OTTAWA -- Ottawa Public Health says it is monitoring news about a vaccine for COVID-19 closely and is "cautiously optimistic" about Monday's announcement from Pfizer.

Pfizer said Monday that early results from its vaccine trials suggest the shots may be 90 per cent effective at preventing COVID-19.

In a statement to CTV News, Ottawa Public Health said Pfizer's announcement was promising, but urged that it doesn't mean the pandemic will be over right away.

"This week’s news from Pfizer’s first set of results of its phase 3 vaccine trial is promising initial evidence that work on this from the scientific community is advancing," the statement said. "While cautiously optimistic, there is still much work to do to and we are likely months away from a vaccination campaign."

Ottawa Public Health noted that the Public Health Agency of Canada and the Ministry of Health would take the lead on any significant decisions about a COVID-19 vaccine in Canada. The Ontario government is in charge of setting the strategy for local public health units, but OPH is preparing for an eventual vaccine rollout.

"Informed by its extensive experience in previous vaccination campaigns, OPH has begun to consider its future approach, including adapting to new COVID-19 protocols, such as what has been implemented for flu vaccine clinics this year: allowing for physical distancing before, during and post-immunization, increased sanitation protocols, and more," the OPH statement said.

Prime Minister Justin Trudeau called the news about Pfizer's possible breakthrough a "light at the end of the tunnel" but he urged Canadians to continue practicing public health measures to limit the spread of COVID-19 until an effective vaccine is actually available. 

Ottawa Public Health shared the same message.

"Until use of a vaccine provides widespread immunity to interrupt community transmission, OPH reminds everyone that prevention is our best tool to minimize COVID-19 transmission in the community," OPH said. "We know that wearing masks, physically distancing at least 2 meters from anyone outside our household and staying home while sick significantly reduces the rates of transmission in Ottawa, and we ask the public’s cooperation in these continued efforts."

Pfizer cautioned that the protection rate might change by the time the study ends, saying such early data is highly unusual.

With files from CTVNews.ca's Rachel Aiello and The Associated Press.