HALIFAX -- Nova Scotia's vaccine-booking system is back up-and-running a day after it crashed in heavy, first-day traffic, but now all of the first-round appointments for those older than 80 are taken.

More clinics are coming and the people who run the system say steps have been taken to make sure the surge doesn't happen again.

If it wasn't so frustrating, it might almost be funny for Kevin Potter, trying every avenue to book COVID-19 vaccines for his 90-year-old father and 88-year-old mother, who marked their 70th anniversary last September.

Last week, they got letters from the health department inviting them to book their shots.

The process didn't go well for Potter, who figures he hit redial and refresh hundreds of times, starting at 7 a.m. Monday morning.

"Yesterday was about six hours, and I never talked to a person," Potter said. "I did get through on the website, but it froze."

It turned out to be the same experience for thousands of Nova Scotians, who flooded the booking site and the phone lines as soon as they opened.

"First, we want to apologize to Nova Scotians," said Dr. Kumanan Wilson, the founder of CANImmunize.

Alarmed by the amount of online traffic, the company responsible for the website took it offline to install some queuing software.

"Well the risk is that the site would fully crash and that the recovery time would take much longer," Wilson said. "We didn't want that to happen."

Despite the challenges, the 2,200 available spots at four clinics booked up quickly.

That doesn't make sense to people like 81-year-old Gerard Gagnon, who feels he wasted his time trying to get in.

"And surely, people from Yarmouth and from Sydney certainly wouldn't be calling Halifax to book an appointment," Gagnon said.

Acknowledging the first four clinics are fully booked, the province says six others will open shortly, and bookings are now being accepted for them.

In the meantime, officials say vaccine supply is a major wildcard in the process, and more clinics will open as more supply becomes available.

That aside, the province's top doctor isn't expecting future booking problems.

"But certainly, it has been fixed, and now steps have been out in place, as we talked about, to protect that site," said Dr. Robert Strang, Nova Scotia's chief medical officer of health.

So, for now, the province is urging patience as it works its way through its portal problems -- a commodity that's starting to get in short supply itself as the pandemic wears on.

Strang says it's possible some of the traffic yesterday were people simply calling and clicking to "test" the system, but acknowledged there are people out there who might just want to make it crash for fun.

He says the province is also looking at the possibility of sorting the first batch of 80-plus Nova Scotians by month of birth or by last name, to minimize the chance for another big surge.