"It's not a magic bullet. You can't vaccinate your first frontline border worker and then expect to just give up on everything else. You've got to keep this up until you've actually beaten this thing back," she said.
"It's still out there. There are still places really struggling with the disease, so you've just got to be aware of that."
Millions of people around the world have already received the Pfizer vaccine, which does not contain any live virus.
"That means that people who have got quite compromised immune systems are not at risk of a live virus replicating," Petousis-Harris said.
"You cannot get Covid or anything from these vaccines, so they're going to be very safe for pretty much everybody."