What is vaccine breakthrough?

Every day in the U.S., the number of people being vaccinated against COVID-19 grows. Daily, on average, more than 2.4 million people are being vaccinated.

According to the U.S. Centers for Disease Control and Prevention (CDC), more than 40% of American adults 18 and older are fully vaccinated against COVID-19. As more people roll up their sleeves to help end the pandemic, the CDC continues to study vaccine effectiveness, to ensure COVID-19 vaccines are working as expected.

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One of the things under the CDC’s microscope is vaccine breakthrough. Douglas Kasper, MD, the section head of infectious disease at the University of Illinois College of Medicine Peoria and a leader in the OSF HealthCare response to COVID-19, defines “vaccine breakthrough” as someone contracting COVID-19 and needing medical care, despite receiving the full course of the vaccine.

When is it considered vaccine breakthrough?

For a case to be considered vaccine breakthrough, the timing between vaccination and infection is the key.

“What’s important here is that a sufficient amount of time has passed from when they received the vaccine,” Dr. Kasper said. “So if somebody receives the vaccine on a Monday and contracts COVID-19 the following day, that does not count as a vaccine breakthrough. There has not been sufficient time for the body to create the protective immune response that we know will occur as usually two to four weeks pass after receiving the vaccine.”

While the CDC is investigating thousands of reported vaccine breakthrough cases, it is still a very small percentage of those who have received the full dose.

Vaccine breakthrough is expected

Breakthrough cases are expected for any vaccine, Dr. Kasper said. That’s because each person is unique and will respond to the virus and the vaccine differently.

“Any immune response is not uniform. How all of us interact with a virus will be different,” he said. “So because of that, vaccines or natural immunity are not 100% protective. We strive for 100%, but what we understand is that some number of people, even when they receive the vaccine, may become ill with the virus.

“What we know is that people who receive the vaccine, even if they become ill, tend to have more mild cases of disease than those who have not received the vaccine,” he said.

Breakthrough cases not a reason to avoid vaccination

For Dr. Kasper, the existence of COVID-19 vaccine breakthrough cases is not a reason for anyone to avoid the vaccine. The opposite, he said, is true. Continuing research shows the benefits of getting vaccinated far outweigh the risk of infection.

“Vaccine effectiveness remains well above 90% in real world reporting about adverse effects, which allows us to continue to safely deliver vaccine products to those within our community,” he said.

Get vaccinated

Currently, anyone 16 and older is eligible to receive the COVID-19 vaccine, and can now sign up for an appointment.

Dr. Kasper urges everyone, whether or not they’re vaccinated, to continue following public health guidelines to slow the spread of COVID-19.

About Author: Lisa Coon

Lisa Coon is a Writing Coordinator for OSF HealthCare, where she has worked since August 2016.  A Peoria native, she is a graduate of Bradley University with a degree in journalism. Previously, she worked as a reporter and editor at several newspapers in Iowa and Illinois.

She lives in Groveland with her husband and son. In her free time she likes to cook, bake and read. She freely admits that reality TV is a weakness, and she lives by the quote, “The beach is good for the soul.”

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Categories: COVID-19