The Journal Gazette
Wednesday, July 21, 2021 1:00 am

Vital context on vaccine risks

Justin Vesser

While COVID-19 vaccines have been proved to be safe and effective, recent reports of rare adverse events, or side effects, have raised concerns.

On July 12, the Food and Drug Administration approved an update to the Johnson & Johnson COVID-19 vaccine fact sheet to include an increased risk of the rare nerve condition Guillain-Barré syndrome. This follows previous reports linking the J&J vaccine with a rare blood clot.

While reports such as these can be scary, they're a sign that the vaccine safety reporting system is working. They also highlight how the relative risks of rare side effects such as these need to be put into context.

I've seen how uncertainty and fear can drive vaccine hesitancy. Understanding how information about adverse events is collected and what it means for vaccine safety may help people make informed decisions.

The FDA enforces rigorous testing and approval processes that manufacturers must follow before a new vaccine can be made available.

Regardless of whether a vaccine is approved through the typical FDA approval process or an Emergency Use Authorization, the steps required to test a new drug for safety and effectiveness are the same. An Emergency Use Authorization can get a vaccine to the public more quickly by streamlining the regulatory process, but no shortcuts are taken

Vaccine clinical trials occur in four sequential phases. In the first three, study investigators identify, quantify and document safety issues. Phase 1 typically introduces the vaccine to fewer than 100 people over several months under controlled conditions. Typically, the majority of potential adverse events are identified in this stage.

After the FDA reviews Phase 1 data and deems the vaccine safe enough to be studied further, the vaccine moves on to Phases 2 and 3, where it will be given to larger numbers of people over longer periods of time. Here, investigators determine optimal dosage and screen for rare side effects.

If Phase 2 and 3 data meets FDA approval standards, the vaccine will move on to Phase 4 and become available to the public. The vaccine is observed over much larger populations and extended periods of time, and manufacturers are required to regularly check and report potential safety concerns to the FDA.

What's different about this final phase is that the public can also contribute to safety reporting. The Vaccine Adverse Event Reporting System is a national safety monitoring system. Anyone can submit a report. Recent adverse events associated with the COVID-19 vaccine were identified through the reporting system.

A rare adverse event may take months or years to identify for a simple reason: It's rare. For some drugs that are less commonly used, new safety data takes longer to discover because a relatively small number of patients use the drug. 

For cases like the COVID-19 vaccine, however, millions of people will receive the drug shortly after it's released to the public, and new issues or patterns often emerge more quickly.

Adverse events that occur closely following vaccination may not be caused by or even related to the vaccine.

This can lead to two problems.

First, not every reported adverse event is directly related to the vaccine. Correlation does not imply causation.

Second, a plausibly identified adverse event does not necessarily make the vaccine unsafe. Administering one vaccine to a huge sample of people can make it easier to identify a possible connection between the shot and a side effect. But that doesn't mean the risk of getting that side effect is very likely, or that it outweighs the benefit of getting vaccinated.

These risks, while real and potentially life-threatening, must be viewed in context with the much larger risk of negative outcomes from the diseases vaccines protect people from.

In such extraordinary times as during a pandemic, it's understandable people may be hesitant to take on any more risk than they have to. But there are safety nets in place to monitor the COVID-19 vaccines, and they are still working as they should.

The vaccines are proven to be overwhelmingly safe. More than 40,000 patients participated in J&J's clinical trials before the company applied for emergency use authorization, mirroring Pfizer's and Moderna's study sample sizes. Some 0.4% of participants in the J&J trial experienced serious adverse events unrelated to COVID-19 infection. In contrast, the trial demonstrated that people who get the vaccine are 85% less likely to get severe COVID-19 than those who remain unvaccinated.

The extremely rare side effects were discovered because safety reporting tools were used appropriately. Being aware of the risks of a treatment, however rare, can help people make health decisions that work best for them. However, these risks must be viewed in context. And in the case of the COVID-19 vaccines, they must be weighed against the consequences of remaining unvaccinated and letting the pandemic rage on.

Justin Vesser is manager of ambulatory pharmacy services for the University of Virginia.

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