Post-vaccination SARS-cov-2 infection in nursing home residents, Bordeaux, France

Abstract

Objective: To describe COVID-19 breakthrough infections in two nursing homes (NHs) sites of active COVID-19 clusters despite optimal vaccination coverage.

Methods: A cross-sectional study was conducted in two NHs of south-western France, following the investigation of COVID-19 clusters (February-March 2021). SARS-CoV-2-confirmed infection was defined by positive RT-PCR. Antibodies neutralization capacities were tested in a subgroup of fully-vaccinated and seropositive-residents.

Results: Of the 152 residents, 66% were female with median age 87 years (IQR: 80.0-90.2). Overall, 132 (87%) residents received 2 doses of vaccine, 14 (9%) one dose and 6 (4%) were unvaccinated. Forty-seven (31%) residents had confirmed infection (45 (98%) with variant 20I/501Y.V1). All 6 non-vaccinated residents, 4 /14 who had one dose and 37/132 that had two doses, were infected. Of the 39 residents reporting symptoms, 12 and 3 presented severe and critical disease, respectively. One resident with a confirmed infection died. Infected-residents had a median anti-S IgG titre of 19 116.0 (IQR: 3 028.0-39 681.8 AU/mL), 19 times higher than that of non-infected vaccinated persons (1,207.0; IQR: 494.0-2,782.0). In the subgroup of 19 residents tested for neutralizing antibodies, the neutralizing titre (50%) was strongly positively correlated with the anti-S IgG titre (correlation coefficient = 0.83), and 1.5 times higher for the infected than non-infected residents [5.9 (IQR: 5.3-6.9) vs. 3.6 (2.9-3.8)].

Conclusion: Institutionalized elderly persons who undergo breakthrough infection develop higher titres of anti-S IgGs, which are strongly correlated with the neutralizing capacity of the antibodies. These results advocate for additional vaccine doses in this population.

Keywords: COVID-19; Neutralizing antibodies; SARS-CoV-2, Nursing homes; Vaccine.

Fig. 1

Distribution of anti-S IgG antibody titre and neutralizing antibody (Nab) titre with 50% inhibition. A total of 151 NH residents had available anti-S IgG titre, and 19 had available neutralizing antibodies (NAb) titre. An aberrant neutralizing test result for 1 non-infected patient was not included. (a) Anti-S IgG antibody titre in 151 NH residents according to the RT-PCR test results; (b) anti-S IgG antibody titre in 151 nursing home residents according to the RT-PCR test result, stratified by vaccine status; (c) NAb titre with 50% inhibition in 19 selected NH residents according to the RT-PCR test result; (d) correlation between NAb titre with 50% inhibition (NT50%) and anti-S IgG titre in 19 selected NH residents tested for NAb titre. Figures (a)–(c) display boxplots showing the distribution of anti-S IgG antibody titre and NAb titre with 50% inhibition in selected residents. Boxes with central horizontal lines indicate the median of the titre on a log-10 scale; the boxes’ lower limit is the 25th percentile and the upper limit is the 75th percentile. The vertical lines indicate 1.5 times the interquartile range. Two-tailed P-values were determined using the Wilcoxon-Mann-Whitney test, with Bonferroni correction for stratified analyses. In (d), the r and P-values are from two-tailed Spearman's correlation.