Stock markets are booming, scientists are hailing Pfizer's vaccine which has shown 90 percent effectiveness and corporates are already imagining the sunny prospect of a return to on-campus work but Pfizer is reminding everyone that it still needs to check off three boxes before its silver bullet progresses toward emergency use authorisation.

Pfizer explains that there needs to be "success" in the following three areas: Evidence of efficacy in most vaccinated patients, evidence of safety with data from thousands of patients and manufacturing which is consistently at the highest quality standards.

Early Monday, Pfizer and German partner BioNTech released efficacy results from a late stage study of its Covid-19 vaccine candidate 'BNT162b2'. The company reported it was 90 per cent effective after looking at 94 infections in a study that has enrolled more than 43,000 people in the US and five other countries. Some got the vaccine, others got dummy shots.

The Phase 3 clinical trial began on July 27. Nearly 39,000 people have received a second dose of the vaccine candidate by November 8, 2020.

The next milestone for Pfizer and BioNTech is the third week of November. By then a median of 60 days of safety data will be available, as required by the FDA in its guidance for potential Emergency Use Authorization.

The Pfizer - BioNTech shot is one among 10 vaccine candidates in late-stage testing globally. Moderna, another US pharma giant, is also optimistic. Dr. Anthony Fauci, the US government's top-infectious disease expert, said today that Moderna's vaccine is also likely to work out.

In an interview with Bloomberg, William Moss of Johns Hopkins' International Vaccine Access Center laid out three questions that still need answers, despite the hugely encouraging despatch from Pfizer today: "How long does this protection last? What kind of disease did this prevent? Was it mild or severe?"

"They are telling us whether the vaccine protects against the disease, they are not telling us whether it prevents transmission."

Moss said that if people let up on masking up and social distancing thinking that the vaccine has arrived and not knowing if it stops transmission (too), the effects may be seen in rising cases as a result of letting up on proven safety behaviours.

Based on current projections, Pfizer and BioNTech expect to produce globally up to 50 million vaccine doses in 2020 and up to 1.3 billion doses in 2021.

Dr Fauci said the results of the Pfizer vaccine's 90 per cent effectiveness are "just extraordinary".

"Not very many people expected it would be as high as that. It's going to have a major impact on everything we do with respect to COVID," Fauci said in a call with reporters.

Stocks are surging and Wall Street is climbing merrily back to record heights. Although the vaccine news is not a quick fix, the reaction is one of sheer relief.

"Good for earnings, good for consumer behaviour, good all around" is the word on the street, according to Bloomberg Intelligence, during post-lunch trading in New York.

Confirmed coronavirus infections in the United States shot past the 10 million mark and more than a quarter million Americans (237,000) are dead from the virus.