Editor’s Note: This story has been updated to reflect the rate of new cases in Austin and Travis County has doubled.

AUSTIN (KXAN) — Health officials are cautiously optimistic about recent news that a COVID-19 vaccine could be up to 90% effective, they said during an extended update briefing with reporters Monday.

Austin-Travis County Interim Health Authority Dr. Mark Escott said while the news is encouraging, he wants to be careful about overreacting to efficacy numbers while the trial is ongoing.

“I don’t think it would be anywhere around 90%, but we could get lucky,” Dr. Escott said.

He also said that it will probably be next year before the vaccine is available for healthcare workers and first responders, but late December this year is still a reasonable time the vaccine could be ready to go.

Positivity rate in the area has gone up quite a bit, Dr. Escott said. For the week ending Oct. 24, the Austin-Travis County COVID-19 dashboard said the positivity rate was 3.8%. Dr. Escott revealed the most recent positivity rate, measured a week ago, is 5.2%, and it seems to be widespread between people ages 10-59.

“So we have significant increases, in transmission, which means that we have to reenergize our efforts to act in protective ways,” he said. “It’s important now that we put a lid back on this, that we drive the numbers back down in advance of Thanksgiving, which right now the projections are showing is going to continue to get worse.”

The rate for new cases has doubled in a little more than a month, data shows. Dr. Escott said the area had an average of 64 new cases on Oct. 4. On Sunday, the area reported the seven-day average of new cases at 135.

“We have seen a substantial increase in our cases in the last month, in particular over the past week,” he said.

As of now, flu cases are low, Dr. Escott said, but he still recommends everyone get a flu shot to keep it that way. In fact, right now, flu cases are the lowest they’ve been in the past four seasons, he said. APH Chief Epidemiologist Janet Pichette said the agency was able to administer around 400 flu shots in a drive-thru event over the weekend, and she called the event a success.

“The best way to take flu out of the mix all together is to get your shot,” she said. “We felt like it went very effective, there were definitely lessons learned through that drive-thru exercise, but we continue to practice and refine so that when we do have the opportunity to deliver the vaccine to the community, we can do it as timely and efficiently as possible.”

When asked about President-elect Joe Biden’s potential COVID-19 plan once he gets into office, Dr. Escott said it’s going to take a lot to make a federal mask mandate work because he’s got to convince everybody to get on board with one.

“There’s work to be done,” Dr. Escott said. “We have to continue to work hard to convince those who haven’t been convinced that the threat is real.”