President-elect Joe Biden, who has announced a team to shape his Covid-19 plan, on Monday called Pfizer’s announcement of vaccine test success as “excellent news” but said masks remained a “more potent weapon against the virus”.

Biden, who had made fighting the pandemic his top priority, named a 13-member advisory board on Sunday to “shape my approach to managing” the surge in cases and the search for vaccine. It is co-chaired by former Surgeon General Vivek Murthy, former head of the Food and Drug Administration (FDA) David Kessler and Yale School of Medicine’s Marcella Nunez-Smith.

Biden’s transition team was informed of Pfizer’s vaccine, which the company said has proven to be 90% effective, just hours later. “Last night, my public health advisors were informed of this excellent news,” he said on Monday. “I congratulate the brilliant women and men who helped produce this breakthrough and to give us such cause for hope.”

But he cautioning the end of the battle against Covid-19 was “still months away”. It will be “many more months” before a vaccine is widely available. This is why, he said, citing Centers for Disease Prevention Director Robert Redfield, “for the foreseeable future, a mask remains a more potent weapon against the virus than the vaccine”.

“Today’s news does not change this urgent reality. Americans will have to rely on masking, distancing, contact tracing, hand washing, and other measures to keep themselves safe well into next year. Today’s news is great news, but it doesn’t change that fact.”

Biden had withstood ridicule for his use of masks and strict adherence to social distancing norms during the campaign.

President Trump, who has not conceded the election and is challenging the outcome, welcomed the announcement in a tweet in all-caps: “STOCK MARKET UP BIG, VACCINE COMING SOON. REPORT 90% EFFECTIVE. SUCH GREAT NEWS!”

Vice-President Mike Pence, who leads the White House task force on Covid, was equally effusive. “Thanks to the public-private partnership forged by President @realDonaldTrump, @Pfizer announced its Coronavirus Vaccine trial is EFFECTIVE, preventing infection in 90% of its volunteers,” he tweeted.