A 20-year study on dozens of vaccines finds they are safer than 'almost any other modern medical intervention'

A 20-year study on dozens of vaccines finds they are safer than 'almost any other modern medical intervention'
A patient receives a shot in the first-stage safety study clinical trial of a potential vaccine for COVID-19.Associated Press
  • A comprehensive new study spanning 20 years and including 57 vaccines found they're "remarkably safe," especially compared to pharmaceuticals and other medical devices.
  • The study found safety-related labeling changes were largely minor, such as to note people with allergies to the vaccine should steer clear.
  • The results may comfort those worried about a coronavirus vaccine that the people responsible for making sure vaccines are safe and effective are competent.

A comprehensive new study spanning 20 years and 57 vaccines finds vaccines are "remarkably safe" — safer, in fact, than "almost any other modern medical intervention," lead author Dr. Daniel Shepshelovich told Business Insider.

For the study, he and other researchers at Tel Aviv Sourasky Medical Center looked at the labels, including safety-related changes, of 57 vaccines that became FDA-approved between the beginning of 1996 and end of 2015.

They found there have been 58 label modifications among 25 vaccines due to minor safety issues. The most common reasons a label was updated, for example, were to indicate it shouldn't be used in certain populations (like pre-term infants) or to note people with an allergy to the vaccine should steer clear.

Only one vaccine was withdrawn for potential safety issues nine months after its approval.

The results demonstrate "the quality and thoroughness" of the FDA-approval and post-marketing surveillance processes, Shepshelovich said.


When similarly studying prescription drugs and medical devices, he and colleagues "came to expect an efficacy vs. risk tradeoff: a drug can help people and save lives, but at a cost of potential side effects," Shepshelovich said. "With vaccines, almost no significant side effects were identified, which I think is remarkable."

The study also showed how effective the FDA's Vaccine Adverse Event Reporting System is

Most of the studied vaccines, all against infectious diseases, were approved after being shown safe and effective in randomized controlled trials, the "gold standard" of research methods. The median number of participants in those trials was 4,161, making them fairly large, boosting their credibility.

The research team also looked at hundreds of thousands of reports from the FDA's Vaccine Adverse Event Reporting System (VAERS), a database of negative responses following vaccines, to see how well vaccines are continuously monitored even after they're shown to be safe and effective.

Of the 58 label modifications tracked over the 20-year-period, 95% were to include additional safety information, like to warn patients it's possible to faint after getting a shot.

Only one vaccine (a 1998 rotavirus vaccine) was withdrawn due to a rare (affecting somewhere between 1 in 5,000 to 1 in 10,000 infants) but potentially dangerous effect. The VAERS system helped flag it and have it removed from the market within a year.


Because the surveillance system is what tended to prompt the updated labels too, the researchers say their study shows it works, and works very well.

A 20-year study on dozens of vaccines finds they are safer than 'almost any other modern medical intervention'
Crystal Cox/Business Insider

Jennifer Reich, a University of Colorado Denver sociology professor who studies vaccine-hesitant parents, told Business Insider VAERS is among several "rigorous" systems that monitor vaccines' safety and efficacy.

"Some allow for voluntary reporting and others electronic health record and billing data to examine more subtle things, like an increase in emergency room or doctor visits after vaccination that could signal a pattern or adverse reaction," she said.

"It is a shame that so few people know about these systems and understand how well vaccine safety continues to be monitored long after a vaccine is licensed."


Americans are increasingly vaccine-hesitant

Vaccine hesitancy has been on the rise in the US in recent years.

That's tragic, Shepshelovich said, because "vaccines are one of the greatest achievements of modern public health, saving countless lives and all but eliminating once prevalent diseases such as mumps, measles, and poliomyelitis."

"The current COVID-19 pandemic is a frightening reminder of life with contagious infectious diseases without an effective vaccine," he added.

But rather than drawing more to the pro-vaccine camp, the pandemic has turned up even more skeptics. A May poll, for one, found that only about half of Americans would get a coronavirus vaccine, should one become available, while 31% were unsure.

Shepshelovich said he doesn't expect his study, which included all pre-coronavirus data, to change all vaccine skeptics' minds. But he hopes it may influence some who are looking to legitimate evidence to develop their stance.


"I would tell vaccine-hesitant people that the science and the evidence are clearer on vaccine safety than on almost any other modern medical intervention. The benefits are huge. And the risk is very very small," Shepshelovich said.

He also said his study underscores the competence of teams responsible for making sure vaccines are safe and effective before making it to market and beyond.

"We showed that the people in charge of approving, regulating, and following vaccines have proved that they can be trusted with this responsibility," Shepshelovich said. "They have done this many times before."