At hospitals across New York City, people seeking COVID-19 vaccines abruptly had appointments canceled due to what's being called a sudden change in supply. 

Thousands of others with appointments at state-run sites were informed their appointments had never been authorized.

A state official says, "An unpublished scheduling link was shared without authorization on social media…We are currently contacting everyone who used the unauthorized link to inform them of the situation.”

The cancellations are the latest snag in a rollout plagued with hiccups.

New York state's vaccine portal warns there are just 300,000 weekly doses for 7 million eligible people; 5 million just became eligible in the past three days.

In New Jersey, 4.5 million people became eligible for the vaccine this week despite having nowhere near that many doses available.

The state is also trying to explain why an extra dose of vaccine in five-dose vials is being thrown away. They say syringes leave different amounts of waste, and some vials are being tossed with an extra dose.

But doctors had no way of knowing that in advance and, sometimes, they had no one left to give the surplus doses to. The state is now belatedly telling them that rather than throw the extra doses away, they should give them to anyone, even if they're not technically eligible.

In Connecticut, vaccine rollout was also uneven. Many smaller districts were vaccinating for days before three of the larger ones managed to open.

Dr. Amna Husain, a News 12 medical contributor, says despite the flawed rollout, there's still time for the states to get this right.

“Trying to think outside the box, think on bigger scale, think on more efficient scale. Those are things I think we now know would be most helpful,” he says.