Smartphone applications may soon replace the scarred skin that once was used as evidence of inoculation against infectious disease.

Companies including Microsoft and IBM have been developing software intended to make it easier to determine whether someone has been vaccinated against COVID-19. But the prospect of proving one’s defenses against the global pandemic has some lawmakers and privacy advocates skittish about “vaccine passports,” a phenomenon that’s existed in some form in the United States since outbreaks of smallpox in the 19th century.

There have been no formal proposals to institute a “vaccine passport” system at any level in Washington or Idaho, though Gov. Andrew Cuomo of New York proposed a voluntary system called “Excelsior Pass” as a way to share vaccination information digitally in the Empire State.

The phrase “vaccine passport” seems to have originated from an essay written in October 1901 by James Hyde, a Chicago physician, published in the magazine Popular Science.

“Vaccination should be the seal on the passport of entrance to the public schools, to the voters’ booth, to the box of the juryman, and to every position of duty, privilege, profit or honor in the gift of either the State or the Nation,” Hyde wrote.

Some lawmakers in Washington and Idaho, staring at the prospect of restrictions being imposed for travel and other services, disagree. Residents should be allowed to determine whether they want the vaccination, and it shouldn’t be a precondition to resuming public life, they argue.

Gov. Brad Little signed an executive order last week prohibiting any Idaho “department, agency, board, commission, or other executive branch entity or official” from requiring proof of COVID-19 vaccination for access to state facilities or services, or sharing information with anyone creating such a registry. Little, in his order, called mandated vaccinations “contrary to my core values as an Idahoan and conservative,” though he strongly urged residents to get vaccinated.

In Washington, a group of 20 lawmakers introduced a bill last week that would prohibit requiring proof of vaccination to gain access to “public spaces,” defined as businesses, sidewalks, parks and more. The bill’s primary sponsor, Rep. Jim Walsh, R-Aberdeen, acknowledged that the legislation was introduced too late for a vote in this year’s legislative session, but hoped it would gain support after introduction.

“Such demands would be a violation of citizens’ civil and constitutional rights in this state,” Walsh said in a statement introducing the bill, which has attracted the local support of state Reps. Jenny Graham, Mike Volz and Bob McCaslin. “We can’t wait for courts to issue opinions on these matters. We need to clarify state law as quickly as possible.”

Gov. Jay Inslee said Friday in Spokane that there hadn’t been any proposal of a travel passport in Washington.

“I don’t think there should be a legitimate concern about that because certainly there’s been no proposal I’ve heard of in the state of Washington to have ‘a Washington state passport,’ ” Inslee said, though he noted individual businesses could decide which customers to serve.

Graham, who contracted COVID-19 last year, said her support for the legislation should not be seen as discouraging people from receiving vaccinations if they choose, but to anticipate potential problems with requiring proof of a shot or shots in certain areas of public life.

“It’s more, to me, of a pump-the-brakes thing. Just to say, ‘how well has this been thought out?’ ” Graham said.

States generally have authority to impose certain measures for public health, as seen during the pandemic with mandates on wearing masks and limiting occupancy in businesses, said Agnieszka McPeak, an associate professor of law and director of the Center for Law, Ethics & Commerce at Gonzaga University’s School of Law. That includes compulsory vaccination, as outlined in a 1905 U.S. Supreme Court case involving the smallpox vaccine in Massachusetts.

But requiring a vaccine 116 years later, and collecting that information digitally, poses a new set of problems, McPeak said.

“What makes this unique is the fact that, when we’re dealing with your personal data and information on a smartphone, there are other additional elements that come into play before something like this should be implemented,” she said.

“These are the concerns we didn’t have in the time of smallpox,” she added.

IBM is developing the Excelsior Pass, and Microsoft has announced an initiative of its own. Organizations that use such applications, be they governments, companies or something else, need to know how that data is being collected and what it’s being used for, said McPeak, who specializes in data privacy.

“We know that private companies are vacuuming up all our information,” she said.

That’s the same reason the American Civil Liberties Union has concerns about adoption of applications to track vaccination, said Jennifer Lee, manager of the Technology and Liberty Program at the ACLU of Washington.

Vaccine surveillance also poses the risk of creating a new technological system that would be subject to invasion, Lee said. It would also create the potential for “mission creep,” she said, meaning such systems could be employed beyond traditional uses, such as travel, school attendance and seeking certain types of employment, as well as be difficult to dismantle once it’s determined vaccine surveillance is no longer needed.

“Sometimes when we are rushing to do things, we make bad decisions,” Lee said, pointing to the controversial Patriot Act legislation imposed in the immediate aftermath of 9/11, provisions of which lingered in federal law for the next two decades in spite of concerns about privacy .

All of these concerns have been raised by lawmakers at the federal level, as well, even though the Biden administration announced Tuesday it would not require a centralized vaccination credential. Rep. Russ Fulcher, R-Idaho, sent the administration a letter demanding answers to several questions before any vaccine certification system were put in place, including if there would be any exemptions and how any data would be collected and shared.

There are echoes in the arguments of today’s vaccine passports from those early days of smallpox vaccinations. A member of an early “anti-vaccination league” in Spokane wrote The Daily Chronicle in September 1899, arguing against compulsion of a vaccine to re-enter everyday life.

“This is the country of free thought and speech, is it not?” wrote Lida M. Ashenfelter in a letter to the editor, before launching into an argument containing many of the points common among vaccine skeptics throughout the ages: doubting their efficacy, concerns about cost and that the vaccine was developed from the udder of a cow, “a much lower order of creation.”

In a scathing rebuke of the anti-vaccination leagues published in the paper 17 days later, Dr. E. D. Olmsted pointed to a vast reduction in smallpox deaths overseas after the introduction of vaccines.

“If the anxious parent who has seen a typical vaccination sore will imagine his child covered with a multitude of such sores, invading even the mouth, nose and ears, he will form some idea of the amount of suffering endured by a patient with unmodified smallpox,” the doctor wrote.

Beyond personal choice about receiving the vaccine, setting up a checkpoint system runs the risk of discriminating against portions of the population that may not yet have access to vaccines, Lee said. Early and incomplete data on the vaccine rollout in the United States reported by the Centers for Disease Control and Prevention show a large portion of the vaccine has been delivered to white, affluent people, and requiring vaccines at this stage could continue to pose equity problems, Lee said.

“Who you would be disproportionately excluding are already the most vulnerable in society,” she said.

For that reason, the ACLU is pushing for equitable distribution of the vaccine to quickly reach herd immunity, the level at which enough of the population has been inoculated to protect those who haven’t been, she said.

“Once we do reach herd immunity, I don’t think a COVID vaccine passport will be as urgent, or seem as urgent,” Lee said.

Staff writer Arielle Dreher contributed to this report.