Frailty impacts immune responses to Moderna COVID-19 mRNA vaccine in older adults

Age-related changes in the immune system and challenges for the development of age-specific vaccines

BACKGROUND

A better understanding of how the immune system evolves with age and how vaccines work in older people has led to increasing focus on the development of vaccines aimed specifically at older age groups. We discuss strategies used to improve vaccine immunogenicity for older adults, focusing on licensed adjuvants.

FINDINGS

With age-related immune decline (immunosenescence), older adults face increased vulnerability to infections and severe complications. Immunosenescence affects T-cell and B-cell populations and innate immunity, leading to reduced chemotaxis, cytotoxicity, and altered cytokine production. This contributes to inflammaging-low-grade, chronic inflammation linked to aging. However, immune responses vary due to genetics and life-long exposures, making chronological age an imperfect indicator of immune health. Vaccination remains key to prevention, yet immune dysfunction complicates vaccine efficacy. Strategies to enhance responses in older adults include mRNA vaccines, high-antigen content vaccines, intradermal administration, and adjuvants. mRNA COVID-19 vaccines generated strong immune responses in older adults, though lower than in younger groups. High-antigen content influenza vaccines have shown superior efficacy compared to standard vaccination. Adjuvants offer a well-established approach to boosting vaccine responses by enhancing innate immunity.

CONCLUSIONS

Of various strategies used to improve immunogenicity of vaccines for older adults, adjuvants have been the most consistently effective and practical. More recently, mRNA vaccines have also shown great promise.

Trained immunity enhances host resistance to infection in aged mice

Aging significantly increases the incidence and severity of infections, with individuals aged 65 and above accounting for 65% of sepsis cases. Innate immune training, known as "trained immunity" or "innate immune memory," has emerged as a potential strategy to enhance infection resistance by modulating the aging immune system. We investigated the impact of -glucan-induced trained immunity on aged mice (18 to 20 mo old) compared with young adult mice (10 to 12 wk old). Our findings showed that β-glucan equally augmented the host resistance to infection in both young and aged mice. This enhancement was characterized by augmented bacterial clearance, enhanced leukocyte β, and decreased cytokine production in response to Pseudomonas aeruginosa infection. Furthermore, young and aged trained macrophages displayed heightened metabolic capacity and improved antimicrobial functions, including enhanced phagocytosis and respiratory burst. RNA-seq analysis showed a distinctive gene expression pattern induced by trained immunity in macrophages characterized by activation of pathways regulating inflammation and the host response to infection and suppression of pathways regulating cell division, which was consistently observed in both young and aged groups. As compared with macrophages from young mice, aged macrophages showed increased activation of gene ontology pathways regulating angiogenesis, connective tissue deposition, and wound healing. Our results indicate that immune training can be effectively induced in aging mice, providing valuable insights into potential strategies for enhancing infection resistance in the elderly.

Old hematopoietic stem cells retain competence to reconstitute a youthful B cell system that is highly responsive to protein-based vaccination

BACKGROUND

Ageing-associated remodeling of the murine B cell system is accompanied with a reduction of CD19+ B cells such as follicular B cells (FOB) and an accumulation of age-associated B cells (ABC) or activated B cell subsets. This remodeling is thought to confer an attenuated antibody response, such as to SARS-CoV-2 spike (S) vaccines in both aged mice and humans. To gain insight into the de novo development and function of an old B cell system, we reconstituted young and old immune systems by transferring hematopoietic stem cells (HSCs) from immune-competent young (2-3 months) CD45.1+ donors (DY-HSC) or old (20-24 months) donors (DO-HSC) into T and B cell-deficient young recipient CD45.2+ RAG1-/- mice, followed by protein-based vaccination.

RESULTS

In the same environment of young RAG1-/- mice, transplanted DO-HSCs compared to DY-HSCs reconstituted lower numbers of CD19+ B cells and CD45.1+ cells, though the engraftment of donor-derived HSCs in the young bone marrow (BM) was very similar. Furthermore, indicative for youthful and unchallenged B cell systems, and in contrast to aged mice, very low levels of antigen-experienced memory B cells or age-associated B cells (ABC) developed in both DY-HSC and DO-HSC hosts. The commercially available recombinant SARS-CoV-2 S vaccine (NVX-CoV2373) induced lower IgG+ S-antibody titers and pseudovirus neutralization activity in old compared to young mice. In contrast, very similar high IgG+ S-antibody titers were induced in DO-HSC and DY-HSC hosts, and pseudovirus neutralization activity was even enhanced in DO-HSC compared with DY-HSC hosts.

CONCLUSIONS

Both DO-HSCs and DY-HSCs established in the young recipient BM to a similar extend, suggesting that the concomitant reduction in the de novo reconstitution of CD19+ B cells in DO-HSC vs. DY-HSC transplanted animals is specifically related to old HSCs. DO-HSCs and DY-HSCs reconstitute very similar unchallenged B cell systems that efficiently elicit antigen-specific IgG antibodies by protein-based vaccination. Old HSCs thus retain competence to reconstitute a youthful and functional B cell system, at least in the young environment of transplanted RAG1-/- mice. This suggests that it is primarily age-related factors, and not HSCs per se, that influence the composition and functionality of the old B cell system.

Durability of antibody titers and associated factors after the booster dose of COVID-19 mRNA vaccination in Japanese SARS-CoV-2 infection-naive residents in geriatric intermediate care facilities

AIM

Elderly adults are at higher risk for severe COVID-19 infection. This multicenter, prospective cohort study assessed immunogenicity after COVID-19 vaccinations in elderly residents compared with staff in geriatric intermediate care facilities. Predictors of lower antibody titers were also examined.

METHODS

Fifty-four residents and 117 staff who had received three doses of the COVID-19 mRNA vaccine between March 2021 and September 2022 were included. Anti-receptor binding domain antibody titers were measured 3-4 weeks and 6 months after the vaccinations. Adjusted geometric mean titers (GMT) were calculated using multivariable linear mixed effects models.

RESULTS

After the first dose, residents had a significantly lower adjusted GMT than did staff (115 vs. 267 AU/mL, P < 0.01), whereas the adjusted GMT of residents was comparable to that of staff after the third dose (14 178 vs. 12 159 AU/mL, P = 0.63). However, 6 months later, the adjusted GMT of residents was less than half that of staff (1645 vs. 4302 AU/mL, P < 0.01). In residents, steroid users had a significantly lower adjusted GMT than did steroid nonusers.

CONCLUSIONS

The third dose of mRNA vaccine boosted the immune response of elderly residents. However, their antibody titers, particularly in steroid users, were highly attenuated 6 months after the last vaccination. For this population, attention should be focused on additional vaccinations. Geriatr Gerontol Int 2025; 25: 588-597.

Characteristics of peripheral lymphocyte subsets and antibodies in COVID-19-infected kidney transplantation recipients

BACKGROUND

Peripheral lymphocyte subsets play vital roles in various disease conditions. However, the roles of kidney transplant recipients (KTRs) with novel coronavirus pneumonia (COVID-19) are still unclear. In this research, we investigated the predictive value of peripheral blood lymphocyte subsets on the severity of KTRs with COVID-19 and the correlation between antibodies and lymphocyte levels.

METHODS

84 patients with kidney transplantation combined with COVID-19 admitted from December 2022 to February 2023 were included. On the basis of the severity of COVID-19, they were categorized into a mild (n = 49) and a severe group (n = 35). The logistic regression method was utilized to build the critical risk prediction model for KTRs complicated with COVID-19. The receiver operator characteristic curve (ROC), calibration plot and clinical decision curve analysis (DCA) were applied to assess the discrimination, calibration and clinical application value of this model. The Spearman correlation test was applied to examine the connection between antibodies and various immune indexes.

RESULTS

Except for the increase of CD4+HLA-DR+ T cells, the number of CD3+, CD4+, and CD8+ T cell subsets in severe was lower than that in mild (P < 0.05). IL-6 in severe was higher than mild (P < 0.05). After screening variables, we established a regression equation prediction model, logit (P) = 4.965+ (-0.038) × (CD3+/lymphocytes (%)) + 0.064× (CD4+HLA-DR+/ CD4+ T cells (%)) + (-0.040) × (CD14+HLA-DR+/monocytes (%)). The area under the ROC curve (AUC) of the prediction model was 0.779 (95 % CI 0.679-0.879, P = 0.001). The cut-off value was 0.308, with a prediction sensitivity of 0.829 (95 % CI 0.657-0.928) and a specificity of 0.653 (95 % CI 0.503-0.779). Logistic regression analysis showed the increase in the percentage of CD4+HLA-DR+ T cells among CD4+ T cells was a risk factor for COVID-19 severity among kidney transplant recipients, while the increase in the percentage of CD3+ T cells among lymphocytes and CD14+HLA-DR+ monocytes among CD14+ monocytes acted as protective factors. COVID-19 antibodies were negatively correlated with CD8+CD45RA+CD27- (Terminally Differentiated Effector Memory T Cells, TEMRA), CD8+CD28-, CD8+CD38+ and CD4+CD38+ T cells, while positively correlated with CD8+CD45RA-CD27- (Effector Memory T cells, T8EM), CD8+CD45RA-CD27+ (Central Memory T cells, T8CM) and CD8+CD28+ T cells.

CONCLUSION

A predictive model was developed and validated for predicting the severe form of COVID-19 in KTRs. The model showed good predictive ability, concordance, and potential clinical utility.

Gender, Age and COVID-19 Vaccination Status in African American Adult Faith-Based Congregants in the Southeastern United States

OBJECTIVES

The COVID-19 pandemic has revealed significant differences in COVID-19 vaccination rates, with African Americans reporting lower rates compared to other racial and ethnic groups. The purpose of these analyses was to assess whether COVID-19 vaccination status differed according to age in a sample of 1,240 African American adult congregants of faith-based organizations ages 18 years or older, and to examine whether this association was moderated by gender.

DESIGN

We developed and administered a 75-item cross-sectional survey, the Triad Pastor's Network COVID-19 and COVID-19 Vaccination survey, to assess experiences and perceptions regarding the COVID-19 virus and vaccines. We assessed the association between age and having received > 1 dose of a COVID-19 vaccine using unadjusted and multivariable binary logistic regression models, and the interaction of age and gender with COVID-19 vaccination status in a multivariable model.

RESULTS

Approximately 86% of participants reported having received ≥ 1 dose of a COVID-19 vaccine. The mean age (standard deviation) of the sample was 51.33 (16.62) years, and 70.9% of the sample was comprised of women. The age by gender interaction term in the multivariable model was significant (p = 0.005), prompting additional analyses stratified by gender. In women, increased age was significantly associated with higher odds of COVID-19 vaccination (odds ratio = 1.09; 95% Confidence Interval 1.06, 1.11; p < 0.001). In men, the association was not significant (p = 0.44).

CONCLUSIONS

Older age was positively associated with COVID-19 vaccination in African American women, but not African American men, which may inform strategies to increase vaccination rates.

Longitudinal Analysis of Nursing Home Residents' T-Cell Responses After SARS-CoV-2 mRNA Vaccinations Shows Influence of Biological Sex and Infection History

BACKGROUND

Vaccines and vaccine boosting have blunted excess morbidity and mortality from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in older nursing home residents (NHR). However, the impact of repeated vaccination on the T-cell response based on biological sex and prior infection of NHR remain understudied.

METHODS

We examined T-cell responses to SARS-CoV-2 mRNA vaccines in a cohort of NHR and healthcare workers (HCW) over 2 years. We used interferon-γ ELIspot and flow cytometry to assess T-cell response before, 2 weeks, and 6 months after the initial series and each of 2 booster vaccines. We analyzed these data longitudinally with mixed-effect modeling and also examined subsets of our cohorts for additional changes in T-cell effector function.

RESULTS

Prior SARS-CoV-2 infection and female sex contributed to higher T-cell response in NHR but not HCW. When looking across time points, NHR but not HCW with prior infection had significantly higher T-cell responses than infection-naive subjects. These patterns of response were maintained across multiple booster vaccinations.

CONCLUSIONS

These results suggest that the age, multimorbidity, and/or frailty of the NHR cohort may accentuate sex and infection status differences in T-cell response to mRNA vaccination.

Immunogenicity of BNT162b2 as a first booster after a ChAdOx1 primary series in a Thai geriatric population living with frailty

OBJECTIVES

Impact of frailty towards immunogenicity and reactogenicity of BNT162b2 boosters administered via intramuscular or intradermal routes in a Thai geriatric population DESIGN: Prospective, randomized, open-labeled.

SETTING

Siriraj Hospital, Thailand.

PARTICIPANTS

Geriatric adults aged ≥65 years.

INTERVENTION

10 μg intradermal or 30 μg intramuscular BNT162b2 (Pfizer-BioNTech).

MEASUREMENTS

Anti-SARS-CoV-2 receptor binding domain IgG, neutralizing antibodies (NAb), and interferon-gamma producing cells against Wuhan and Omicron BA.4/5. Analyses were stratified based on participants' Clinical Frailty Scale.

RESULTS

A total of 139 participants were included in the analysis. Two-four weeks post-booster administration, NAb titers against Wuhan but not Omicron BA.4/5 were significantly lower among frail participants than non-frail participants who received intramuscular administration. Spike-specific T cell responses were similar for frail and non-frail participants, regardless of administration route. Frail participants who received intradermal BNT162b2 had fewer local adverse events (AEs), but higher systemic AEs than non-frail participants.

CONCLUSION

Similar immune responses across vaccine routes warrants further evaluation of intradermal BNT162b2 in frail geriatric populations. Frail participants may be more sensitive to reporting systemic AEs.

REGISTRATION OF CLINICAL TRIALS

The parent study was registered under the Thai Clinical Trials Registry (TCTR20220112002).

Immune response kinetics to SARS-CoV-2 infection and COVID-19 vaccination among nursing home residents-Georgia, October 2020-July 2022

BACKGROUND

Understanding the immune response kinetics to SARS-CoV-2 infection and COVID-19 vaccination is important in nursing home (NH) residents, a high-risk population.

METHODS

An observational longitudinal evaluation of 37 consenting vaccinated NH residents with/without SARS-CoV-2 infection from October 2020 to July 2022 was conducted to characterize the immune response to spike protein due to infection and/or mRNA COVID-19 vaccine. Antibodies (IgG) to SARS-CoV-2 full-length spike, nucleocapsid, and receptor binding domain protein antigens were measured, and surrogate virus neutralization capacity was assessed using Meso Scale Discovery immunoassays. The participant's spike exposure status varied depending on the acquisition of infection or receipt of a vaccine dose. Longitudinal linear mixed effects modeling was used to describe trajectories based on the participant's last infection or vaccination; the primary series mRNA COVID-19 vaccine was considered two spike exposures. Mean antibody titer values from participants who developed an infection post receipt of mRNA COVID-19 vaccine were compared with those who did not. In a subset of participants (n = 15), memory B cell (MBC) S-specific IgG (%S IgG) responses were assessed using an ELISPOT assay.

RESULTS

The median age of the 37 participants at enrollment was 70.5 years; 30 (81%) had prior SARS-CoV-2 infection, and 76% received Pfizer-BioNTech and 24% Moderna homologous vaccines. After an observed augmented effect with each spike exposure, a decline in the immune response, including %S IgG MBCs, was observed over time; the percent decline decreased with increasing spike exposures. Participants who developed an infection at least two weeks post-receipt of a vaccine were observed to have lower humoral antibody levels than those who did not develop an infection post-receipt.

CONCLUSIONS

These findings suggest that understanding the durability of immune responses in this vulnerable NH population can help inform public health policy regarding the timing of booster vaccinations as new variants display immune escape.

Elevated CD4+ T Cell Senescence Associates with Impaired Immune Responsiveness in Severe COVID-19

Aging is a critical risk factor for unfavorable clinical outcomes among COVID-19 patients and may impact vaccine efficacy. However, whether the senescence of T cells is associated with severe COVID-19 outcome in elderly individuals is unclear. Using flow cytometry, we analyzed the frequency of senescent T cells (Tsens) in peripheral blood from 100 hospitalized elderly COVID-19 patients and compared differences between those with mild/moderate and severe/critical illness. We also assessed correlations between the percentage of Tsens and the quantity and quality of spike-specific antibodies by ELISA, neutralizing antibody test kit, and ELISPOT assay respectively, the cytokine production profile of COVID-19 reactive T cells, and plasma soluble factors by cytometric bead array (CBA). Our study found a significantly elevated level of CD4+ Tsens in patients with severe/critical disease compared to those with mild/moderate illness. Patients with a higher level of CD4+ Tsens (>19.78%) showed a decreased survival rate compared to those with a lower level (≤19.78%). This is more pronounced among patients with breakthrough infections. The percentage of CD4+ Tsens was negatively correlated with spike-specific antibody titers, neutralization ability, and COVID-19 reactive IL-2+CD4+ T cells. In addition, spike-specific antibody levels were positively correlated with IL-2 producing T cells and plasma IL-2 amount. Mechanistically, with defective CD40L, T cells from patients with CD4+ Tsens >19.78% were unable to support B cell proliferation and differentiation. Our data demonstrate that the percentage of CD4+ Tsens in peripheral blood may serve as a reliable biomarker for the prognosis of severe COVID-19 patients, especially in breakthrough infections. Therefore, restoring the immune response of CD4+ Tsens may be key to preventing severe illness and improving vaccine efficacy in older adults.

Data resource profile: COVid VAXines effects on the aged (COVVAXAGE)

Background

To improve the assessment of COVID-19 vaccine use, safety, and effectiveness in older adults and persons with complex multimorbidity, the COVid VAXines Effects on the Aged (COVVAXAGE) database was established by linking CVS Health and Walgreens pharmacy customers to Medicare claims.

Methods

We deterministically linked CVS Health and Walgreens customers who had a pharmacy dispensation/encounter paid for by Medicare to Medicare enrollment and claims records. Linked data include U.S. Medicare claims, Medicare enrollment files, and community pharmacy records. The data currently span 01/01/2016 to 08/31/2022. "Research-ready" files were created, with weekly indicators for vaccinations, censoring, death, enrollment, demographics, and comorbidities. Data are updated quarterly.

Results

As of November 2022, records for 27,086,723 CVS Health and 23,510,025 Walgreens unique customer IDs were identified for potential linkage. Approximately 91% of customers were matched to a Medicare beneficiary ID (95% for those aged 65 years or older). In the final linked cohort, there were 38,250,873 unique beneficiaries representing ~60% of the Medicare population. Among those alive and enrolled in Medicare as of January 1, 2020 (n = 33,721,568; average age = 73 years, 74% White, 51% Medicare Fee-for-Service, and 11% dual-eligible for Medicaid), the average follow-up time was 130 weeks. The cohort contains 16,021,055 beneficiaries with evidence a first COVID-19 vaccine dose. Data are stored on the secure Medicare & Medicaid Resource Information Center Health & Aging Data Enclave.

Data access

Investigators with funded or in-progress funding applications to the National Institute on Aging who are interested in learning more about the database should contact Dr Vincent Mor [Vincent_mor@brown.edu] and Dr Kaleen Hayes [kaley_hayes@brown.edu]. A data dictionary can be provided under reasonable request.

Conclusions

The COVVAXAGE cohort is a large and diverse cohort that can be used for the ongoing evaluation of COVID-19 vaccine use and other research questions relevant to the Medicare population.

COVID-19 Adenoviral Vector Vaccination Elicits a Robust Memory B Cell Response with the Capacity to Recognize Omicron BA.2 and BA.5 Variants

Following the COVID-19 pandemic, novel vaccines have successfully reduced severe disease and death. Despite eliciting lower antibody responses, adenoviral vector vaccines are nearly as effective as mRNA vaccines. Therefore, protection against severe disease may be mediated by immune memory cells. We here evaluated plasma antibody and memory B cells (Bmem) targeting the SARS-CoV-2 Spike receptor-binding domain (RBD) elicited by the adenoviral vector vaccine ChAdOx1 (AstraZeneca), their capacity to bind Omicron subvariants, and compared this to the response to mRNA BNT162b2 (Pfizer-BioNTech) vaccination. Whole blood was sampled from 31 healthy adults pre-vaccination and 4 weeks after dose one and dose two of ChAdOx1. Neutralizing antibodies (NAb) against SARS-CoV-2 were quantified at each time point. Recombinant RBDs of the Wuhan-Hu-1 (WH1), Delta, BA.2, and BA.5 variants were produced for ELISA-based quantification of plasma IgG and incorporated separately into fluorescent tetramers for flow cytometric identification of RBD-specific Bmem. NAb and RBD-specific IgG levels were over eight times lower following ChAdOx1 vaccination than BNT162b2. In ChAdOx1-vaccinated individuals, median plasma IgG recognition of BA.2 and BA.5 as a proportion of WH1-specific IgG was 26% and 17%, respectively. All donors generated resting RBD-specific Bmem, which were boosted after the second dose of ChAdOx1 and were similar in number to those produced by BNT162b2. The second dose of ChAdOx1 boosted Bmem that recognized VoC, and 37% and 39% of WH1-specific Bmem recognized BA.2 and BA.5, respectively. These data uncover mechanisms by which ChAdOx1 elicits immune memory to confer effective protection against severe COVID-19.

Heterologous DNA-prime/protein-boost immunization with a monomeric SARS-CoV-2 spike antigen redundantizes the trimeric receptor-binding domain structure to induce neutralizing antibodies in old mice

A multitude of alterations in the old immune system impair its functional integrity. Closely related, older individuals show, for example, a reduced responsiveness to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines. However, systematic strategies to specifically improve the efficacy of vaccines in the old are missing or limited to simple approaches like increasing the antigen concentration or injection frequencies. We here asked whether the intrinsic, trimeric structure of the SARS-CoV-2 spike (S) antigen and/or a DNA- or protein-based antigen delivery platform affects priming of functional antibody responses particularly in old mice. The used S-antigens were primarily defined by the presence/absence of the membrane-anchoring TM domain and the closely interlinked formation/non-formation of a trimeric structure of the receptor binding domain (S-RBD). Among others, we generated vectors expressing prefusion-stabilized, cell-associated (TM+) trimeric "S2-P" or secreted (TM-) monomeric "S6-PΔTM" antigens. These proteins were produced from vector-transfected HEK-293T cells under mild conditions by Strep-tag purification, revealing that cell-associated but not secreted S proteins tightly bound Hsp73 and Grp78 chaperones. We showed that both, TM-deficient S6-PΔTM and full-length S2-P antigens elicited very similar S-RBD-specific antibody titers and pseudovirus neutralization activities in young (2-3 months) mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. The trimeric S2-P antigen induced high S-RBD-specific antibody responses in old (23-24 months) mice through DNA-prime/DNA-boost vaccination. Unexpectedly, the monomeric S6-PΔTM antigen induced very low S-RBD-specific antibody titers in old mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. However, old mice efficiently elicited an S-RBD-specific antibody response after heterologous DNA-prime/protein-boost immunization with the S6-PΔTM antigen, and antibody titers even reached similar levels and neutralizing activities as in young mice and also cross-reacted with different S-variants of concern. The old immune system thus distinguished between trimeric and monomeric S protein conformations: it remained antigen responsive to the trimeric S2-P antigen, and a simple change in the vaccine delivery regimen was sufficient to unleash its reactivity to the monomeric S6-PΔTM antigen. This clearly shows that both the antigen structure and the delivery platform are crucial to efficiently prime humoral immune responses in old mice and might be relevant for designing "age-adapted" vaccine strategies.

Antibody response in elderly vaccinated four times with an mRNA anti-COVID-19 vaccine

The humoral response after the fourth dose of a mRNA vaccine against COVID-19 has not been adequately described in elderly recipients, particularly those not exposed previously to SARS-CoV-2. Serum anti-RBD IgG levels (Abbott SARS-CoV-2 IgG II Quant assay) and neutralizing capacities (spike SARS-CoV-2 pseudovirus Wuhan and Omicron BA.1 variant) were measured after the third and fourth doses of a COVID-19 mRNA vaccine among 46 elderly residents (median age 85 years [IQR 81; 89]) of an assisted living facility. Among participants never infected by SARS-CoV-2, the mean serum IgG levels against RBD (2025 BAU/ml), 99 days after the fourth vaccine, was as high as 76 days after the third vaccine (1987 BAU/ml), and significantly higher (p = 0.030) when the latter were corrected for elapsed time. Neutralizing antibody levels against the historical Wuhan strain were significantly higher (Mean 1046 vs 1573; p = 0.002) and broader (against Omicron) (Mean 170 vs 375; p = 0.018), following the fourth vaccine. The six individuals with an Omicron breakthrough infection mounted strong immune responses for anti-RBD and neutralizing antibodies against the Omicron variant indicating that the fourth vaccine dose did not prevent a specific adaptation of the immune response. These findings point out the value of continued vaccine boosting in the elderly population.

Kinetics of COVID-19 mRNA primary and booster vaccine-associated neutralizing activity against SARS-CoV-2 variants of concern in long-term care facility residents: a prospective longitudinal study in Japan

BACKGROUND

Coronavirus disease 2019 (COVID-19) remains a threat to vulnerable populations such as long-term care facility (LTCF) residents, who are often older, severely frail, and have multiple comorbidities. Although associations have been investigated between COVID-19 mRNA vaccine immunogenicity, durability, and response to booster vaccination and chronological age, data on the association of clinical factors such as performance status, nutritional status, and underlying comorbidities other than chronological age are limited. Here, we evaluated the anti-spike IgG level and neutralizing activity against the wild-type virus and Delta and Omicron variants in the sera of LTCF residents, outpatients, and healthcare workers before the primary vaccination; at 8, 12, and 24 weeks after the primary vaccination; and approximately 3 months after the booster vaccination. This 48-week prospective longitudinal study was registered in the UMIN Clinical Trials Registry (Trial ID: UMIN000043558).

RESULTS

Of 114 infection-naïve participants (64 LTCF residents, 29 outpatients, and 21 healthcare workers), LTCF residents had substantially lower anti-spike IgG levels and neutralizing activity against the wild-type virus and Delta variant than outpatients and healthcare workers over 24 weeks after the primary vaccination. In LTCF residents, booster vaccination elicited neutralizing activity against the wild-type virus and Delta variant comparable to that in outpatients, whereas neutralizing activity against the Omicron variant was comparable to that in outpatients and healthcare workers. Multiple regression analyses showed that age was negatively correlated with anti-spike IgG levels and neutralizing activity against the wild-type virus and Delta variant after the primary vaccination. However, multivariate regression analysis revealed that poor performance status and hypoalbuminemia were more strongly associated with a lower humoral immune response than age, number of comorbidities, or sex after primary vaccination. Booster vaccination counteracted the negative effects of poor performance status and hypoalbuminemia on the humoral immune response.

CONCLUSIONS

LTCF residents exhibited suboptimal immune responses following primary vaccination. Although older age is significantly associated with a lower humoral immune response, poor performance status and hypoalbuminemia are more strongly associated with a lower humoral immune response after primary vaccination. Thus, booster vaccination is beneficial for older adults, especially those with a poor performance status and hypoalbuminemia.

SARS-CoV-2 rapid antibody test results and subsequent risk of hospitalisation and death in 361,801 people

The value of SARS-CoV-2 lateral flow immunoassay (LFIA) tests for estimating individual disease risk is unclear. The REACT-2 study in England, UK, obtained self-administered SARS-CoV-2 LFIA test results from 361,801 adults in January-May 2021. Here, we link to routine data on subsequent hospitalisation (to September 2021), and death (to December 2021). Among those who had received one or more vaccines, a negative LFIA is associated with increased risk of hospitalisation with COVID-19 (HR: 2.73 [95% confidence interval: 1.15,6.48]), death (all-cause) (HR: 1.59, 95% CI:1.07, 2.37), and death with COVID-19 as underlying cause (20.6 [1.83,232]). For people designated at high risk from COVID-19, who had received one or more vaccines, there is an additional risk of all-cause mortality of 1.9 per 1000 for those testing antibody negative compared to positive. However, the LFIA does not provide substantial predictive information over and above that which is available from detailed sociodemographic and health-related variables. Nonetheless, this simple test provides a marker which could be a valuable addition to understanding population and individual-level risk.