#15,916
We are (officially) a little more than 13 months into the COVID pandemic, and while we are starting to see some hopeful signs in some countries - in others, like India and Brazil - things are getting worse. New variants continue to emerge, some able to at least partially evade current vaccines, and COVID reinfections are increasingly being reported.
Whether the progress currently being made in the United States and a number of other countries can be sustained, remains unknown.
The future course of the pandemic would seem to hinge on 4 primary factors. The emergence and spread of `vaccine escape' variants, reinfection rates, vaccine uptake (and effectiveness), and the public's willingness to continue to social distance and take other NPIs (non-pharmaceutical interventions) when appropriate.
Up until a little over 4 months ago, COVID variants were viewed as more of a scientific curiosity than a threat. Many had been identified, but none had appeared to pose a significant threat over `classic COVID'. All of that changed in mid-December with the announcement of the B.1.1.7 variant in the UK, followed by a plethora of others (B.1.356, P.1, B.1.617, etc.).
Similarly, reinfection with the SARS-CoV-2 virus - at least for a year - was considered unlikely 12 months ago. Early reports were often dismissed as more likely to be `relapses', not reinfections (see Osaka Japan: `Recovered' Patient Tests Positive For COVID-19).
When laboratory confirmed reinfections were finally document in the late summer of 2020 (see HKU Med Announces 1st Documented Reinfection With SARS-CoV-2). the assumption was they were rare, and were most likely to be mild or asymptomatic.
Since then we've seen evidence that reinfections can run the gamut, from being mild or asymptomatic, to being severe or even fatal. And slowly, we've seen evidence that as more time passes, and the SARS-CoV-2 virus evolves, the number of documented reinfections - while still relatively small - continues to rise.
Right now, we don't have a good handle on how common reinfections are, or are likely to become. Two weeks ago, in order to better quantify the threat, we looked at the ECDC's attempt to standardize case definitions and reporting (see ECDC Technical Rpt: Reinfection with SARS-CoV-2 (Surveillance Case Definition).
Just over a month ago, in Denmark SSI: Assessment of Protection Against Reinfection with SARS-CoV-2, the Statens Serum Institut published their report on 4 million Danes who received multiple PCR tests in 2020. From that researchers calculated the average person is about 80% protected - at in the short term - against reinfection with COVID-19.
Among those aged 65 and over, however, that protection was estimated to be only 47%.
This protection was assumed to last at least 6 months. Of note, these results were based on the older, `wild type' COVID, not the more recently emerged variants carrying the E484K mutation, and so these numbers may not hold going forward.
Over the past couple of months we've looked at a number of other studies on reinfection with SARS-CoV-2, including:
UK: Oxford Launches Human Challenge Trial To Study Immune Response To COVID-19
MMWR: Suspected SARS-CoV-2 Reinfections Among Residents Of A Skilled Nursing Facility - Kentucky, Jul.- Nov. 2020
Brazil MOH Confirms Reinfection With COVID Variant P.1 In Amazonas
The Lancet: Resurgence of COVID-19 in Manaus, Brazil, Despite High Seroprevalence
All of which brings us to a new report, published yesterday in the CDC's EID Journal, that looks at COVID reinfections among 4 healthcare workers in Brazil during 2020, including their clinical course, and analysis of viral shedding.
Of note, none of these reinfections involved the B.1.1.7, P.1, P.2 or any other recognized VOC (Variant of Concern).
While you'll want to read the complete report (below), the takeaway is that prior infection doesn't necessarily produce durable immunity. Anyone who eschews masks, social distancing, or the vaccine because they've already had COVID - and assume themselves to be immune - could have a nasty surprise ahead.
I've only reproduced some excerpts from the report, so follow the link to read it (and the accompanying files) in their entirety.
Research Letter
Respiratory Viral Shedding in Healthcare Workers Reinfected with SARS-CoV-2, Brazil, 2020
Figure Table Appendix RIS [TXT - 2 KB]
Mariene R. Amorim1, William M. Souza1, Antonio C.G. Barros, Daniel A. Toledo-Teixeira, Karina Bispo dos-Santos, Camila L. Simeoni, Pierina L. Parise, Aline Vieira, Julia Forato, Ingra M. Claro, Luciana S. Mofatto, Priscilla P. Barbosa, Natalia S. Brunetti, Emerson S.S. França, Gisele A. Pedroso, Barbara F.N. Carvalho, Tania R. Zaccariotto, Kamila C.S. Krywacz, André S. Vieira, Marcelo A. Mori, Alessandro S. Farias, Maria H.P. Pavan, Luís Felipe Bachur, Luís G.O. Cardoso, Fernando R. Spilki, Ester C. Sabino, Nuno R. Faria, Magnun N.N. Santos, Rodrigo N. Angerami, Patricia A.F. Leme, Angelica Schreiber, Maria L. Moretti, Fabiana Granja, and José Luiz Proenca-Modena
AbstractWe documented 4 cases of severe acute respiratory syndrome coronavirus 2 reinfection by non–variant of concern strains among healthcare workers in Campinas, Brazil. We isolated infectious particles from nasopharyngeal secretions during both infection episodes. Improved and continued protection measures are necessary to mitigate the risk for reinfection among healthcare workers.Coronavirus disease (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged in Wuhan, China, in late 2019. As of April 8, 2021, COVID-19 has affected >132 million persons and caused >2.87 million deaths around the world (https://covid19.who.int).Whether the immune response elicited by an initial infection protects against reinfection is uncertain. The Pan American Health Organization provisionally defines reinfection as a positive SARS-CoV-2 test result >45 days after initial infection, given that other infections and prolonged shedding of SARS-CoV-2 or viral RNA have been ruled out (1). Healthcare workers (HCWs) are consistently exposed to SARS-CoV-2 and are therefore susceptible to reinfection.We investigated 4 cases of SARS-CoV-2 reinfection among HCWs at the Hospital das Clínicas da Unicamp, a tertiary public hospital at the University of Campinas (Campinas, Brazil). This study was approved by the Research Ethical Committee of the University of Campinas (approval no. CAAE-31170720.3.0000.5404). The 4 HCWs, consisting of 3 nurses and 1 staff member, were women with an average age of 44 years (range 40–61 years) (Figure 1, panel A).For the initial infections, symptom onset ranged from April 5–May 10, 2020, and lasted 10–23 days. We identified SARS-CoV-2 RNA in nasopharyngeal swab samples using real-time quantitative reverse transcription PCR (qRT-PCR) 2–4 days after symptom onset (2). All 4 HCWs had mild COVID-19 signs and symptoms and recovered (Table). After signs and symptoms resolved, the HCWs tested negative by qRT-PCR, Elecsys Anti-SARS-CoV-2 (Roche Diagnostics, https://diagnostics.roche.com), or both.Reinfection, confirmed by a nucleic acid amplification test using the GeneFinder COVID-19 Plus RealAmp Kit (3), developed 55–170 days after symptom onset of the first infection. Signs and symptoms of reinfection lasted 9–23 days. Only 1 HCW had a concurrent condition (chronic bronchitis), and none were immunosuppressed.None required hospitalization during the initial or reinfection episodes (Table). After recovering from their initial infections, all HWCs continued to use the same types of personal protective equipment (i.e., disposable surgical masks, gloves, gowns, and goggles) in accordance with recommendations from the Ministry of Health of Brazil (https://coronavirus.saude.gov.br/saude-e-seguranca-do-trabalhador-epi).To assess whether infectious SARS-CoV-2 particles were shed in nasopharyngeal secretions during both COVID-19 episodes, we conducted viral isolation in Vero cells (ATCC no. CCL-81) (W.M. de Souza, unpub. data, https://dx.doi.org/10.2139/ssrn.3793486) (Appendix). We inoculated Vero cells with isolated SARS-CoV-2 virions from nasopharyngeal swab samples collected during the first and second infections; we observed a cytopathic effect 3–4 days after inoculation. On day 4, we obtained cell culture supernatant by centrifugation and conducted qRT-PCR selective for the envelope gene to confirm the presence of SARS-CoV-2 RNA; we found the supernatants had 2.8 × 102–1.4 × 1010 RNA copies/mL (2). We confirmed viral isolation by the increased number of RNA copies per milliliter and the decreased cycle threshold values after passage into Vero cells. The isolation of SARS-CoV-2 shows that nasopharyngeal swab samples contained infectious particles during both COVID-19 episodes.(SNIP)In conclusion, we report cases of SARS-CoV-2 reinfection among HCWs. We observed the shedding of infectious viral particles during both infection episodes of each HCW. Hence, the continuation of protective measures, as well as efforts to monitor, track exposures, and identify areas at high risk for infection, are critical to reducing SARS-CoV-2 reinfection, especially among HCWs.Ms. Amorim is a doctoral candidate at the Department of Genetics, Evolution, Microbiology and Immunology at the University of Campinas, Brazil. Her research interests include genomic sequencing and epidemiologic surveillance of emerging viruses in Brazil.
