SARS-CoV-2 reinfection milder than primary infection in US study
SARS-CoV-2 reinfection was uncommon and milder than primary infection but was associated with two deaths, according to findings from a U.S. study published in Clinical Infectious Diseases.
“Reinfection remains a possibility in survivors of initial SARS-CoV-2 infection and should be considered if [the] clinical picture is consistent with SARS-CoV-2 infection,” Adnan I. Qureshi MD, professor of clinical neurology at the University of Missouri, told Healio.
“Therefore, policies regarding face masks, social distancing and vaccination apply to survivors of initial SARS-CoV-2 infection as well,” Qureshi said. “The results also indirectly suggest that vaccination may not provide complete immunity over a long period of time and periodic boosters may be necessary.”
Qureshi and colleagues analyzed data from 9,119 patients with SARS-CoV-2 in 62 U.S. health care facilities between Dec. 1, 2019, and Nov. 13, 2020. They analyzed the rate of reinfection — defined as two positive tests separated by more than 90 days after the resolution of the initial infection — associated factors, and mortality.
According to the results, reinfection occurred in 0.7% (95% CI, 0.15%-0.9%) of patients, with an average gap between positive tests of 116 ± 21 days. They found that asthma (OR = 1.9; 95% CI, 1.1-3.2) and nicotine dependence or tobacco use (OR = 2.7; 95% CI, 1.6-4.5) were associated with reinfection.
Two deaths were associated with reinfection, but significantly lower rates of heart failure, pneumonia and acute kidney injury occurred with reinfection compared with primary infection.
Qureshi said that the reinfection rate observed in this study is similar to rates observed in studies from the United Kingdom, Denmark and Qatar, but regional differences including immunization, COVID-19 protocols, the prevalence of variants and population density mean it is “very important to get data from each region.”
Qureshi also said that one of the study’s limitations was that reinfection was counted only if it occurred at least 90 days after primary infection, which may have resulted in earlier cases of reinfection not being accounted for.
“It remains unclear whether some individuals are immunodeficient or new variants of SARS-CoV-2 can evade immunity to a previous variant,” Qureshi said. “Furthermore, the immunity after the first SARS-CoV-2 infection may decline very quickly, unlike other viral infections.”