A healthy living blog from Marshfield Clinic Health System

Why do I keep getting COVID-19?

As time continues to move forward since the COVID-19 pandemic began, stories about people getting COVID-19 for a second or even third time continue to come to light.

Some of these individuals were even vaccinated, which has caused some to doubt the effectiveness of COVID-19 vaccines.

Your body produces antibodies after you get COVID-19. Antibodies are the primary defense against future infection. However, COVID-19 variants complicate the situation.

While it may be natural to question the vaccines or COVID-19 in general, many scientists and doctors predicted individuals would have COVID-19 several times.

“Many infectious diseases evolve over time. Virus evolution can lead to new strains that spread more easily or escape the immune system,” said Dr. Edward Belongia, epidemiologist and COVID-19 researcher with Marshfield Clinic Research Institute. “COVID-19 is the latest example of such infectious diseases.”

Protection after COVID-19 infection

A COVID-19 infection triggers an immune response that reduces the risk of getting COVID-19 again for several months.

Your body produces antibodies after you get COVID-19. Antibodies are the primary defense against future infection. Antibodies decline over time, but immune system cells (T cells) provide long lasting protection against more severe COVID-19 illness.

“The strength and duration of natural immunity may vary greatly in different people,” Dr. Belongia said. “Antibody levels are generally lower after a mild case of COVID-19. Age and health status also affect the level of natural immunity and risk of reinfection.”

COVID-19 variants further complicate the situation. For example, natural immunity against the Omicron variant is reduced in people who were infected with earlier variants such as Delta.

Protection after COVID-19 vaccination

Research has shown that protection against COVID-19 infection declines over time after vaccination. This is why the Centers for Disease Control and Prevention (CDC) recommends a booster five months after completing the initial COVID-19 vaccine series.

Even so, research has shown vaccines maintain a high level of protection against severe COVID-19 over time.

There are also benefits to vaccination if someone previously had COVID-19. Vaccination after infection will boost antibody levels and reduce the risk of reinfection. This is because your COVID-19 antibody levels get a large boost after vaccination.

For more information about COVID-19 reinfections, talk with your doctor.

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