The United States expects to have four coronavirus candidate vaccines in large-scale clinical trials by the middle of September, a remarkable timeline considering the SARS-CoV-2 virus was only discovered in December.
The government is “very pleased” with the progress, Health and Human Services deputy chief of staff Paul Mango said Friday afternoon. Mango is the agency’s liaison with Operation Warp Speed, the White House-led task force on coronavirus vaccine and treatment development.
“We feel we are absolutely on track – if not a little bit ahead – in terms of our overall objective, which is tens of millions of (doses of) safe and effective vaccines approved for calendar year-end,” Mango said.
Each clinical trial will enroll 30,000 volunteers; the two underway are about halfway there, he said.
Early data on the vaccines show they cause volunteers’ bodies to produce significant amounts of neutralizing antibodies, Mango said. That doesn’t necessarily mean a vaccine candidate will protect against COVID-19, but it may.
At least at first, there will be a limited number of vaccine doses to distribute, said Robert Redfield, director of the Centers for Disease Control and Prevention. Certain groups of people will be targeted for vaccination first, such as the elderly or health care workers.
“We want to be prepared for whichever vaccine makes it through the gate,” Redfield said, to get it to whichever groups have priority.
Companies are manufacturing three of the six candidate vaccines Operation Warp Speed funded.
“For the other three, we are retrofitting a number of facilities – we are receiving equipment from all over the world – and those will start shortly as well,” Redfield said.
The government is planning how it will distribute whichever vaccines are approved, a complex logistical task, Mango said.
Five of the six vaccines require two doses, some spaced 21 days apart and some spaced 28 days apart. One must be stored at -94 degrees Fahrenheit, he said.
The United States has stockpiled hundreds of millions of needles, syringes and stoppers and ordered hundreds of millions more, Redfield said.
Decisions possible before studies complete
No doses of candidate vaccines can be distributed until the Food and Drug Administration declares them safe and effective. The first such approval could come as early as October, Mango said, though December is more likely, depending on how quickly clinical trials can be completed.
Only 150 to 175 people among the 30,000 in a clinical trial have to be infected with COVID-19 to test whether a candidate vaccine is effective, Redfield said.
At that point, scientists can “start looking at the data to determine if there’s significance or not,” Redfield said.
They would analyze how many of the infections were among volunteers who received the placebo rather than the vaccine to know whether it provided immunity.
A Data Safety Monitoring Board, independent of the government and the companies, determines at what point enough data has been collected to judge whether a vaccine is effective.
“They could come back before we’ve even had 30,000 folks enrolled and say, ‘We’ve seen enough, this looks great. Pass it on to the FDA,’ ” Mango said.
Some public health experts are worried the government will stop a trial early, once effectiveness is shown but before all 30,000 volunteers get two doses of a vaccine or placebo.
The board could extend a trial if not enough data is available after 30,000 patients receive either the vaccine or a placebo, Mango said. That could happen if not enough participants become infected with COVID-19 to detect effectiveness.
A trial could be halted if the data showed early on that a candidate was unsafe or ineffective, Redfield said.
Government could fund research into more vaccines
The United States supports eight vaccine candidates, but Mango said it could invest in more. Any new ones would have to be different from those already funded, he said.
“I would say we have become a little bit more discerning at this point,” he said.
Additional large-scale federal funding would probably go to a vaccine that could be delivered in one dose or orally rather than via injection.
Mango cautioned no outcome is certain.
“There are no guarantees in science,” Mango said, “but what Operation Warp Speed does is maximize the probability of having at least one acceptable vaccine in large quantities before the end of the year.”