Amidst rising COVID-19 cases, Connecticut officials saw cause for optimism Monday as Pfizer, a drugmaker with a presence in the state, announced its new vaccine is believed to be 90% effective at preventing the coronavirus.

“Connecticut’s very own Pfizer along with BioNTech has created a vaccine that has had very good, strong, positive results in the early trials. Ninety percent effective. More effective than we had probably anticipated before,” Gov. Ned Lamont said during a briefing on the state’s COVID-19 situation.

Pfizer, which has a research facility in Groton, announced the results of its clinical vaccine trial Monday. John Burkhardt, Pfizer senior vice president of drug safety research and development, joined Lamont remotely for the press briefing. He said about 200 Groton employees worked on the vaccine project.

Burkhardt said the company is hoping to have preliminary approval from the Food and Drug Administration in a matter of weeks. The goal is to make up to 50 million doses of the vaccine before the end of the year. The vaccine requires two doses to be effective, so 50 million doses would be enough to immunize 25 million people. Lamont estimated that Connecticut could receive roughly 1% of the vaccines created.

During the press conference, Lamont sought both to persuade the public of the vaccine’s effectiveness and caution residents against letting their guard down.

“Look, we’re trying to present the science as we see it. It’s good news. It’s going to take many months to roll out and all the precautions we can take in terms of masks and distancing in the meantime will make a world of difference,” he said.

The governor pointed to the state’s COVID-19 numbers since Friday. Another 3,338 residents tested positive for the virus at a rate of 3.7%. Hospitals admitted 94 more coronavirus patients, bringing the state total to 496 hospitalized patients. Meanwhile, 27 additional residents died of the virus over the weekend.

“Don’t think this is a milder form of COVID with less fatalities. I’m afraid you’re seeing the fatalities ramp up again around the country following higher infection rates,” he said. “Don’t take anything for granted.”

In the near term, the state is working on a plan to distribute the vaccine when it becomes available. Dr. Reginald Eadie, president and CEO of Trinity Health of New England and co-chair of the state’s vaccine advisory panel, said the state would prioritize inoculating health care and frontline workers as well as elderly people and vulnerable populations.

However as more doses of the vaccine become available, the state will need to shift gears and attempt to convince residents, some of whom are skeptical of vaccines, that the treatment is safe and effective. Eadie said his group is working on a communication plan to encourage participation.

Burkhardt said Pfizer’s history should give patients some comfort. He said the company has been in the vaccine business for years.

“No corners were cut. We followed this tried and true methodology that has worked so well for us in the past and continues to deliver superior and safe products,” Burkhardt said.

Asked whether the state would consider requiring residents to get a COVID-19 vaccine, the governor said, “No.”

“That’s not the way I’m thinking about it.” Lamont said. “I think by far the best way to do this is on a voluntary basis.”

Near the end of the press conference, Eadie and Burkhardt were asked to speculate on the historic nature of the looming COVID-19 vaccine distribution process. Neither was willing to offer a guess as to whether it would be the largest such effort in history. The governor, on the other hand, was willing to go out on a limb.

“I’m a politician. We always speculate. My strong instinct is this is by far the largest vaccination effort in the history of the world,” Lamont said.