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The american president Donald trump he has repeatedly said a vaccine is possible before the Nov. 3 election, and accused a “deep state” within the nation’s top health regulator of trying to delay critical clinical trials to hamper his chances for a second term.
The US Food and Drug Administration denied that claim, saying its decisions will be based on data alone. Drug makers, seeking to bolster public confidence amid political disputes, pledged Tuesday to uphold scientific standards for safety and efficacy in their search for a vaccine.
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Vaccine safety focused on Wednesday after AstraZeneca PLC said it had put its coronavirus vaccine trial on hold with Oxford to review safety data for an unexplained disease in the UK trial. She described the measure as routine and said she would restart trials when an independent committee recommended it.
Other companies have recently made comments suggesting that they might have an answer on whether their vaccines work before November.
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“It would really be an amazing vaccine to demonstrate that,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told Reuters.
Fauci said the results of the initial trial are likely to be available in November or December, but that late October remains a possibility. “It’s conceivable that if there are enough documented infections early on, you could get that answer sooner,” he said.
Vaccines must show that they are at least 50% more effective than a placebo to be considered for approval. To prove that, government officials have said, at least 150 Covid-19 infections must be recorded among trial participants and at least twice as many as occur in the placebo group.
If a vaccine is especially effective, companies might have their answer sooner. Pfizer Inc and Moderna Inc, whose US vaccine trials have enrolled thousands of people and are the most advanced, say they may have tests after only a few dozen subjects become infected.
Independent panels of experts called security and data monitoring boards (DSMB) will review the test data at pre-set points. These boards can recommend that companies stop lawsuits if the evidence is overwhelmingly positive or negative.
For Pfizer, the first tentative look occurs when 32 trial volunteers become infected.
Experts interviewed by Reuters warned that information obtained from a limited number of subjects could miss important security concerns that could reveal if the test is allowed to run fully.
‘Absolutely insufficient’
Pfizer’s test requires four interim tests by the DSMB, the first after only 32 recorded infections. “We may have enough data to be able to share the first analysis in October,” said Pfizer spokeswoman Jerica Pitts.
Moderna’s first interim analysis will come after 53 test subjects become infected, the company told investors last month.
Basing a decision on 53 cases is “an absolutely insufficient number,” said Dr. Gregory Poland, a vaccine researcher at the Mayo Clinic in Rochester who has served on the FDA’s vaccine advisory panels. “You would know very little about security.”
To stop trials due to positive results, vaccines will likely have to exceed the 50% efficacy threshold.
Pfizer has not disclosed which standard will be used to stop its testing early. William Gruber, Pfizer’s head of vaccine research and clinical development, said “the standard would be evidence of very high efficacy.”
A senior official in the US effort to accelerate the development of the Covid-19 vaccine said that companies have created appropriate trials to conduct interim tests that could detect especially effective vaccines earlier.
Quick enrollment
Although both drug makers began vaccinating people in their respective 30,000-subject trials on July 28, Pfizer is in a position to generate results earlier, in part because it is administering the second injection of its two-dose vaccine a week earlier than Modern Moderna also slowed enrollment to ensure greater participation by at-risk minorities in its study.
The Pfizer test also begins collecting data on infections that occur one week after giving your second injection. Moderna has a two week delay between the second injection and when it will start collecting serious infection data.
Both trials are on track to be fully enrolled soon.
Dr. Henry Miller, principal investigator of the Pacific Research Institute think tank and former director of the FDA’s office of biotechnology, said that an emergency use authorization based on a small number of infections would not provide an adequate answer on the safety of a vaccine intended for use by millions of healthy people. Some side effects could take four to six months to occur, he said.
Dr. Gregory Glenn, Head of Research at Novavax Inc, which is also developing a coronavirus vaccine, said the October schedule is still possible. But he thinks Americans will likely wait longer.
“I think humility is a good thing right now,” he said. “The FDA set some pretty strict criteria for success. So it will take a pretty good vaccine to do that.”
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