Some Long Islanders told News 12 that they are having a hard time making a follow-up appointment to get their second dose of the COVID-19 vaccine.

Several people who have received the first shot say they were instructed to make the second appointment online or over the phone – but bottlenecks in the system have been causing issues.

“We're trying to set it up so we're mobilized to give as many people the vaccine as we can without overextending, making appointments that we can't meet,” says Dr. Lawrence Eisenstein, Nassau’s health commissioner. “We're sensitive to the situation that we don't know how much we're going to get tomorrow, we don’t know exactly which people are going to be eligible tomorrow. It's a work in progress, but it really has been successful.”

For Pfizer's vaccine, the second dose is given 21 days after the first. For the Moderna vaccine, the second dose comes 28 days later.

Depending on supply, Nassau health officials say some people might have to wait a few extra days for that second dose.