FDA head Stephen Hahn said his agency won't be pressured into approving a vaccine

To gain approval, a vaccine will need to fully protect or lessen the severity of the disease in half of those who get it

140 vaccines are being tested

Dr. Anthony Fauci, the nation’s top infectious disease expert, told a House panel Tuesday despite intensive research and clinical testing, there’s no guarantee there will be a “safe and effective vaccine” against coronavirus, and failure to follow mitigation guidelines could see the daily case count rise to 100,000.

Dr. Robert Redfield, head of the Centers for Disease Control and Prevention, said at the same hearing efforts to conduct contact tracing is hurt by outdated public health data systems desperately in need of modernization.

Fauci, head of the National Institute of Allergies and Infectious Diseases, told the Senate Health, Education Labor and Pensions Committee, however, he still is optimistic an effective vaccine and treatments will be developed.

“There is no guarantee and anyone that's been involved in vaccinology will tell you that we will have a safe and effective vaccine, but we are optimistic that we will at least know the extent of efficacy sometime in the winter and early part of next year,” he said.

The administration is hoping to have 300 million doses of a vaccine by early next year. Currently, more than 140 are being tested.

Food and Drug Administration Commissioner Stephen Hahn told the panel the agency will require any vaccine to prevent disease or lessen severity in at least half of those who receive it. He said despite the urgency to find and approve a vaccine, the agency will not be pressured.

“We have an obligation to use all of our scientific knowledge, regulatory framework to ensure that any vaccine that comes before us, whether for authorization or approval, meets our stringent standards for safety and effectiveness,” he told lawmakers.

Fauci warned the nation could see the infection rate more than double to 100,000 cases a day if mitigation guidelines are not followed.

“We are now having 40-plus-thousand new cases a day,” Fauci said. “I would not be surprised if we go up to 100,000 a day if this does not turn around. And so I am very concerned.”

Fauci said Americans can still enjoy themselves within reason if they follow mitigation guidelines.

“Outdoors is always better than indoors,” Fauci testified, adding people should not look as public health endeavors to keep the virus from spreading as impediments. “Don’t just make it all or none.”

In recent days, new cases have been surging in states that attempted to reopen their economies rapidly, forcing some governors to roll back efforts.

Fauci said Europe has been more successful in stemming the spread of the virus because it took more stringent actions than those implemented in the U.S. He noted whereas U.S. compliance with stay-at-home strategies totaled about 50%, compliance in Europe was at 95%.

Sen. Mitt Romney, R-Utah, said Americans need data on where people are contracting the virus. Only then, he said, will people feel confident about returning to some semblance of normal.

Both he and Redfield testified 70% to 85% of the population will need to recover from the virus or get vaccinated for there to be any hope of herd immunity. Redfield estimated that so far, just 5% to 8% of the population has been exposed. Fauci cautioned researchers still don’t know whether recovery from virus will confer any kind of immunity or how long it will last.

By early afternoon Tuesday, more than 2.6 million coronavirus infections have been confirmed along with 126,360 deaths.

Redfield predicted a “difficult” fall and winter, saying Americans must be convinced to get flu vaccines. Currently, less than half of adults are vaccinated every year.

On a separate issue, Fauci addressed the new virus identified in China that has the potential for developing into a new pandemic. He said the virus, which shows characteristics of the H1N1 swine flu and the 1918 Spanish flu, currently poses no immediate no immediate threat, “but it’s something we need to keep our eye on.”