New York: Pfizer, which has struck a nearly $2 billion deal with the US government to deliver 100 million doses of a COVID-19 vaccine developed in collaboration with its German partner BioNTech, is hoping to seek regulatory approval for a vaccine "as early as October" this year and have a vaccine on the market by year end.

A "best case scenario" would be approval before year end and a vaccine by year end, according to Pfizer.

"In the third quarter of this year, we hope to get into the hospital setting with a drug that is given intravenously to patients hospitalised with COVID," John Burkhardt, senior vice president, Drug Safety Research and Development at Pfizer, said at a news conference in Connecticut Wednesday.

"An interesting thing about this vaccine approach is that the mRNA is enclosed in a lipid nanoparticle, so you can imagine the complexity of that. At this site, we are looking at engineering that particle and analyses for it that will allow clinical trials as well as the manufacturing to occur," Burkhardt said.

He promised Americans "safety will not be compromised" in vaccine development. "We are very optimistic", he said.

Americans will receive the vaccine for free and the US government can acquire up to an additional 500 million doses. Pfizer and BioNTech said in a statement they could potentially produce more than 1.3 billion doses by the end of 2021.

"Pfizer is one of the leading horses in this race right now. There may be several winners. We need several winners," Connecticut Governor Ned Lamont said at a news conference Wednesday.

Pfizer's Groton, Connecticut facility has a long history of drug discovery and development including Zoloft and Zithromax.

Pfizer's vaccine candidate will now go into large scale clinical trials involving 20,000-30,000 patients before end July. It must be proven effective and receive emergency authorisation before it can be distributed.

Pfizer is finishing an earlier stage of testing to determine which of four possible candidates to try in the final study.

Preliminary data from studies have shown a good immune response from vaccinated patients, Pfizer scientists told reporters.

Pfizer and BioNTech are evaluating at least four experimental vaccines, each of which represents a unique combination of messenger RNA (mRNA) format and target antigen.

Pfizer received fast track status for two of four vaccine candidates last week based on preliminary data from ongoing Phase 1/2 studies in the United States and Germany.

Explaining the nuts and bolts of the "fast track" label, Burkhardt said the new status allows straight line access to US health authorities.

"You don't sit around and write a 100-page document, send it for review, wait 45 days for the outcome. You can be on the telephone in real time," Burkhardt said.

Pfizer said an oral treatment for COVID-19 patients is also on its longlist.

Meanwhile, Pfizer hopes to have antiviral medication ready for clinical trials in August or September.

Also next week, a vaccine created by the National Institutes of Health and Moderna Inc. is ready to begin final-stage testing in a study of 30,000 people.

US President Donald Trump called the federal government's $1.95 billion deal with Pfizer and biotech firm BioNTech "a historic agreement" that will help the country distribute a coronavirus vaccine in record-breaking time.

(With inputs from agency)

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