a competing design for exposure tracing.
In this instance, the British government may be overmatched by the Silicon Valley titans, which control the software that runs on nearly every smartphone on the planet. Unless Britain changes course, the companies are refusing to provide access to a Bluetooth signal on iPhones and Android phones that is needed to measure proximity.
That has left Britain with a stark choice: either alter the design or risk releasing an app with major technical flaws.
At its heart, the debate is about balancing public health and individual privacy. In Britain, which has a history of robust government surveillance to fight terrorism, officials say that more can be learned about the virus by collecting lots of information in a centralized database. They argue this will provide more research capabilities to spot emerging hot spots and patterns of how the virus spreads.
By contrast, Apple and Google are promoting a decentralized approach that would protect against invasions of privacy. But the government says that privacy considerations are only part of a complex calculus it is trying to navigate.
“If privacy was the only thing that we were optimizing for then it may be that a decentralized approach should be the default choice,” Matthew Gould, the head of NHSx, the division of the National Health Service that is building the app, said in a House of Commons hearing this week. “But actually we’re balancing a number of things.”
The British authorities said that the data would not include personally identifiable information, and that access would be limited to those working on the pandemic response. A committee in Parliament has called for legislation creating privacy protections around the app.
In opposing Britain’s effort, Apple and Google are supported by academics, security researchers and privacy groups that want to restrict government data collection, saying that, whatever the safeguards, a centralized database creates too much potential for abuse. Britain’s top privacy regulator, Elizabeth Denham, said last month that a decentralized model should be a “starting point” for contact tracing.
“It is vital that, when we come out of the current crisis, we have not created a tool that enables data collection on the population, or on targeted sections of society, for surveillance,” a group of more than 170 scientists wrote in an April 29 statement opposing the British app’s design.
To enforce their view, the companies will provide important access to a phone’s Bluetooth signal only to tracing apps that store health information on a person’s smartphone. This prohibits data from being uploaded and stored on government servers.
Many have raised additional concerns that the British app allows self-reporting, a feature that could easily be abused.
There are signs that Britain may be bending to the criticism. Mr. Gould told Parliament this week that the government was continuing to speak with Apple and Google, and that the country could change its approach.
The health service awarded a contract to a Swiss company, Zuhlke Engineering, to “investigate” building a tracing app using the Apple and Google specifications, according to documents obtained by the research firm Tussell and first reported by The Financial Times.
It would not be first time Britain had taken an alternative path in responding to the coronavirus, before changing course. In March, as many countries began to shut down, Britain kept schools and businesses open, before increasing deaths and infection rates eventually led to a lockdown. Britain now has one of the highest death tolls in Europe.
Widespread testing and contact tracing are universally cited as critical steps to restarting economies without reigniting the epidemic.
Apps are designed to significantly speed up contact tracing by quickly identifying people who are most at risk of infection. The technology works by using a smartphone’s Bluetooth signal to measure proximity to nearby devices.
After an infected person shares the information on the app, anyone they have had close interactions with will receive an alert with instructions to self-isolate. A log is kept of the phones of people who have come within a certain distance of each other, like those sitting next to each other on a bus or subway.
Britain began testing its app this week on the Isle of Wight, an island off the southern coast with about 140,000 people. As the country struggles to perform enough virus tests and provide protective gear for health workers, leaders are trumpeting the app as progress.
Ian Levy, of the National Cyber Security Center, likened the technology to John Snow, the scientist who in 1854 traced a cholera outbreak in London to a contaminated water pump. The British health minister, Matt Hancock, said citizens who downloaded the app would be doing their “duty.”
After people report symptoms through the app, their information will be sent to the N.H.S. It will then perform an automated risk assessment to identify other app users who may have come into contact with the infected person.
But critics say the British app will not work effectively unless it uses code provided by Apple and Google. In Australia, an app with a similar design has been criticized for technical problems. Germany recently reversed to support the Apple-Google specifications. Austria, Italy and Switzerland are using it as well.
Britain is moving forward with its app despite a lack of evidence that any tracing technology will help fight the virus without widespread testing, an area where the country has lagged behind others in Europe. An added challenge is that useful technology needs a huge portion of the population to participate. A recent study by epidemiologists at Oxford University estimated that, to be effective, 60 percent of the population must use the app, a figure on par with omnipresent apps like WhatsApp. (Mr. Gould differed with that estimate, saying that even 20 percent would be useful.)
Carly Kind, director of the Ada Lovelace Institute, a policy research group focused on technology, said prematurely releasing an ineffective app would undermine public trust. “A bad app is definitely worse than no app,” she said.
Luciano Floridi, director of the Digital Ethics Lab at Oxford University, warned against “looking at technology as the savior,” when a pandemic requires broader public health and medical solutions. He said more testing and thousands of human contact-tracers were needed to track the disease.
“This will be a small component in a much larger approach,” said Mr. Floridi, who is on a government advisory board related to the app. “Hopefully, it will not do any harm.”