Land Border Travelers in Ghana Show Sky-High COVID-19 Antibody Levels

When Ghana sealed its air and land borders in the early phase of the COVID-19 pandemic, the move was intended to slow the importation of SARS-CoV-2 into the country. By the time the borders were being prepared for reopening under regulated conditions, public health officials faced a critical question: how much immunity to the virus already existed among the people crossing back and forth over land boundaries? A new cross-sectional study, published in BMC Infectious Diseases, provides one of the most detailed answers to date for West Africa, reporting that more than nine in ten travelers entering Ghana through its major land borders carried detectable neutralizing antibodies against SARS-CoV-2 in 2022.

The research team, led by investigators at the Noguchi Memorial Institute for Medical Research at the University of Ghana together with the Ghana Field Epidemiology and Laboratory Training Programme, recruited travelers aged 18 years and above who entered the country through one of ten major land borders between February and July 2022. Participants were enrolled consecutively after providing written informed consent, in accordance with ethical approvals from the NMIMR Institutional Review Board and the Ghana Health Service Ethical Review Committee. During enrollment, each participant completed a semi-structured questionnaire capturing demographic characteristics, vaccination status, recent travel history, and any symptoms suggestive of COVID-19. Blood samples were then collected and shipped to laboratories associated with the Noguchi Memorial Institute and the Infectious Diseases Epidemiology Laboratory for serological analysis.

The laboratory centerpiece of the study was the WANTAI enzyme-linked immunosorbent assay, a commercial ELISA designed to detect antibodies that block the interaction between the viral spike protein and the human ACE2 receptor. This assay targets the spike-receptor binding domain, the region of the SARS-CoV-2 spike glycoprotein that the virus uses to latch onto host cells. Antibodies that bind this domain and prevent receptor engagement are known as neutralizing antibodies, and their presence in serum is widely regarded as a functional correlate of protection against infection. Unlike assays that detect antibodies against the nucleocapsid protein, which distinguish natural infection from vaccination, a spike-RBD neutralizing assay captures immunity induced by both vaccination and prior infection, making it well suited to estimating the total immune experience of a mobile population such as cross-border travelers.

The headline finding was striking. Overall seroprevalence of SARS-CoV-2 neutralizing antibodies among the sampled travelers stood at 92.3 percent, with a 95 percent confidence interval of 91.4 to 93.0 percent. In other words, nearly every traveler screened had immunological evidence of exposure to the virus or of vaccination against it. Seroprevalence was marginally higher before the formal reopening of the land borders, at 95.7 percent (95 percent CI: 94.2 to 97.1), than after reopening, when it measured 91.6 percent (95 percent CI: 91.0 to 92.5). The authors interpret this pattern as evidence that by early to mid-2022, transmission of SARS-CoV-2 in Ghana and neighboring countries had already been so widespread that the closed land borders were no longer holding back a susceptible population; immunity was essentially saturated on both sides of the boundary.

To move beyond raw percentages, the investigators fitted separate logistic regression models for the pre-border-opening and post-border-opening periods. Logistic regression is a statistical technique that models the probability of a binary outcome, in this case seropositivity, as a function of explanatory variables such as border of entry and vaccination status, yielding adjusted odds ratios that quantify the independent contribution of each factor. Because the study tested many coefficients simultaneously, the team applied the Benjamini-Hochberg procedure to control the false discovery rate across all non-reference adjusted coefficient tests within each model. This multiple-testing correction converts conventional p-values into q-values, protecting against spurious associations that inevitably arise when dozens of comparisons are made on a single dataset. Only associations surviving this correction, with q values below 0.05, were treated as statistically robust.

The geography of immunity emerged as a meaningful variable. After false discovery rate correction, travelers entering through the Oseikojokrom and Akanu borders had significantly lower odds of seropositivity before reopening compared with those entering through Aflao, one of Ghana’s busiest eastern border crossings. After reopening, the set of borders with lower odds relative to Aflao expanded to include Oseikojokrom, Akanu, Elubo, Paga, and Sampa. These differences likely reflect heterogeneity in local transmission intensity, vaccination coverage, and the volume and composition of cross-border traffic at each point of entry. Aflao, situated on the densely trafficked frontier with Togo, appears to have functioned as an immunological high-water mark against which the quieter western and northern crossings could be compared.

Vaccination status proved to be a consistent and powerful predictor across both time periods. Before the borders reopened, vaccinated travelers had 2.5 times higher odds of testing positive for neutralizing antibodies than unvaccinated travelers, with an adjusted odds ratio of 2.5 (95 percent CI: 1.7 to 3.5, q less than 0.001). After reopening, the association persisted though it attenuated somewhat, with vaccinated individuals showing 1.8 times higher odds of seropositivity (aOR = 1.8, 95 percent CI: 1.3 to 2.6, q = 0.005). The attenuation is plausibly explained by the growing contribution of natural infection to population immunity as the Omicron era progressed, which would have raised seropositivity among the unvaccinated and thereby narrowed the gap attributable to vaccination alone.

For the authors, the central policy implication is one of reassurance rather than alarm. The persistently high seroprevalence observed both before and after border reopening suggests that Ghana posed little to no risk of cross-border transmission of SARS-CoV-2 during the study window. Indeed, the pre-opening assessment provided empirical evidence that informed recommendations to reopen the land borders, a decision with substantial economic weight given the role of overland trade in the region and the ambitions of the African Continental Free Trade Area, which depends on the free movement of goods and people across these very crossings. Prolonged border closures carry costs of their own, from disrupted livelihoods to stalled commerce, and serosurveillance offers a way to weigh those costs against a realistic estimate of epidemiological risk.

The study also underscores the value of points of entry as natural surveillance platforms. Land borders are notoriously difficult settings for infectious disease monitoring, since travelers move in high volumes and formal health screening captures only symptomatic individuals. By embedding serological sampling directly into the border environment, with support from the Ghana Immigration Service and staff at the points of entry, the research team converted a routine administrative boundary into a population-level immunological observatory. The approach could be adapted for future pathogens, providing early warning of shifting immunity landscapes and helping authorities calibrate travel restrictions that are proportionate to actual risk rather than precautionary defaults.

Caveats remain, as they do in any cross-sectional serosurvey. Because the WANTAI ELISA detects binding to the spike-receptor binding domain, it cannot by itself disentangle antibodies generated by vaccination from those generated by infection, and a positive result indicates prior immune stimulation rather than current protection against emerging variants. The sampling of travelers also means the findings speak most directly to mobile, border-crossing populations, which may differ from the general population in age, vaccination uptake, and exposure history. Nevertheless, the sheer magnitude of the seroprevalence figures, consistently above 90 percent across both periods, leaves little ambiguity about the broader picture. By 2022, the virus had left its immunological signature across virtually the entire traveling population of Ghana’s land frontiers, and the borders could be reopened with confidence that they were not gateways for a naive population’s first encounter with SARS-CoV-2. The work, funded through the Global Fund’s COVID-19 Response Mechanism via the National AIDS Control Programme of the Ghana Health Service, stands as a template for evidence-based border policy in future epidemic emergencies.

Subject of Research: Seroprevalence of SARS-CoV-2 neutralizing antibodies among travelers entering Ghana through major land borders before and after border reopening in 2022

Article Title: Seroprevalence of SARS-CoV-2 neutralizing antibodies among travelers entering Ghana through major land borders, pre- and post-opening of borders, 2022

Article References: Donkor, I. O., Lomotey, E. S., Odumang, D. A., Mohammed, A. G., Asante, I. A., Kploanyi, E. E., Noora, C. L., Addo-Lartey, A., Affram, Y., Frimpong, J. A., Odikro, M. A., & Kenu, E. (2026). Seroprevalence of SARS-CoV-2 neutralizing antibodies among travelers entering Ghana through major land borders, pre- and post-opening of borders, 2022. BMC Infectious Diseases. https://doi.org/10.1186/s12879-026-14483-0

Image Credits: AI Generated

DOI: 10.1186/s12879-026-14483-0

Keywords: SARS-CoV-2, seroprevalence, neutralizing antibodies, Ghana, land borders, WANTAI ELISA, COVID-19 vaccination, border surveillance, logistic regression, false discovery rate, public health, BMC Infectious Diseases