As the race for a COVID-19 vaccine heads into the stretch run, scientists are tempering their enthusiasm with caution.

The biotechnology company Moderna and the National Institutes of Health have begun Phase III efficacy trials for their vaccine. The University of Oxford and Pfizer are running combined Phase II and III testing for their respective drugs. All together, drugmakers have 27 vaccines in trials.

The goal of Operation Warp Speed, the U.S. vaccine initiative, is 300 million doses of a safe, effective vaccine by January, and if realized, it would be one of the greatest scientific achievements of all time. On Tuesday, Goldman Sachs predicted the Food and Drug Administration would approve at least one vaccine before the end of the year.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said last month he was hopeful a vaccine would be available by late fall or early winter.

Here’s what worries scientists:

—FDA regulators will likely face enormous political pressure to approve a vaccine, even one that’s not proven safe and effective.

—A vaccine that’s less effective than billed could cause wider spread of the pandemic, Michael S. Kinch, director of the Centers for Research Innovation in Biotechnology and Drug Discovery at Washington University in St. Louis, writes in Stat News.

“A merely short-term effect could encourage vaccinated individuals to resume risky behaviors, which would all but guarantee that the epidemic endures,” argues Kinch, who is also a professor of biochemistry and molecular biophysics.

—A vaccine would likely erode compliance of social distancing and mask wearing, measures that are proven effective against spread of the virus.

“They automatically are going to say, ‘Oh great, I’m just going to get my little vaccine, and I can go back and do exactly the things I was doing last year’. That is absolutely not true,” Maria Elena Bottazzi, associate dean of the National School of Tropical Medicine at Baylor College of Medicine, told Business Insider in an interview.

—We don’t have enough data.

“What we have right now is a collection of animal data, immune response data and safety data based on early trials and from similar vaccines for other diseases,” writes Natalie Dean, assistant professor of biostatistics at the University of Florida, in the New York Times.

“The evidence that would convince me to get a COVID-19 vaccine, or to recommend that my loved ones get vaccinated, does not yet exist,” she says.

—If a substandard vaccine is green-lighted without adequate testing or trials, unforeseen harmful side effects could emerge. A weak initial vaccine and/or one with dangerous side effects would likely cause confidence in all vaccines to plummet and strengthen anti-vaccine sentiments. If a safer, more effective vaccine were subsequently developed, the residual mistrust could result in fewer people getting vaccinated.
 
—Epidemiologists estimate that to tame the pandemic, at least 70 percent of the population may need to develop immunity, either by vaccine or getting infected. Millions of Americans refusing to get inoculated by a vaccine that’s at least 50 percent effective (the minimum level according to the World Health Organization) could thwart that goal.

—A vaccine might only provide short-term immunity because of the nature of coronaviruses. Back in April, Dr. David States, professor of human genetics and director of bioinformatics at the University of Michigan, tweeted:

“If you’re hoping a vaccine is going to be a knight in shining armor saving the day, you may be in for a disappointment. SARS COV2 is a highly contagious virus. A vaccine will need to induce durable high level immunity, but coronaviruses often don’t induce that kind of immunity.”

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Mike Moffitt is an SFGATE Reporter. Email: moffitt@sfgate.com. Twitter: @Mike_at_SFGate





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