COVID-19: Seroprevalence and Vaccine Responses in UK Dental Care Professionals

Abstract

Dental care professionals (DCPs) are thought to be at enhanced risk of occupational exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, robust data to support this from large-scale seroepidemiological studies are lacking. We report a longitudinal seroprevalence analysis of antibodies to SARS-CoV-2 spike glycoprotein, with baseline sampling prior to large-scale practice reopening in July 2020 and follow-up postimplementation of new public health guidance on infection prevention control (IPC) and enhanced personal protective equipment (PPE). In total, 1,507 West Midlands DCPs were recruited into this study in June 2020. Baseline seroprevalence was determined using a combined IgGAM enzyme-linked immunosorbent assay and the cohort followed longitudinally for 6 mo until January/February 2021 through the second wave of the coronavirus disease 2019 pandemic in the United Kingdom and vaccination commencement. Baseline seroprevalence was 16.3%, compared to estimates in the regional population of 6% to 7%. Seropositivity was retained in over 70% of participants at 3- and 6-mo follow-up and conferred a 75% reduced risk of infection. Nonwhite ethnicity and living in areas of greater deprivation were associated with increased baseline seroprevalence. During follow-up, no polymerase chain reaction-proven infections occurred in individuals with a baseline anti-SARS-CoV-2 IgG level greater than 147.6 IU/ml with respect to the World Health Organization international standard 20-136. After vaccination, antibody responses were more rapid and of higher magnitude in those individuals who were seropositive at baseline. Natural infection with SARS-CoV-2 prior to enhanced PPE was significantly higher in DCPs than the regional population. Natural infection leads to a serological response that remains detectable in over 70% of individuals 6 mo after initial sampling and 9 mo from the peak of the first wave of the pandemic. This response is associated with protection from future infection. Even if serological responses wane, a single dose of the Pfizer-BioNTech 162b vaccine is associated with an antibody response indicative of immunological memory.

Keywords: SARS-CoV-2; antibodies; dentistry; occupational exposure; seroepidemiological studies; vaccination.

Figure 1.

Participant flowchart through the study alongside headline serological data. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Figure 2.

Longitudinal seroprevalence and vaccine responses in dental care professionals. (A) Total anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein antibodies (Total GAM) and IgG and IgA anti–SARS-CoV-2 spike glycoprotein antibodies measured at baseline and 3-mo and 6-mo follow up. At 6 mo, only individuals who had not been vaccinated are shown. Data are provided as a ratio of the level of antibody compared to the cutoff calibrator set at 1.0. Percentages of individuals above the assay cutoff at each time point are also provided above each column with 95% confidence intervals provided below in parentheses. Median and 95% confidence intervals are also shown. (B) Receiver operator characteristic curve describing the relationship between baseline anti–SARS-CoV-2 spike glycoprotein IgG ratio and binary IgG seropositivity/seronegativity in unvaccinated, non-reinfected individuals at 6-mo follow up. Area under the curve = 0.77, P = 0.01 (n = 75). (C) International reference materials NIBSC 20-136 (World Health Organization) and 20-162 were run in triplicate serial dilutions and the IgG ratio determined. The minimum IgG ratio associated with guaranteed ongoing seropositivity 6 mo from baseline is shown by the red and blue dotted lines. (D) Kinetics of total antibody response in 490 individuals following a single dose of the Pfizer-BioNTech vaccine. *Demonstrates a significant difference (P < 0.05) between the distributions of IgGAM ratios at each time point following vaccination between individuals who were seropositive and seronegative at baseline as determined by Kolmogorov–Smirnov test. Percentage of individuals above the assay cutoff at each time point is also provided.