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Severe acute respiratory coronavirus virus 2 (SARS-CoV-2) infection in asymptomatic vaccinated healthcare workers

Published online by Cambridge University Press:  10 May 2021

Verena Damiani
Affiliation:
Dipartimento di Tecnologie Innovative in Medicina & Odontoiatria, G. d’Annunzio University of Chieti-Pescara, Italy Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Domitilla Mandatori
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy Dipartimento di Scienze Mediche, Orali e Biotecnologiche, G. d’Annunzio University of Chieti-Pescara, Italy
Simone De Fabritiis
Affiliation:
Dipartimento di Tecnologie Innovative in Medicina & Odontoiatria, G. d’Annunzio University of Chieti-Pescara, Italy Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Sandra Bibbò
Affiliation:
Dipartimento di Tecnologie Innovative in Medicina & Odontoiatria, G. d’Annunzio University of Chieti-Pescara, Italy Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Rossella Ferrante
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy Dipartimento di Scienze Psicologiche, della Salute e del Territorio, G. d’Annunzio University of Chieti-Pescara, Italy
Fabrizio Di Giuseppe
Affiliation:
Dipartimento di Tecnologie Innovative in Medicina & Odontoiatria, G. d’Annunzio University of Chieti-Pescara, Italy Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Anna Giulia Ruggieri
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Carola Di Camillo
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Carlotta Buccolini
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
Dora Pizzi
Affiliation:
Dipartimento di Microbiologia e Virologia, University of Chieti-Pescara, S. Spirito Hospital of Pescara, Pescara, Italy
Paolo Fazii
Affiliation:
Dipartimento di Microbiologia e Virologia, University of Chieti-Pescara, S. Spirito Hospital of Pescara, Pescara, Italy
Liborio Stuppia*
Affiliation:
Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy Dipartimento di Scienze Psicologiche, della Salute e del Territorio, G. d’Annunzio University of Chieti-Pescara, Italy
Vincenzo De Laurenzi
Affiliation:
Dipartimento di Tecnologie Innovative in Medicina & Odontoiatria, G. d’Annunzio University of Chieti-Pescara, Italy Center for Advanced Studies and Technology (CAST), G. d’Annunzio University of Chieti-Pescara, Italy
*
Author for correspondence: Professor Liborio Stuppia, E-mail: stuppia@unich.it
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Abstract

Type
Research Brief
Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s), 2021. Published by Cambridge University Press on behalf of The Society for Healthcare Epidemiology of America

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused >2.7 million deaths worldwide, 1 devasting health systems end economies worldwide. Since the first months of the pandemic, a rapid and massive effort has been performed by the scientific community to develop a safe and effective vaccine against SARS-CoV-2. Reference Su, Du and Jiang2 In Italy, the first population to receive the vaccine was healthcare workers (HCWs) who are principally exposed to SARS-CoV-2 infection during the management of coronavirus disease 2019 (COVID-19) patients. Reference Moore, Rickard and Stevenson3 Several doubts remain concerning the neutralizing properties of antibodies produced after vaccination. Reference Sahin, Muik and Derhovanessian4 Moreover, little is known about transient infections in vaccinated individuals who therefore could be potential carriers of the disease. Reference Dan, Mateus and Kato5 Finally, it is important to understand the actual efficacy of the approved vaccines against SARS-CoV-2 variants, which have led to enhanced virus transmissibility, morbidity, and mortality. Reference Davies and Jarvis6,Reference Challen, Brooks-Pollock, Read, Dyson, Tsaneva-Atanasova and Danon7

Here, we report several asymptomatic and vaccinated HCWs who tested positive for SARS-CoV-2 during surveillance testing.

Methods

Samples

Approximately 500 nasopharyngeal swab specimens of HCWs and hospitalized patients were collected at the Hospital Ss. Annunziata of Chieti, Italy, and analyzed by the Laboratory of Molecular Genetics Test Diagnosis COVID-19 of the Center for Advanced Studies and Technology (CAST) at Gabriele d’Annunzio University of Chieti-Pescara, Italy.

RNA extraction and qRT-PCR

RNA was extracted from nasopharyngeal specimens, using the MagMAX Viral/Pathogen II Nucleic Acid Isolation Kit on the automated KingFisher processor (Thermo Fisher Scientific, Waltham, MA). The extracted RNA underwent real-time reverse transcription polymerase chain reaction (qRT-PCR) with 2 commercial kits: the TaqPath COVID-19 CE-IVD RT-PCR Kit assay (Thermo Fisher Scientific) and Allplex SARS-CoV-2 Variants I Assay (Seegene, Korea).

Next-generation sequencing (NGS)

For whole viral genome sequencing, total RNA was reverse transcribed using Invitrogen SuperScript VILO cDNA Synthesis Kit (Thermo Fisher Scientific). cDNA libraries were prepared using the Ion AmpliSeq SARS-CoV-2 Research Panel (Thermo Fisher Scientific). Sequencing was performed on the Ion GeneStudio S5 System (Thermo Fisher Scientific). The consensus sequences were aligned with the Wuhan-Hu reference SARS-CoV-2 genome using the Torrent Suite platform (Thermo Fisher Scientific). For phylogenetic analysis the whole-genome sequences of the isolates were uploaded on Pangolin COVID-19 Lineage Assigner. 8

Results

From January to March 2021, we were informed that among those who tested positive for SARS-CoV-2, 7 were HCWs who had received the BNT162b2 vaccination (Table 1). All were contacted and gave informed consent for this study.

Table 1. Vaccination Status, qRT-PCR Results, and NGS Summary

Note. qRT-PCR, real-time reverse transcription polymerase chain reaction; NGS, next-generation sequencing of the entire viral genome; ID, study identification number; HCW, healthcare worker; Ct, cycle threshold; ORF, open reading frame; N, nucleocapsid; S, spike; ND, Ct value not determined.

a Allplex indicates that the presence of Δ69/70, N501Y and E484K were evaluated using Allplex SARS-CoV-2 variants I assay.

Of these 7 HCWs, 6 had received both doses of the vaccine and 1 had received only the first dose. HCWs 2, 4, and 5 received positive SARS-COV-2 results between 3 and 8 days after receiving the second dose. The remaining 3 cases (HCWs 3, 6, and 7) received positive results between 23 and 36 days after the administration of the second dose of vaccine.

All HCWs were completely asymptomatic and had undergone testing in a routine surveillance schedule for HCWs. In 3 cases, we were able to retest the HCWs the day after the positive qRT-PCR result and show that they were already negative. The remaining cases were tested after 10 days, and all were negative for SARS-CoV-2 infection.

In all 7 cases, molecular tests showed the presence of the Δ69/70 deletion of the S gene found in the B.1.1.7 lineage known as the UK variant, indicated by the TaqPath kit, which fails to amplify the S gene in the presence of the Δ69/70 deletion. Reference Kidd, Richter and Best9

The NGSs of the viral genomes of HCWs 1, 2, and 3 confirmed that the infections belonged to the B.1.1.7 lineage. The remaining cases (HCWs 4, 5, 6, and 7) were tested using the Allplex Assay, which confirmed the presence of the Δ69/70 deletion and of the N501Y mutation, thus confirming that these cases belonged to the B.1.1.7 lineage.

Discussion

Data collected in this study confirm that infection is possible following vaccination. In 1 case, this was expected because the infection occurred only a few days after the administration of the first dose of vaccine, likely before the production of antibodies. Indeed, it has been reported that neutralizing antibody levels start to increase 8 days after the first dose of vaccine reaching the peak 2 weeks after the boost of the second dose. Reference Sahin, Muik and Derhovanessian4 The infection that occurred in 3 HCWs a few days after the administration of the second dose may have been due to the weak titer of neutralizing antibodies produced.

The last 3 cases show that some individuals can still be infected after having completed the vaccination schedule and after sufficient time has passed for the peak of antibody production to occur. Unfortunately, we were not able to evaluate antibody levels at the time of infection; therefore, we were unable to correlate infection with low antibody titer.

Finally, all of the cases we observed in this report were due B.1.1.7 lineage infection. Although we cannot draw conclusions due to the limited numbers of cases observed so far, we can confirm that the vaccine has an effect on this variant because none of the infected individuals showed symptoms and all rapidly became SARS-CoV-2 negative.

In conclusion, although further data and observations of larger cohorts are needed, we strongly believe that continued attention should be devoted to the problem of infection in vaccinated people. Our data demonstrate that some people can have transient asymptomatic infections following vaccination and can therefore be potentially infectious, thus suggesting the necessity of precaution to be maintained particularly for HCWs to avoid spreading the virus, particularly among hospitalized people.

Acknowledgments

We would like to thank Michele Scanzano, Nada Ramundi and Carol Polidoro of the Biblos service of Pescara for their assistance in data collection.

Financial support

No financial support was provided relevant to this article.

Conflicts of interest

All authors report no conflicts of interest relevant to this article.

References

Coronavirus (COVID-19) dashboard. World Health Organization website. https://covid19.who.int/. Accessed May 5, 2021.Google Scholar
Su, S, Du, L, Jiang, S. Learning from the past: development of safe and effective COVID-19 vaccines. Nat Rev Microbiol 2020;19:211219.CrossRefGoogle ScholarPubMed
Moore, G, Rickard, H, Stevenson, D, et al. Detection of SARS-CoV-2 within the healthcare environment: a multicentre study conducted during the first wave of the COVID-19 outbreak in England. J Hosp Infect 2021;108:189196.CrossRefGoogle ScholarPubMed
Sahin, U, Muik, A, Derhovanessian, E, et al. COVID-19 vaccine BNT162b1 elicits human antibody and TH1 T cell responses. Nature 2020;586:594599.CrossRefGoogle ScholarPubMed
Dan, JM, Mateus, J, Kato, Y, et al. Immunological memory to SARS-CoV-2 assessed for up to 8 months after infection. Science 2021;371(6529). doi: 10.1126/science.abf4063.CrossRefGoogle Scholar
Davies, NG, Jarvis, CI, et al for the CMMID COVID-19 Working Group. Increased mortality in community-tested cases of SARS-CoV-2 lineage B.1.1.7. Nature 2021. doi: 10.1038/s41586-021-03426-1.CrossRefGoogle Scholar
Challen, R, Brooks-Pollock, E, Read, JM, Dyson, L, Tsaneva-Atanasova, K, Danon, L. Risk of mortality in patients infected with SARS-CoV-2 variant of concern 202012/1: matched cohort study. BMJ 2021;372:n579.CrossRefGoogle ScholarPubMed
Cov-lineages/pangolin: software package for assigning SARS-CoV-2 genome sequences to global lineages. Github website. https://github.com/cov-lineages/pangolin. Accessed May 5, 2021.Google Scholar
Kidd, M, Richter, A, Best, A, et al. S-variant SARS-CoV-2 lineage B1.1.7 is associated with significantly higher viral loads in samples tested by ThermoFisher TaqPath RT-qPCR. J Infect Dis 2021. doi: 10.1093/infdis/jiab082.CrossRefGoogle Scholar
Figure 0

Table 1. Vaccination Status, qRT-PCR Results, and NGS Summary

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