A Massachusetts software developer’s Twitter bot offered help to those seeking vaccine appointments at a time they were frustratingly scarce. Now he’s shut it down, and hundreds of people are saying thank you.

The vaccine time bot checked around 20 vaccine appointment websites in the state every minute and tweeted out where appointments were available.

Developer Dan Cahoon tweeted on Wednesday, referring to the state’s vaxfinder.mass.gov website

“With vaccines now readily available in Massachusetts I’m going to turn off vaccine time.”

The tweet garnered more than 230 replies by midafternoon Thursday, with many saying they had used the bot to get not only themselves but others vaccinated. The replies reflected the tense times the state saw when vaccines were first made available but there wasn’t enough supply to meet the demand. According to Cahoon, a software developer at Ginkgo Bioworks

“It’s really great to see how many people it was able to help. It’s super-heartwarming to see all the people replying and saying they’ve been able to get appointments through this tool. … It’s been amazing.”

He said he developed the bot in his spare time after watching colleagues struggle to find appointments on the multiple websites where they were listed.

“Basically, it involved going to various websites, refreshing the page for hours on end. … Overall it ended up being a lot of wasted time. I’ve done some amount of bots before mostly for my company and I thought, ‘Hey, I could probably code this up pretty quickly. Anybody who followed the Twitter [feed] had a little bit better of a chance of getting an appointment when it was available.”

While media outlets earlier this year included bots in their lists of tips on how to get a vaccine appointment, some critics have said they gave the tech-savvy an advantage. Cahoon said he felt his bot levelled the playing field between people who only had limited time to search for appointments and people who had the time to sit at the screen for hours clicking away. He noted:

“Hopefully, it brought a little more fairness to the system.”

He also said the reasons he chose Twitter included the ease with which people can sign up and can get notifications on their phones.

Cahoon said that if the unthinkable happens and there’s another pandemic, it would be better if there was a single website people could go to and pre-register. That would allow a fairer distribution of the vaccines and eliminate the “problem where people have to spend a lot of time looking for them,” he said.

After enduring the early frustrations, the state is now a national leader in vaccinations, with more than 4.5 million people with first shots and nearly 3.9 million fully vaccinated as of Thursday.

Safe and effective vaccines are free for people who live, work, or study in the state. People 12 to 17 can receive the Pfizer vaccine. People 18 and older can receive either the Pfizer, Moderna, or Johnson & Johnson vaccine, the state says.