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November 17, 2020

How will the public know if a COVID-19 vaccine is truly safe and effective?

The FDA has pledged to make all emergency use authorization data available to the public. Here's the information scientists say is important to understand

Prevention COVID-19
COVID-19 vaccine safety Pavlo Gonchar/SOPA Images/Sipa USA

The FDA has increased transparency in the emergency use authorization process in hopes of building Americans' confidence in the safety and effectiveness of a COVID-19 vaccine. Moderna and Pfizer each expect to apply for an EUA later this year.

The need for accelerated COVID-19 treatments and vaccines remains urgent as the coronavirus continues its rampage across the United States.

But how can the general public rest assured they are truly safe and effective?

Normally, the backing of scientific leadership would be enough to instill confidence in the general public, but politicization of the pandemic response and the lightening-speed of all the research has hurt public confidence.

Back in June, the U.S. Food and Drug Administration revoked the emergency use authorization that allowed chloroquine phosphate and hydroxychloroquine sulfate donated to the Strategic National Stockpile to be used to treat certain hospitalized patients with COVID-19.

Early on in the pandemic, the antimalarial drug was hyped as a potential therapy for hospitalized coronavirus patients, but further research cast doubt on its safety and effectiveness, and the EUA eventually was revoked.

Confidence in COVID-19 vaccines is particularly low, according to STAT.  In a recent survey by ClearPath Strategies, only 38% of the participants said they would be willing to take a vaccine within the first few months after it was authorized. Another 33% said they would be willing to take it after three months while 29% said they would extend the waiting game for at least a year.

Other national surveys have reported a similar trend of low confidence.

So while Moderna is now the second U.S. drugmaker to announce that its COVID-19 vaccine candidate appears to have surpassed expectations for effectiveness, many Americans still seem wary of taking the vaccine when it eventually becomes available to the public.

In an effort to instill more confidence in the emergency use authorization process meant to accelerate the distribution of vaccines and therapies to the public, the FDA said Tuesday that the public will now have access to all COVID-19 data.

"Our drug and biological product centers intend, to the extent appropriate and permitted by law, to publicly post their reviews of the scientific data and information supporting the issuance, revision or revocation of EUAs for all drug and biological products, including vaccines, as part of our COVID-19 response," FDA Commissioner Dr. Stephen M. Hahn said.

He reiterated that the emergency use authorization is different from the approval process for drugs and biologics, including vaccines.

"Under the EUA process, in emergency situations when there are no adequate, approved and available alternatives, the FDA has the authority to authorize medical products for use under specified conditions before all the evidence that would be needed for full FDA approval is available," Hahn said.

While data transparency is important, interpreting the data can be a challenge – unless you're a scientist. Here's the key data points that scientific experts say you should be looking at: 

Overall effectiveness rate

The overall effectiveness rate is an important number. To calculate this number, the researchers compare the numbers of participants who have taken the vaccine who test positive or get sick to the number of participants who have taken the placebo who test positive or get sick.

If the vaccine is effective, the number of participants who receive the vaccine and get COVID-19 will be significantly lower than the number of participants who receive the placebo get COVID-19, according to Duke Health.

To submit for an emergency use authorization, vaccine makers must show at least a 50% efficacy. Early results from Pfizer's clinical trial indicate its vaccine has a 90% effectiveness rate. Moderna's has a 94.5% rate.

So if these results are confirmed in further study, it means these two vaccines will be highly protective against the virus.

In comparison, influenza vaccines are generally 40% to 60% effective while two doses of the measles vaccine are 97% effective, the New York Times reports.

Size and diversity of trial 

Though the public truly won't know how well a vaccine works until it administered in the real world, clinical trials with more volunteers enrolled provide a better sense of safety and effectiveness than smaller studies, experts say.

Having enough diversity among the participants also is necessary to ensure that the vaccine is safe to administer to all populations. 

The Pfizer vaccine trial has enrolled more than 45,000 participants, according to preliminary information released by the company. About 42% of global participants and 30% of U.S. participants have racially and ethnically diverse backgrounds.

The Moderna vaccine trial has enrolled more than 30,000 volunteers – 37% are racial and ethnic minorities.

Understanding safety data

Both adverse events and side effects are tracked in drug and vaccine trials, according to the Centers for Disease Control and Prevention.

An adverse event is any health issue that develops after the vaccine or therapy is administered. It may be caused by the intervention, but it also may be just a coincidence.

Side effects are health issues that can be directly traced to the intervention. Pain and soreness at the injection site is a common side effect for vaccines. So is a low-grade fever that goes in away in a few days.

The side effects of the different COVID-19 vaccine candidates appear to be a little more unpleasant than other vaccines, potentially interfering in the ability to conduct normal daily activities temporarily.

Public health experts, however, say that some mild to moderate side effects with a COVID-19 vaccine are to be expected.

It is a risk vs. benefit analysis when deciding on the overall safety and effectiveness of any drug, Hahn said. And even after emergency use authorizations are granted, the FDA continues to monitory the safety and effectiveness of all vaccines and therapies.

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