Strong Decay of SARS-CoV-2 Spike Antibodies after 2 BNT162b2 Vaccine Doses and High Antibody Response to a Third Dose in Nursing Home Residents.

OBJECTIVES: To measure the antibody decay after 2 BNT162b2 doses and the antibody response after a third vaccine dose administered 6 months after the second one in nursing home residents with and without prior COVID-19. DESIGN: Cohort study. SETTING AND PARTICIPANTS: Four hundred-eighteen residents from 18 nursing homes. METHODS: Blood receptor-binding domain (RBD)-IgG (IgG II Quant assay, Abbott Diagnostics; upper limit: 5680 BAU) and nucleocapsid-IgG (Abbott Alinity) were measured 21‒28 days after the second BNT162b2 dose, as well as 1‒3 days before and 21‒28 days after the third vaccine dose. RBD-IgG levels of ≥592 BAU/mL were considered as high antibody response. Residents with prior positive quantitative reverse transcription polymerase chain reaction on a nasopharyngeal swab or with N-IgG levels above 0.8 S/CO were considered as prior COVID-19 residents. RESULTS: In prior COVID-19 residents (n = 122), RBD-IgG median levels decreased by 82% in 167 days on average. In the same period, the number of residents with a high antibody response decreased from 88.5% to 54.9% (P < .0001) and increased to 97.5% after the third vaccine dose (P = .02 vs the first measure). In residents without prior COVID-19 (n = 296), RBD-IgG median levels decreased by 89% in 171 days on average. The number of residents with a high antibody response decreased from 29.4% to 1.7% (P < .0001) and increased to 88.4% after the third vaccine dose (P < .0001 vs the first measure). CONCLUSIONS AND IMPLICATIONS: The strong and rapid decay of RBD-IgG levels after the second BNT162b2 dose in all residents and the high antibody response after the third dose validate the recommendation of a third vaccine dose in residents less than 6 months after the second dose, prioritizing residents without prior COVID-19. The slope of RBD-IgG decay after the third BNT162b2 dose and the protection level against SARS-CoV-2 B.1.1.529 (omicron) and other variants of concern provided by the high post-boost vaccination RBD-IgG response require further investigation in residents.

Receptor binding domain-IgG levels correlate with protection in residents facing SARS-CoV-2 B.1.1.7 outbreaks.

BACKGROUND: Limited information exists on nursing home (NH) residents regarding BNT162b2 vaccine efficacy in preventing SARS-CoV-2 and severe COVID-19, and its association with post-vaccine humoral response. METHODS: 396 residents from seven NHs suffering a SARS-CoV-2 B.1.1.7 (VOC-α) outbreak at least 14 days after a vaccine campaign were repeatedly tested using SARS-CoV-2 real-time reverse-transcriptase polymerase chain reaction on nasopharyngeal swab test (RT-qPCR). SARS-CoV-2 receptor-binding domain (RBD) of the S1 subunit (RBD-IgG) was measured in all residents. Nucleocapsid antigenemia (N-Ag) was measured in RT-qPCR-positive residents and serum neutralizing antibodies in vaccinated residents from one NH. RESULTS: The incidence of positive RT-qPCR was lower in residents vaccinated by two doses (72/317; 22.7%) vs one dose (10/31; 32.3%) or non-vaccinated residents (21/48; 43.7%; p < .01). COVID-19-induced deaths were observed in 5 of the 48 non-vaccinated residents (10.4%), in 2 of the 31 who had received one dose (6.4%), and in 3 of the 317 (0.9%) who had received two doses (p = .0007). Severe symptoms were more common in infected non-vaccinated residents (10/21; 47.6%) than in infected vaccinated residents (15/72; 21.0%; p = .002). Higher levels of RBD-IgG (n = 325) were associated with a lower SARS-CoV-2 incidence. No in vitro serum neutralization activity was found for RBD-IgG levels below 1050 AU/ml. RBD-IgG levels were inversely associated with N-Ag levels, found as a risk factor of severe COVID-19. CONCLUSIONS: Two BNT162b2 doses are associated with a 48% reduction of SARS-CoV-2 incidence and a 91.3% reduction of death risk in residents from NHs facing a VOC-α outbreak. Post-vaccine RBD-IgG levels correlate with BNT162b2 protection against SARS-CoV-2 B.1.1.7.

Antibody response after one and two jabs of the BNT162b2 vaccine in nursing home residents: The CONsort-19 study.

BACKGROUND: The humoral immune response following COVID-19 vaccination in nursing home residents is poorly known. A longitudinal study compared levels of IgG antibodies against the spike protein (S-RBD IgG) (S-RDB protein IgG) after one and two BNT162b2/Pfizer jabs in residents with and without prior COVID-19. METHODS: In 22 French nursing homes, COVID-19 was diagnosed with real-time reverse-transcriptase polymerase chain reaction (RT-PCR) for SARS-CoV-2. Blood S-RDB-protein IgG and nucleocapsid (N) IgG protein (N-protein IgG) were measured 21-24 days after the first jab (1,004 residents) and 6 weeks after the second (820 residents). RESULTS: In 735 residents without prior COVID-19, 41.7% remained seronegative for S-RDB-protein IgG after the first jab vs. 2.1% of the 270 RT-PCR-positive residents (p < 0.001). After the second jab, 3% of the 586 residents without prior COVID-19 remained seronegative. However, 26.5% had low S-RDB-protein IgG levels (50-1050 UA/ml) vs. 6.4% of the 222 residents with prior COVID-19. Residents with an older infection (first wave), or with N-protein IgG at the time of vaccination, had the highest S-RDB-protein IgG levels. Residents with a prior COVID-19 infection had higher S-RDB-protein IgG levels after one jab than those without after two jabs. INTERPRETATION: A single vaccine jab is sufficient to reach a high humoral immune response in residents with prior COVID-19. Most residents without prior COVID-19 are seropositive for S-RDB-protein IgG after the second jab, but around 30% have low levels. Whether residents with no or low post-vaccine S-RDB protein IgG are at higher risk of symptomatic COVID-19 requires further analysis.

Atypical symptoms, SARS-CoV-2 test results and immunisation rates in 456 residents from eight nursing homes facing a COVID-19 outbreak.

BACKGROUND: Frail older persons may have an atypical presentation of coronavirus disease 2019 (COVID-19). The value of real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) testing for identifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nursing homes (NHs) residents is not known. OBJECTIVE: To determine whether (i) atypical symptoms may predict rRT-PCR results and (ii) rRT-PCR results may predict immunisation against SARS-CoV-2 in NH residents. DESIGN: A retrospective longitudinal study. SETTING: Eight NHs with at least 10 rRT-PCR-positive residents. SUBJECTS: A total of 456 residents. METHODS: Typical and atypical symptoms recorded in residents' files during the 14 days before and after rRT-PCR testing were analysed. Residents underwent blood testing for IgG-SARS-CoV-2 nucleocapsid protein 6 to 8 weeks after testing. Univariate and multivariate analyses compared symptoms and immunisation rates in rRT-PCR-positive and negative residents. RESULTS: A total of 161 residents had a positive rRT-PCR (35.3%), 17.4% of whom were asymptomatic before testing. Temperature >37.8°C, oxygen saturation <90%, unexplained anorexia, behavioural change, exhaustion, malaise and falls before testing were independent predictors of a further positive rRT-PCR. Among the rRT-PCR-positive residents, 95.2% developed SARS-CoV-2 antibodies vs 7.6% in the rRT-PCR-negative residents. Among the residents with a negative rRT-PCR, those who developed SARS-CoV-2 antibodies more often had typical or atypical symptoms (P = 0.02 and <0.01, respectively). CONCLUSION: This study supports a strategy based on (i) testing residents with typical or unexplained atypical symptoms for an early identification of the first SARS-CoV-2 cases, (ii) rT-PCR testing for identifying COVID-19 residents, (iii) repeated wide-facility testing (including asymptomatic cases) as soon as a resident is tested positive for SARS-CoV-2 and (iv) implementing SARS-CoV-2 infection control measures in rRT-PCR-negative residents when they have unexplained typical or atypical symptoms.