in-person events don’t become superspreaders. She thinks the fears of government officials stopping people on a whim to demand they show proof of their shots is probably overblown. The Biden administration has stressed that there won’t be a federally mandated or centralized COVID-19 vaccine credential. But this is a new way to use vaccine information, and it’s not out of line for people to express discomfort with it, Lee says.

Some of the concerns around COVID-19 vaccine certifications are temporary. Eventually, the shots will be more widely available, and the equity issues won’t apply in the same way. The FDA will also officially license COVID-19 vaccines at some point. After we cross those two checkpoints, a COVID-19 vaccine certificate requirement to enter a country would actually be analogous to a yellow fever certificate, Beyrer says. When the FDA licenses the vaccines, asking people who work in a hospital to show that they’ve been immunized would more closely resemble flu shot requirements.

By the time that happens, though, the pandemic may no longer be in the emergency phase. When the spread of the virus subsides around the world, vaccine certifications may seem less necessary and be less justifiable in some cases. If there’s very little coronavirus circulating in a community, it’s less of a risk that someone at, for example, a sporting event might catch or carry it. The next few months are probably when they’d offer the most protection. But unfortunately, that’s also the time frame when the shots will be the hardest to get, Lee says. “It is a little bit of a paradox that when we would want it the most, it’s the least ethical to do.”