Evaluating Johnson and Johnson COVID-19 Vaccination Outcomes in a Low-Income Hispanic Population

The study addresses the need to understand real-world immune responses to the single-dose Johnson & Johnson (J&J; Ad26.COV2.S) COVID-19 vaccine in a low-income Hispanic population, a group disproportionately affected by COVID-19 infections and mortality and underrepresented in prior vaccine studies. With global vaccination reducing severe outcomes but immunity waning over months and viral variants eroding neutralization, there is a need for practical, low-cost tools to monitor immunity in primary care, especially in vulnerable communities. The research question is whether a single J&J dose elicits a detectable humoral (antibody) response in infection-naïve, low-income Hispanic patients and how durable that response is over approximately 6 months, along with identifying demographic and clinical correlates of seropositivity. The study’s purpose is to inform clinical and policy strategies to better serve high-risk minority populations.

Background highlights include: (1) J&J vaccine received EUA on 29 March 2021 and has shown effectiveness against infection and hospitalization in large observational studies, though effectiveness wanes over 4–6 months; boosters raise antibody levels substantially. (2) Lateral flow assays (LFAs) can differentiate antibodies to spike (S) vs nucleocapsid (N), helping distinguish vaccine-induced from infection-induced antibodies in spike-based vaccine recipients. (3) The CLUNGENE SARS-CoV-2 IgG/IgM rapid test targets RBD from spike and nucleocapsid and has reported sensitivity 87% and specificity 98%. (4) Literature documents variable vaccine effectiveness across time and variants, with waning neutralization, and suggests T-cell memory may remain relatively robust. (5) Hispanic populations have experienced higher infection and death rates, potentially due to socioeconomic and occupational exposures; yet they are underrepresented in vaccine-effectiveness studies. This context motivates assessing vaccine response and durability using point-of-care serology in a low-income Hispanic cohort.

Design: Prospective, longitudinal observational study under Western IRB approval (Sponsor: Alivio Medical Center, IRB Pr #20210840). Setting and population: Alivio Medical Center, a free-standing point-of-care clinic serving a low-income Hispanic community in Indianapolis, IN. Participants: Adults seeking J&J vaccination between 8 June 2021 and 25 October 2021. Inclusion criteria included no history suggestive of COVID-19 and negative baseline SARS-CoV-2 antibody test; those with positive baseline antibodies were excluded. All staff were Spanish-fluent; demographic, clinical, and socioeconomic data were collected via EMR (iSalus) and interviews. Procedures: After standard screening for prior infection, eligible consenting patients received the single J&J dose. Antibody testing was performed using the CLUNGENE SARS-CoV-2 IgM/IgG LFA at multiple time points: initial post-vaccination window (7–64 days), and subsequent follow-ups around 90 days and later; patients were asked to return twice over ~120 days. Follow-up visits were categorized as <30, 30–60, 60–90, 90–120, and >120 days post-vaccination. The LFA provides qualitative IgM/IgG results in ~15 minutes; a test was positive if either IgM or IgG was present. Data and analysis: EMR data captured comorbidities (e.g., diabetes, hypertension, hyperlipidemia, rheumatologic disease), medications, and symptoms/adverse events. Pearson correlations were computed between antibody positivity (binary) and variables (e.g., sex, age, comorbidities, height, weight, symptoms, days since vaccination). Correlations with absolute value ≥0.3 were considered moderate and ≥0.5 strong.

Cohort and follow-up: 74 patients were invited; 53 qualified (baseline antibody negative); 39 unique patients returned for at least one follow-up visit (total 60 follow-up visits). Antibody positivity overall: Among the 39 returning patients, 16 (41%) had negative antibodies in one or more follow-up appointments; 5 (12%) were negative at both visits, 10 (26%) attended only one follow-up and were negative, and 1 (3%) was negative then later positive. In total, 23 (59%) had at least one positive antibody result; 15 (38%) were positive at both visits and 8 (21%) attended only one follow-up and were positive. Positivity by time since vaccination (visit-level): <30 days: 11/15 (73%) positive; 30–60 days: 5/6 (83%) positive; 60–90 days: 6/9 (67%) positive; 90–120 days: 8/14 (57%) positive; >120 days: 9/16 (56%) positive. Temporal trend: Antibody positivity showed a declining association with time since vaccination—overall correlation with days after vaccination was −0.22, becoming more negative at later windows (e.g., −0.44 at 90–120 days; −0.37 at >120 days). Correlates (all follow-up visits): Positive antibody result correlated with female sex (r=0.15). Negative correlations were observed with male sex (−0.15), age (−0.12), prior COVID-19 infection (−0.18), height (−0.14), weight (−0.13), fatigue (−0.23), and days after vaccination (−0.22). Subgroup highlights: <30 days (N=15): notable negative correlations with fatigue (−0.85), weight (−0.55), hypertension (−0.45), age (−0.40); positive with female sex (0.34), days since vaccination (0.21). 30–60 days (N=6): strong negative with fatigue (−1.00); negative with days (−0.31); positive with male sex (0.45), pain at injection site (0.32). 60–90 days (N=9): negative with rheumatologic diseases (−0.50) and pain at injection site (−0.50); negative with days (−0.23); positive with fatigue (0.38). 90–120 days (N=14): negative with days (−0.44), male sex (−0.29), age (−0.24), height (−0.32), weight (−0.27); positive with diabetes (0.24), hyperlipidemia (0.24). >120 days (N=16): negative with days (−0.33), prior infection (−0.29), pain at injection site (−0.29); modest positive with hypertension (0.10). Overall, results indicate detectable antibody responses in a majority at some time point, with waning association over time and varied correlations with demographics/comorbidities.

The authors interpret their data as indicating a low detectable humoral response to a single J&J dose in this low-income Hispanic population and potential vulnerability to COVID-19, noting that only a small proportion of subjects showed persistent antibody positivity by their assessment. They contextualize these findings with mixed evidence from larger studies on safety and effectiveness by ethnicity, emphasizing the underrepresentation of Hispanic populations in trials and the importance of socioeconomic and occupational factors (e.g., essential work, limited ability to work from home) that increase exposure risk. They note that a single-dose regimen is attractive for a mobile workforce, yet in their cohort a substantial fraction lacked detectable antibodies 30–120 days post-vaccination, suggesting potential for reinfection risk and highlighting disparities. Despite individual variability in immune response, they observed a median protective effect of over 5 months consistent with prior studies, while acknowledging that neutralizing antibodies decline over time and memory responses are harder to quantify. They advocate for simple, low-cost, point-of-care serology as an adjunct for clinicians to monitor vaccine response durability in vulnerable communities.

In a working-class, low-income Hispanic population served by an urban clinic, the single-dose J&J vaccine showed limited detectable humoral responses over time, with evidence of waning positivity and associations with patient factors. Socioeconomic conditions likely exacerbate vulnerability to COVID-19, and comorbidities such as diabetes, hypertension, hyperlipidemia, and rheumatologic diseases may influence vaccine response. Point-of-care, spike-targeted lateral flow antibody tests can provide practical monitoring to guide clinical decision-making in community settings. The study underscores the need for more research focused on low-income minority populations to optimize prevention and care strategies. The research received no external funding.

Key limitations include the small, heterogeneous convenience sample; limited follow-up with only 39 of 53 eligible participants returning; potential scheduling and work-related barriers affecting participation; and the lack of functional immune assays (neutralizing antibody titers, B-cell memory, T-cell responses). The small subgroup sample sizes make correlation estimates unstable (e.g., some time windows had N≤9), increasing susceptibility to random variation and limiting generalizability.