Lauren Buck’s days start early, compiling the names of people in Revere who have tested positive for COVID-19. The calls begin a few hours later and often last until 8:30 or 9 at night.

“There are a lot of people who are very, very cooperative and there are people who can be very scared or sometimes don't understand,” said Buck, the director of public health in Revere and part of the city’s three-person team doing contact tracing.

As COVID-19 surges across Massachusetts, local boards of health and the state are beefing up their contact tracing teams. This labor-intensive work has been a major part of the state’s response to the virus.

The idea behind contact tracing is simple. Anyone who has tested positive — or has come into contact with someone who’s tested positive — for the virus is called and told how to isolate or quarantine themselves so they don’t infect anyone else. Revere officials consider the program a critical part of the city's COVID response,and they’re expanding the team. The same is true in lots of other communities.

The state is also increasing its contact tracing capacity to back up local boards of health. The team is 1,300 strong right now, and the Contact Tracing Collaborative (CTC) said it’s actively recruiting another 800 people.

But as efforts across the state ramp up, there are skeptics. In fact, some experts say this multi-million dollar initiative isn’t helping — and it might actually be hurting the state.

“The proof is right in front of us. It clearly didn't work,” said Michael Mina from Harvard’s School of Public Health. “We have exponential growth that's out of control.”

Mina argues that contact tracing can work in certain contexts, such as with Ebola or HIV, or very early on in the pandemic in South Korea. However, he said, “we've never seen any real data from the U.S. that this can work.”

He pointed to a recent study in the medical journal JAMA that highlighted some major limitations of contact tracing, including the timeliness of contract tracers’ calls and how many cases contact tracers are actually catching compared to all of the cases out there.

“I actually think the insistence on contact tracing and making that a cornerstone of our response is part of the reason we're in the problems that we have right now,” Mina said.

Through September, Massachusetts had spent $66 million on contact tracing.

Mina thinks that kind of money would be better spent on a massive testing program. He’s a leading advocate of rapid, at-home testing. Not only is the focus on contact tracing draining resources, he believes, it’s preventing the state from thinking more creatively about its response. And some states — including Maine and New Hampshire — are scaling back their contact tracing as they are swamped by COVID cases.

Some predicted this.

“Because it's resource intensive, it diverts public health efforts from other activities,” said Marc Lipsitch at the beginning of the pandemic when the CTC, with the nonprofit Partners in Health, was first launched.

Lipsitch, who is also at Harvard’s School of Public Health, warned against investing heavily in the program.

“Contact tracing works well when you have relatively few cases, so you have the resources to do it, and when you have even fewer cases that are unknown, so testing capacity is high relative to the case burden. Neither of those is true,” he said.

Lipsitch said contact tracing can be useful in limited settings like nursing homes, but not for a whole state.

But both Mina and Lipsitch acknowledge they are in the minority among public health researchers and officials. Many experts believe there is value in contact tracing, saying it helps identify clusters, understand how the virus moves through society and stop chains of community transmission.

Buck in Revere said contact tracing does something else, too. It connects those in isolation or quarantine with resources.

“Many times people are worried about food, and we have a really good infrastructure in Revere in terms of getting food to people,” she said. “A lot of times we hear worries about paying bills.”

Buck said her team’s phone calls are a way of being there for their community when things are hardest.