SARS-CoV-2 Delta-variant breakthrough infections in nursing home residents at midterm after Comirnaty® COVID-19 vaccination

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Delta variant breakthrough infections in nursing home residents following vaccination with Comirnaty® COVID-19 vaccine were characterized. In total, 201 participants (median age, 87 years; range, 64-100; 133 female) from two nursing homes in the Valencian community (Spain) were included. SARS-CoV-2-Spike (S) antibody responses were determined by a lateral flow immunocromatography (LFIC) assay and by quantitative electrochemiluminescent assay in LFIC-negative participants. SARS-CoV-2-S-IFNγ T cells were enumerated by flow cytometry in 10 participants. Nasopharyngeal SARS-CoV-2 RNA loads were quantified by real-time polymerase chain reaction assays. Vaccine breakthrough COVID-19 due to the Delta variant occurred in 39 residents (median age, 87 years; range, 69-96; 31 female) at a median of 6.5 months after vaccination (nine requiring hospitalization). Breakthrough infections occurred at a higher rate (p < 0.0001) in residents who had not been previously infected with SARS-CoV-2 (naïve) (33/108; 18%) than in those with prior diagnosis of SARS-CoV-2 infection (experienced) (6/93; 6.4%), and were more likely (p < 0.0001) to develop in residents who tested negative by LFIC (20/49) at 3 months after vaccination as compared to their LFIC-positive counterparts (19/142). Among LFIC-negative residents, a trend towards lower plasma anti-RBD antibody levels was noticed in those developing breakthrough infection (p = 0.16). SARS-CoV-2 RNA loads in nasopharyngeal specimens were lower in SARS-CoV-2-experienced residents (p < 0.001) and in those testing positive by LFIC (p = 0.13). The frequency of SARS-CoV-2-S-reactive T cells at 3 months was similar in LFIC-negative residents with (n = 7) or without (n = 3) breakthrough infection. Prior history of SARS-CoV-2 infection and detection of S-reactive antibodies by LFIC at 3 months is associated with a lower risk of Delta-variant breakthrough infection in nursing home residents at midterm after Comirnaty® COVID-19 vaccination.

Keywords: Comirnaty® COVID-19 vaccine; SARS-CoV-2 Delta variant; anti-spike antibodies; breakthrough infection; nursing home residents; spike-reactive T cells.

Figure 1

Box‐whisker plots representing SARS‐CoV‐2 RNA load in nasopharyngeal specimens as measured by commercial RT‐PCR assays calibrated to the AMPLIRUN® TOTAL SARS‐CoV‐2 RNA Control (Vircell SA), according to (A) SARS‐CoV‐2 infection status of participants with breakthrough infection before outbreak declaration (naïve; n = 33; experienced, n = 6) or (B) presence or absence of detectable anti‐S IgGs by a lateral flow immunochromatography (OnSite COVID‐19 IgG/IgM Rapid Test; CTK BIOTECH) in whole blood obtained by fingerstick at 3 months following complete vaccination with the Comirnaty® COVID‐19 vaccine in 39 nursing home residents. The p value is shown for comparisons. COVID‐19, coronavirus disease 2019; RT‐PCR, real‐time polymerase chain reaction; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2

Figure 2

Box‐whisker plots depicting SARS‐CoV‐2 S receptor‐binding domain (RBD) total antibody levels as measured at 3 months following complete vaccination with the Comirnaty® COVID‐19 vaccine by the Roche Elecsys® Anti‐SARS‐CoV‐2 S (Roche Diagnostics, Pleasanton) in 49 nursing home residents testing negative by a lateral flow immunochromatography (OnSite COVID‐19 IgG/IgM Rapid Test; CTK BIOTECH) in whole blood obtained by fingerstick, either subsequently developing a breakthrough infection or not. The p value is shown for comparison. COVID‐19, coronavirus disease 2019; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2