Final results from Pfizer Inc's Covid-19 vaccine trial showed its shot had a 95 percent success rate and two months of safety data, paving the way for the drugmaker to apply for an emergency US authorisation within days, it said on Wednesday.
The vaccine's efficacy rate, the highest of any candidate in late-stage clinical trials so far, was welcomed by experts who had already said that interim results showing Pfizer's shot was over 90 percent effective were very encouraging.
Pfizer said there were 170 cases of Covid-19 in its trial of more than 43,000 volunteers and only eight people with the disease had been given the shot rather than a placebo, meaning the vaccine had a 95 percent efficacy rate. Of the 10 people who developed severe Covid-19, one had received the vaccine.
"The data is very strong," Britain's University of Reading professor of virology Ian Jones said.
"It's looking like a real contender."
Pfizer said it expected the US Food and Drug Administration's (FDA) vaccine advisory committee to review and discuss the data in a public meeting that will likely be held in December.
"We continue to move at the speed of science, and we know that every day matters in our path to authorisation," Pfizer chief executive Albert Bourla said.
The final analysis comes just a week after initial results from the trial showed the vaccine, developed with German partner BioNTech SE, was more than 90 percent effective.
Moderna Inc on Monday released preliminary data for its vaccine, showing 94.5 percent effectiveness.
The better-than-expected results from the two vaccines, both developed with new messenger RNA (mRNA) technology, have raised hopes for an end to a pandemic that has killed more than 1.3 million people and wreaked havoc upon economies and daily life.
However, while some groups such as healthcare workers will be prioritised in the US for vaccinations this year, it will be months before large-scale rollouts begin.
The most vulnerable
Distribution of a Pfizer shot is complicated by the need to store it at ultra-cold temperatures of -70C. It can, however, be kept in a normal fridge for up to five days, or up to 15 days in a thermal shipping box.
Pfizer said the efficacy of the vaccine was consistent across different age and ethnic groups, a sign that the immunisation could be employed broadly around the world.
Efficacy in adults over 65 years, who are at particular risk from the virus, was more than 94 percent.
"The 94 percent protection for older people is key. This is the evidence we needed to ensure that the most vulnerable people are protected," University of Liverpool department of pharmacology senior visiting research fellow Andrew Hill said.
Equity markets strengthened slightly on the Pfizer news.
Europe's STOXX 600 and the US S&P 500 futures both rose about 0.3 percent to hit highs for the day. The moves were small, however, compared with the jump when Pfizer first announced the vaccine was more than 90 percent effective on 9 November.
Pfizer shares rose 3 percent in premarket trade while BioNTech's US-listed shares jumped 8 percent.
Mild side effects
Pfizer said its two-dose vaccine, BNT162b2, was well-tolerated and that side effects were mostly mild to moderate, and cleared up quickly.
The only severe adverse event that affected more than 2 percent of those vaccinated was fatigue, which affected 3.7 percent of recipients after the second dose. Older adults tended to report fewer and milder adverse events.
Moderna named five categories of severe side effects experienced by at least 2 percent of those who received its vaccine. It listed fatigue at a frequency of 9.7 percent, muscle pain at 8.9 percent, joint pain at 5.2 percent, headache at 4.5 percent, pain at 4.1 percent and redness around the injection site at 2 percent.
Pfizer's final results come as the virus is running rampant around the world, placing an enormous strain on healthcare systems with record numbers of new cases and hospitalisations.
The approach of winter in the northern hemisphere in tandem with the holiday season is expected to worsen case numbers as people spend more time indoors and have family gatherings.
"With hundreds of thousands of people around the globe infected every day, we urgently need to get a safe and effective vaccine to the world," Pfizer's Bourla said.
Pfizer and BioNTech also said they planned to submit the data to other regulatory agencies around the world and submit data from the study to a peer-reviewed scientific journal.
Pfizer reiterated that it expects to make as many as 50 million vaccine doses this year, enough to protect 25 million people, and then produce up to 1.3 billion doses in 2021.
Of the dozens of drugmakers and research groups racing to develop vaccines against Covid-19, the next data release will likely be from AstraZeneca Plc with the University of Oxford in November or December.
Johnson & Johnson says it is on track to deliver data this year.