How strong is the evidence that it is possible to get SARS‐CoV‐2 twice? A systematic review

Abstract

Summary With a large number of coronavirus disease 2019 (Covid‐19) patients being discharged from hospital with negative test results for SARS‐CoV‐2, it has been reported that several recovered cases tested positive after discharge (re‐positive, RP). This finding has raised several important questions for this novel coronavirus and Covid‐19 disease. In this review, we have discussed several important questions, including: (1) Can the virus re‐infect recovered individuals? (2) What are the possible causes of the re‐positive reverse transcriptase‐polymerase chain reaction (RT‐PCR) test in recovered patients? (3) What are the implications of these re‐positive cases concerning the spread of the virus? Understanding how recovery from Covid‐19 confers immunity to decrease the risk of re‐infection is needed to inform current efforts to safely scale back population‐based interventions, such as physical distancing. We have also described what is currently known about the immune response to Covid‐19, highlighted key gaps in knowledge, and identified opportunities for future research. Overall, the quality of the evidence is poor and we describe the features that should be described for future cases.

The prevalence of adaptive immunity to COVID-19 and reinfection after recovery – a comprehensive systematic review and meta-analysis

“…We found that the prevalence of reinfection after recovery from COVID-19 was very low and that prior infection with SARS-CoV-2 conferred an 80% protective efficacy against reinfection (assuming baseline prevalence of 5%). The existing reviews [23,[97][98][99][100][101][102][103][104][105][106] have not examined the question of prevalent immunity sufficiently (Supplementary Table 4).…”

The prevalence of adaptive immunity to COVID-19 and reinfection after recovery – a comprehensive systematic review and meta-analysis

“…In a letter to the editor published at the time of finalization of this review, the prevalence of reinfection in a period of up to 12 months was 0.3% in Italy (112). Findings from this Italian study (101) also suggested a strong protective efficacy of prior infection with a hazard ratio of 0.06 (95%CI 0.005 – 0.08). In the USA, another study of 9119 individuals (113) with serial tests at least 90 days apart, during December 2019 to November 2020, published at the time of finalization of this review, also showed a low prevalence of reinfection of 0.7% (95%CI 0.5-0.9) (89).…”

“…Findings from this Italian study (101) also suggested a strong protective efficacy of prior infection with a hazard ratio of 0.06 (95%CI 0.005 – 0.08). In the USA, another study of 9119 individuals (102) with serial tests at least 90 days apart, during December 2019 to November 2020, published at the time of finalization of this review, also showed a low prevalence of reinfection of 0.7% (95%CI 0.5-0.9) (89). More research is also needed to measure protective efficacy in the long term.…”

“…We found that the prevalence of reinfection after recovery from COVID-19 was very low and that prior infection with SARS-CoV-2 conferred an 80% protective efficacy against reinfection (assuming baseline prevalence of 5%). The existing reviews (23,(85)(86)(87)(88)(89)(90)(91)(92)(93)(94) have not examined the question of prevalent immunity sufficiently (Supplementary Table 4).…”

Confirmed reinfection with SARS‐CoV‐2 during a pregnancy: A case report

“…We are reporting a case of reinfection with SARS‐CoV‐2 during a pregnancy in a healthy, immunocompetent woman. The woman had mild symptoms in both episodes, but milder symptoms during the first episode, as reported in most, but not all, previous case reports on reinfection with SARS‐CoV‐2 13 . Unfortunately, the first serology test was not done earlier than 2 months after the first infection.…”