In all likelihood, Americans will soon begin to receive vaccines that prevent COVID-19, a disease that has killed more than 230,000 people. Nonetheless, per an Oct. 19 STAT/Harris survey, about half of those polled will refuse a vaccine.

At some level, this reluctance is understandable. The language surrounding the vaccine effort—including phrases like “Warp Speed,” “the race for a vaccine,” and “vaccine finalists”—has caused concern that critical phases of development have been truncated or, worse, that safety guidelines have been ignored.

Further, many Americans have lost trust in federal oversight. Treatments for COVID-19, such as the anti-malarial drug, hydroxychloroquine, and convalescent plasma, donated by people who have survived this infection, were enthusiastically approved by the Food and Drug Administration (FDA), even though none had been shown to work and one, hydroxychloroquine, was dangerous. The lightning-quick mechanism by which these products were approved, called Emergency Use Authorization (EUA), is the same mechanism by which COVID-19 vaccines will be approved.

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Yet a world of difference separates COVID-19 drugs and vaccines. Unlike hydroxychloroquine and convalescent plasma, vaccines will be tested in large, placebo-controlled trials involving tens of thousands of participants prior to approval. These trials will allow researchers to determine whether vaccines work and are safe. For example, Moderna’s vaccine trial includes 30,000 participants, Pfizer’s 44,000, and Johnson & Johnson’s 60,000. The size of these studies is typical for vaccines submitted for licensure during the past 70 years. The human papillomavirus (HPV) vaccine, which prevents several different types of cancer, was studied in 30,000 people before licensure.

The logical question now is that if studies of COVID-19 vaccines are typical of other vaccine studies, why use the EUA mechanism for approval? Why don’t companies do what they’ve always done: submit a Biologics License Application to the FDA? The answer lies in the length of these studies. In all likelihood, COVID-19 vaccine phase 3 trials will be completed in 6 to 8 months. The FDA would never normally license a vaccine that had been tested for such a short period of time. The HPV vaccine was tested for seven years before licensure.

By testing COVID-19 vaccines for such a short period, are we taking an unnecessary risk?

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For several reasons, I think the answer to this question is “no.” First, and most importantly, how will we know that these vaccines are safe if participants have only been followed for a few months before approval? Vaccines, like any product with a positive effect, can have negative effects. Sometimes severely. The oral polio vaccine is a very rare cause of polio. The influenza vaccine is a rare cause of Guillain-Barré Syndrome, ascending paralysis that starts in the legs and works its way up the body. The yellow fever vaccine is a rare cause of a severe disease that looks like yellow fever. About 1 of every 1 million doses of vaccines is complicated by a severe allergic reaction.

These exceedingly rare problems all occur within about six weeks of receiving vaccines, and within about 30 minutes for severe allergic reaction. So the several-month follow-up of participants in COVID-19 trials is likely long enough to pick up rare, serious side effects. Plus, systems like the Vaccine Safety DataLink, monitoring tens of millions of Americans who either have or haven’t received COVID-19 vaccines, will be in place after these vaccines are released.

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What about vaccine effectiveness? If these vaccines have been shown to work for only a few months, how will we know that they will still be effective for a year or more? The short answer is we won’t know until later. But it’s likely that a vaccine that is effective for a few months will work for longer. Also, it’s unreasonable to expect that clinical trials of these vaccines should go on for years when COVID-19 has killed hundreds of thousands of people in the United States in less than one year.

In the end, although COVID-19 vaccines will likely be approved by the same EUA process that led to the release of unproven, arguably harmful treatments, the large clinical trials of vaccines should reduce a critical amount of uncertainty before approval.

Paul A. Offit, MD is a member of the FDA’s Vaccine Advisory Committee, Director of the Vaccine Education Center at the Children’s Hospital of Philadelphia, and Maurice R. Hilleman Professor of Pediatrics at the Perelman School of Medicine at the University of Pennsylvania.