Timeline of the COVID-19 vaccine development

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Each year, millions of vaccines to prevent infectious diseases are given to infants, children, adolescents and adults — and it’s critical that they are safe and effective.

The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) work together through an established system to ensure vaccines distributed in the U.S. are as safe as possible. As always, safety was the top priority throughout the rapid development and reviews of the newest COVID-19 vaccines.

Following are key steps that were taken in their development, testing, review and authorization:

Vaccine developers had a head start — While the process used to create the COVID-19 vaccines is novel, it’s not an unfamiliar technology, says Clay Dunagan, MD, BJC HealthCare chief clinical officer and infectious disease specialist. In fact, scientists have been working on coronavirus vaccines for decades.

“This vaccine strategy was explored in the original SARS (severe acute respiratory syndrome) and MERS (Middle-East respiratory syndrome) virus outbreaks,” Dr. Dunagan says. “So, it’s not unprecedented for use in people.”

Neither of those viruses turned out to spread as quickly as SARS-CoV-2, the virus that causes COVID-19, however, so those vaccines were never brought to market at the time.

No short-cuts were taken — A typical timeline for developing a vaccine is about seven years, involving a series of linear steps, each one executed and completed before progressing to the next step, says Dr. Dunagan.

“But because of the critical importance of getting COVID-19 vaccines to market, our country’s medical infrastructure changed that timeline, executing and successfully completing all of the steps in parallel,” Dr. Dunagan says. “No steps were skipped. Instead, the developers were acting as if the previous step had been completed successfully — and in that way they were able to dramatically shorten the timeline.”

In doing so, Dr. Dunagan says, the vaccine manufacturers were able to compress a seven-year timeline into a year of intense development — without compromising any of the steps in any way.

Careful testing occurred — The FDA set rigorous standards for vaccine developers to meet.

According to Dr. Dunagan, during safety testing of the COVID-19 vaccines, some 74,000 people received one of the two vaccines that are now being distributed by Pfizer and Moderna. The vaccines were tested on individuals of different ages, genders, ethnicities and races.

From these early trials, very few problems arose, and there were no reports of any serious side effects. The most common reactions were the usual immediate effects from a vaccination, such as soreness at the injection site or feeling a little “under the weather.” (See “What about side effects?” below.)

The FDA and two independent advisory committees very carefully reviewed the data amassed during these clinical trials.

Authorization for emergency use granted — The FDA is required to make decisions that are guided by science and data regarding authorization or approval of vaccines.

In December, after a thorough review, the FDA granted Emergency Use Authorization (EUA) for both the Pfizer and Moderna COVID-19 vaccines, which were shown to be safe and effective based on the data from the manufacturers and the findings from large clinical trials.

The data demonstrated that the clear benefits of these vaccines in protecting against COVID-19 outweighed the risks of side effects from the vaccine.

With a 95% effectiveness rate, the Pfizer and Moderna vaccines are an important tool in stopping the pandemic, along with other precautions like masks and physical distancing, the CDC says.

Continuous monitoring for problems and side effects — Safety evaluation continues even after a vaccine is approved. The CDC and FDA monitor all U.S. vaccines for safety and provide data and insight continuously to government health agencies, public health partners and the general public.

This is true for the COVID-19 vaccines, and systems are in place to track problems or side effects that were not evident during the clinical trials. A small number of allergic reactions have been reported since the release of the vaccine.

To assist in this tracking, those who have received the vaccine can report any side effects using a mobile app called v-safeSM. The app uses text messaging to initiate web-based monitoring, and any significant event reported by a participant is sent to the Vaccine Adverse Event Reporting System (VAERS) for follow-up. BJC is also reporting any serious side effects to vaccine monitoring systems.

What about side effects?

Dr. Dunagan says both the Moderna and Pfizer vaccines can cause side effects that are similar to those associated with other vaccines:

  • injection site soreness

  • fever

  • muscle pain

  • fatigue

  • headache

The side effects typically last only a day or two. Among BJC employees, only about 1% of those vaccinated have reported some minor side effects. The CDC projects only 2% of those who receive the vaccine will have side effects significant enough to stop their usual daily activities.

If you have allergies, however, especially severe ones that require you to carry an EpiPen, discuss the COVID-19 vaccine with your doctor, who can assess your risk and provide more information on if and how you can get vaccinated safely.

If you have underlying medical conditions such as diabetes or heart disease, you are at higher risk for complications from COVID-19, so it is even more critical that you receive the vaccine. If you have concerns, consult with the doctor who is helping you manage your condition.

Learn more about vaccine side effects and advice for those with special health concerns.

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