COVID-19 patients may maintain immunity to the virus for up to eight months after initial infection, according to two studies published Dec. 22.
For the first study, published in Science Immunology, Australian researchers took repeat blood samples from 25 COVID-19 patients from day four to day 242 after infection. Every patient had memory B cells up to eight months after infection, which are immune cells that trigger antibody production if re-exposed to the virus.
"These results are important because they show, definitively, that patients infected with the COVID-19 virus do in fact retain immunity against the virus and the disease," senior author Menno van Zelm, PhD, a researcher at Monash University's department of immunology and pathology in Melbourne, said in a news release.
The second study, published in Emerging Infectious Diseases, assessed antibody responses in 58 COVID-19 patients in South Korea who had asymptomatic or mild cases between March 5 and April 9. Researchers measured antibody levels using four commercial immunoassays. Results from three immunoassays showed antibody levels were still high eight months after infection.
"Rates differed according to immunoassay methods or manufacturers, thereby explaining differences in rates [from past studies]," the researchers said, which suggested antibody levels waned after two to three months.
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