SAN FRANCISCO (KGO) -- It's the argument that some have used to not get vaccinated. "I've had COVID - therefore I don't need to get the vaccine."
Turns out that's not entirely true. On Friday, the Centers for Disease Control and Prevention released a study reporting that individuals who've had COVID are twice as likely to get reinfected.
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Luz Pena: "Is it dependent on the level of virus they were infected with?"
Dr. Timothy Henrich: "It seems to be and we don't know exactly how protected or how long the protection from natural infection will last," said Henrich UCSF Professor of Medicine in Residence.
Dr. Henrich has been studying the long term impacts of COVID-19 and says the immune response from natural infection is not as high.
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"Both antibody responses and cellular immune responses or for example T-cells that recognize SARS-CoV-2 infection can persist for months. Eight to 12 months after natural infection and most likely after vaccination. What we don't fully understand is how protected those immune responses are longer term overtime," said Dr. Henrich.
In the CDC study, residents who were infected with COVID in 2020 experienced a reinfection between May and June of 2021. That's the same time the Delta variant intensified across the country.
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"Hopefully this will push a number of people who've been holding out thinking they don't need a vaccine to go ahead and get vaccinated and get that protection," said Deepak Srivastava, President of Gladstone Institutes
The Delta variant accounts for more than 83 percent of virus across the U.S.
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Dr. Deepak Srivastava agrees with the CDC data but says reinfections among unvaccinated individuals could be higher than anticipated.
"I think that is very likely because we know the Delta variant is so much more infectious," said Dr. Srivastava.
The latest data shows the mRNA vaccines continue to be more than 90 percent effective in preventing hospitalization.