Volume 70, Issue 3 p. 659-668
Clinical Investigation

Evaluating immunity to SARS-CoV-2 in nursing home residents using saliva IgG

Morgan J. Katz MD

Corresponding Author

Morgan J. Katz MD

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

Correspondence

Morgan J. Katz and Clare Rock, Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, 5200 Eastern Ave, Mason F. Lord Building, Center Tower, Ste. 360, Baltimore, Maryland 21224, USA.

Email: [email protected] and [email protected]

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Christopher D. Heaney PhD

Christopher D. Heaney PhD

Department of Environmental Health and Engineering, Epidemiology and International Health Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

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Nora Pisanic PhD

Nora Pisanic PhD

Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

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Leigh Smith MD

Leigh Smith MD

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

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Benjamin F. Bigelow MD

Benjamin F. Bigelow MD

Johns Hopkins Medicine COVID Testing, The Johns Hopkins Medical Institutions, Baltimore, Maryland, USA

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Fatima Sheikh MD

Fatima Sheikh MD

Division of Geriatric Medicine and Gerontology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

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Alec Boudreau BS

Alec Boudreau BS

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

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Kate Kruczynski PhD

Kate Kruczynski PhD

Department of Environmental Health and Engineering, Epidemiology and International Health Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

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Yea-Jen Hsu PhD

Yea-Jen Hsu PhD

Department of Health Policy and Management, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA

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Alejandra B. Salinas BS

Alejandra B. Salinas BS

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

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Sara E. Cosgrove MD, MS

Sara E. Cosgrove MD, MS

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

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Clare Rock MD

Corresponding Author

Clare Rock MD

Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA

Correspondence

Morgan J. Katz and Clare Rock, Division of Infectious Diseases, Department of Medicine, Johns Hopkins University School of Medicine, 5200 Eastern Ave, Mason F. Lord Building, Center Tower, Ste. 360, Baltimore, Maryland 21224, USA.

Email: [email protected] and [email protected]

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First published: 17 January 2022
Citations: 6

Funding information: This work was supported by the Centers for Disease Control and Prevention's Prevention Epicenter Program through a COVID-19 supplement [grant number 6 U01CK000554-02-02]. The content is solely the responsibility of the authors and does not necessarily represent the official view of the funding agency.

Abstract

Background

SARS-CoV-2 circulating variants coupled with waning immunity pose a significant threat to the long-term care (LTC) population. Our objective was to measure salivary IgG antibodies in residents and staff of an LTC facility to (1) evaluate IgG response in saliva post-natural infection and vaccination and (2) assess its feasibility to describe the seroprevalence over time.

Methods

We performed salivary IgG sampling of all residents and staff who agreed to test in a 150-bed skilled nursing facility during three seroprevalence surveys between October 2020 and February 2021. The facility had SARS-CoV-2 outbreaks in May 2020 and November 2020, when 45 of 138 and 37 of 125 residents were infected, respectively; they offered two Federal vaccine clinics in January 2021. We evaluated quantitative IgG in saliva to the Nucleocapsid (N), Spike (S), and Receptor-binding domain (RBD) Antigens of SARS-CoV-2 over time post-infection and post-vaccination.

Results

One hundred twenty-four residents and 28 staff underwent saliva serologic testing on one or more survey visits. Over three surveys, the SARS-CoV-2 seroprevalence at the facility was 49%, 64%, and 81%, respectively. IgG to S, RBD, and N Antigens all increased post infection. Post vaccination, the infection naïve group did not have a detectable N IgG level, and N IgG levels for the previously infected did not increase post vaccination (p < 0.001). Fully vaccinated subjects with prior COVID-19 infection had significantly higher RBD and S IgG responses compared with those who were infection-naïve prior to vaccination (p < 0.001 for both).

Conclusions

Positive SARS-COV-2 IgG in saliva was concordant with prior infection (Anti N, S, RBD) and vaccination (Anti S, RBD) and remained above positivity threshold for up to 9 months from infection. Salivary sampling is a non-invasive method of tracking immunity and differentiating between prior infection and vaccination to inform the need for boosters in LTC residents and staff.

CONFLICT OF INTEREST

The authors declare no pertinent conflict of interest.