Fauci says he's 'cautiously optimistic' about Moderna COVID-19 vaccine

National Institute for Allergy and Infectious Diseases Director Anthony Fauci, M.D., said he's concerned that massive protests across the U.S. and the lack of social distancing measures at these protests could fuel a surge in coronavirus cases. (NIAID)

Infectious disease expert Anthony Fauci, M.D., says he's "cautiously optimistic" about biotech company Moderna's COVID-19 vaccine candidate.

But he believes a successful COVID-19 vaccine will not be a "one and done" and will require a booster dose to provide immunity.

"When you induce a response with a vaccine that would be protective, a big unknown is the durability of that protection. Is it going to be a year, two years, or unfortunately, six months or less?" said Fauci, director of the National Institute for Allergy and Infectious Diseases (NIAID), speaking during a Wall Street Journal health technology event Tuesday.

"If it's measured in several months instead of years, and that's entirely conceivable, then we have a secondary problem. We get into a logistics issue of how often we need to boost somebody to get immunity up," he said.

Unlike a measles infection, which can in most cases provide lifetime immunity, coronaviruses that can cause the common cold generally don't result in long-lasting immunity after infection, Fauci said.

"I am concerned that with a successful vaccine we may have to do boosting because of the durability of the response," he said.

Last month, Moderna announced promising preliminary data from the phase I study of mRNA-1273, its messenger RNA-based vaccine against the SARS-CoV-2 virus. The study is being run by NIAID.

Fauci said the messenger RNA-based platform to develop the vaccine is "quite promising." 

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"It's easy to scale up and relatively flexible technology. It's one of the several reasons we thought it was a good idea to pursue it. We’re optimistic that we will be successful with this. But it is not the only candidate we are pursuing," he said.

"There is enough good science and enough activity, interest, and effort going into a coronavirus vaccine that within a reasonable period of time we hopefully will have more than one successful candidate," Fauci said.

Moderna's vaccine is one of eight vaccines under development that have been approved for clinical trials, according to the World Health Organization. Half of those vaccines are being developed in China, where the outbreak first emerged, NPR reported.

Chinese and U.S. scientists could develop a successful coronavirus vaccine "at about the same time, plus or minus a month," Fauci said.

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The infectious disease expert also said he was concerned that massive protests across the U.S. over the death of George Floyd and the lack of social distancing measures at these protests could fuel a surge in coronavirus cases.

"Any congregation of crowds can clearly increase the risk of transmissibility. And actions associated with social disruption, people not wearing masks and interacting and struggling with each other, that increases the risk of infection," he said. "I am concerned that social disruptions in the form of rioting will have a negative impact that might lead to an uptick and a resurge of infections."

When it comes to a more orderly congregation of people, such as at the ballot box, Fauci said local and state officials should consider the dynamics in their regions when making decisions about whether to hold in-person elections.

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"Ths is a large country with a wide degree of variability and the dynamics of the outbreak. There's a big difference between New York City at height of the outbreak and Wyoming. If you look county by county, there are some counties with no infection," he said. "You need to gauge your decision about the acceptability of being near other people based on the outbreak. I think it's going to vary from place to place."

While there is no doubt the U.S. will see a return of coronavirus infections in the fall and winter, Fauci said it's "not inevitable" that there will be a second wave like the first wave that began in March.

"It depends on how effectively we’re able to respond to those inevitable blips that we’re going to see for sure, and how we respond to them having the manpower, the system, the structure, and the tests and the ability to do identification, isolation and contact tracing. That plays a major role in whether have a second wave," he said.