KITCHENER -- Waterloo Region's new vaccine booking system had some delays as second dose eligibility opened to more residents.

New system had wait times of more than an hour on Wednesday morning.

The region's website was briefly down. Officials tweeted it was working again around 10:45 a.m.

By Wednesday night, there was no longer a wait.

They asked people to "continue to be patient" when booking their appointment.

The system eliminates the need to pre-register for a vaccine, instead allowing residents to schedule a first dose appointment as soon as one is available.

People aged 12 and older are eligible to use the self-serve option to book their first dose appointment. They no longer need to pre-register for a vaccine.

Anyone eligible for an accelerated second dose will also be able to rebook using the new system.

Public health officials encourage residents to check all clinic locations for appointments, saying more spaces will open over the next week.

Clinics are open to anyone who is currently eligible to book a first or second dose.

Confirmation texts and emails may be delayed due to high volumes of users, public health officials said.

Terry Yantzi, the region's director of information technology services, said Tuesday at a Committee on the Whole meeting that the new system is designed to allow users to book the first available vaccine appointment. However, that functionality only works when the system has capacity.

He added the booking button may not appear if there are a lot of users in the system. If that's the case, people will need to search individual clinics for available appointments.

Yantzi warned the new system might be very busy on Wednesday as more people become eligible for a second dose.

"We expect a large number of people coming to the system, so there might be considerable load on the system in the next 24 to 48 hours after we make the change to the system Wednesday morning," he said.

Starting Wednesday, second doses will be available to anyone who received their first mRNA dose on or before May 30.

Local pharmacies and primary care providers are also administering vaccines in the region. Appointments can be made directly through those locations.

Previously, people needed to fill out a form to request an earlier second dose. Officials said anyone who used that form should be invited to book an appointment on Tuesday.

Officials continue to encourage everyone to take the first mRNA vaccine available, adding it's OK to mix Moderna and Pfizer for first and second doses.

The system will also cancel a prior appointment once a new one is made.

Waterloo Region's COVID-19 task force is now administering as many as 9,000 shots in a day.

Walk-in clinics for first doses also launched Wednesday at three clinic locations.

Health Sciences Campus Vaccination Clinic

10 Victoria St. South, Kitchener

Monday to Friday: 1 to 4 p.m. and 5 to 8 p.m.

Saturday and Sunday: 9 a.m. to 12 p.m. and 1 to 4 p.m.

The Boardwalk Vaccination Clinic

435 The Boardwalk, Medical Centre 2, Suite 106, Waterloo

Open 7 days a week: 8 a.m. to 8 p.m.

Waterloo Region Public Health

99 Regina St. South, Waterloo

Open Saturday and Sunday: 9 a.m. to 12 p.m. and 1 to 3:30 p.m.