By ARIELLE MITROPOULUS, ABC News

(NEW YORK) — Although the pace of the coronavirus vaccine rollout seems to be picking up across the country, many Americans have been left frustrated by their inability to secure an appointment. With limited vaccine supplies, and very high demand, state-run websites have been overwhelmed, even crashing at times, as millions attempted to log on at the same time.

In Massachusetts, 50,000 new COVID-19 vaccination appointments that became available Thursday were “nearly filled” within 90 minutes of their release, the state reported. Meanwhile, many queued up in a “digital waiting room,” some being told that they could be waiting for hours.

Seniors in Illinois have reported spending hours on the phone trying to find an appointment, and in Washington, D.C., Mayor Muriel Bowser reported that the Capitol’s vaccine site was experiencing delays on Thursday, after all new vaccination appointments were booked, following an eligibility expansion to include people with preexisting conditions such as severe obesity.

However, an online tool launched earlier this week is hoping to ease some of the burden of finding an available vaccine appointment.

The online portal, called VaccineFinder, which has won the support of the Centers for Disease Control and Prevention, is the brainchild of Dr. John Brownstein, chief innovation officer at Boston Children’s Hospital and an ABC News contributor, who runs the site in partnership with Boston Children’s and Castlight Health.

The goal of the online portal is to assist an already taxed and underfunded public health system in the drive to inoculate.

“The idea here is to provide, at the national scale, a source of truth, in terms of where the vaccine is in communities, and create a jumping off point for people to figure out where to go, when to go, to figure out specific details of hours of operation, and therefore, at least reduce one step in people’s search for vaccines,” Brownstein said.

The website was initially created by Brownstein and his team nine years ago, following the 2009 H1N1 flu pandemic, when people were eager to be vaccinated against the disease.

“Of course, everyone wanted it, and there was a need to help bring clarity to consumers about where the vaccine was in the community,” Brownstein said.

Although initially built for the flu, the platform began to include the availability of a range of vaccines, such as shingles, HPV or travel vaccines.

When coronavirus emerged and it became clear that a vaccine would be available, VaccineFinder’s technology was updated and rebuilt to create a COVID-19 vaccine website.

“Essentially, since December, we’ve been operating where vaccine providers register with our system, and also put in their daily inventory information, so we have clarity on where all the supply is at the provider level for the country,” Brownstein said.

The website is not a one-stop shop for people to find and book appointments, but rather an intermediate step that allows users to see all the vaccine providers in their area, and see which ones have slots available for appointments.

The site works in conjunction with the national pharmacy program to display pharmacy and drugstore chains that are receiving vaccines from the federal government. It currently includes vaccine availability statuses at 20,000 locations across the country.

However, in Indiana, Iowa, Tennessee and Alaska the platform is already offering information on where residents can locate vaccines at their local hospitals, clinics and public health sites.

New York and Illinois will be added to the mix in the very near future, Brownstein said, and eventually, all 50 states.

If the website is successful, Brownstein and his fellow developers hope to expand its capability to reach vaccine providers across the country.

To date, states have administered over 66 million coronavirus doses.

As of Wednesday, 17.3% of adults have received one or more doses, and 7.9% are fully vaccinated, according to the CDC. Nearly 50 million total coronavirus doses have been administered since Jan. 20, marking the halfway point of President Joe Biden’s goal of administering 100 million doses in his first 100 days in office.

Although Brownstein said the site will not solve all the issues encountered by states, he hopes the tool will at least improve users’ experiences in their quest to find a vaccination appointment.

“What we’re hoping to do is to remove at least one or two steps in people’s really painful journeys in finding vaccines. And over time, we are going to keep adding features to provide the best possible experience,” Brownstein explained. “By improving convenience, you can drive uptake. Anything we can do to make it as simple as possible, the greater the chance that someone will get this vaccine.”

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