In a major boost to vaccine development, Pfizer and its collaborator BioNTech released early study results Monday indicating that their vaccine, BNT162b2, prevented more than 90% of infections with the virus that causes COVID-19.

In the newly released data on the first 94 trial participants to come down with COVID-19, the vaccine was found to be more than 90% effective in preventing the disease. Half the participants received a placebo and half the vaccine, so the new data shows that more people who received the placebo than the vaccine came down with COVID-19.

They were protected a week after the second dose of the vaccine. The two doses are given 21 days apart.

There were no serious safety concerns reported to the independent data monitoring board that reviews both safety and effectiveness data. The board, which had the power to stop the trial if the vaccine was ineffective, recommended that the trial continue, as planned.

As the large Phase 3 study continues, the level of effectiveness may vary.

Pfizer and the German biotechnology company BioNTech, which developed the candidate vaccine, have enrolled more than 43,000 volunteers, nearly 39,000 of whom have received both doses of the candidate vaccine. They recently expanded their trial to include teens and children as young as 12.

Approximately 30% of the American trial participants have racially and ethnically diverse backgrounds, according to the companies.

Pfizer and BioNTech had been expected to release results several weeks ago, after 32 of the trial participants came down with COVID-19, but decided after discussion with the U.S. Food and Drug Administration to wait until more participants fell ill.

“Today is a great day for science and humanity,” said Dr. Albert Bourla, Pfizer Chairman and CEO in a prepared statement. “We are reaching this critical milestone in our vaccine development program at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen. With today’s news, we are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis.”

By the third week in November, Bourla said the companies should have enough safety and effectiveness data to submit a request for emergency approval to the FDA. Monday’s statement said the companies are “working to prepare the necessary safety and manufacturing data to submit to the FDA.”

The companies will monitor participants for long-term protection and safety for an additional two years after their second dose. Most serious vaccine side effects show up within the first six weeks of vaccination, so the FDA has required companies making candidate vaccines to wait until at least half of trial participants were two months past their second shot, to ensure safety

Pfizer expects to produce up to 50 million doses of BNT162b2 this year and 1.3 billion next year.

Austin Regional Clinic's Clinical Research Division is enrolling 250 people in a Pfizer vaccine trial for the coronavirus.

Moderna, which is using the same mRNA vaccine technology as Pfizer/BioNTech, is likely to be the next federally funded vaccine developer to release interim effectiveness data. Its trial, which reached full enrollment last month, calls for 53 infections before the first interim analysis, which is expected to happen shortly.

Two other Phase 3 trials funded by the U.S. government, one from AstraZeneca/Oxford University and the other from Johnson & Johnson, restarted after delays caused by unexplained illnesses. The FDA decided last month those illnesses could not definitively be blamed on the vaccine, so they allowed those trials to resume.

AstraZeneca also has a large trial in the U.K., which was paused for less time than the U.S. one and so could report its first data soon.

Unfortunately for those infected, all the trials have been helped by the fact that COVID-19 continues to rage through the U.S. and several other countries where trials are being run. The worse the outbreak, the sooner enough trial participants will fall ill and determine each candidate vaccine’s effectiveness.

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