Study Suggests Covid-19 Reinfections Have Similar Severity as Original Infection

Colorized scanning electron micrograph of a cell (red) infected with SARS-CoV-2 virus particles (blue), isolated from a patient sample

Photo:  NIAID

Using health data from almost 213,000 Americans who experienced Covid-19 reinfections, researchers have found that severe infections from SARS-CoV-2—the virus that causes Covid-19—tend to foreshadow similar severity of infection the next time a person contracts the virus. Additionally, scientists discovered that Long Covid was more likely to occur after a first infection compared to a reinfection.

The study, funded by NIH’s Researching Covid to Enhance Recovery (RECOVER) Initiative, is published in Communications Medicine.

The analysis utilized data from the National Covid Cohort Collaborative (N3C). Researchers focused on individuals originally infected between March 2020 and Dec. 2022, and experienced a second infection by March 2023. Covid-19 vaccines, though not available during the entire study period, correlated with a protective effect.

About 27% of those with severe cases, defined as receiving hospital care for a coronavirus infection, also received hospital care for a reinfection. Adults with severe cases were more likely to have underlying health conditions and be ages 60 or older. In contrast, about 87% of those who had mild Covid cases the first time also had mild cases of reinfections.

Covid reinfections occurred at least two months after a first infection. They were most frequent when omicron variants were circulating in late 2021 and early 2022. Waning immunity and increased exposure to the coronavirus, including the highly infectious variants, likely accounted for the uptick.

Scientists also discovered that regardless of the variant, Long Covid—defined as experiencing long-term Covid-19 symptoms such as tiredness, coughing or having difficulty sleeping, breathing or thinking after an acute coronavirus infection—was more likely to occur after a first infection compared to a reinfection. 

Researchers also found that lower levels of albumin, a protein made by the liver, may indicate a higher risk for reinfection. This finding could indicate lower albumin as a possible risk marker for reinfection.

The study is supported by NIH’s RECOVER Initiative and NCATS.