Longitudinal serological response to SARS-CoV-2 among Rohingya refugees in cox’s bazar, Bangladesh: implications for pandemic preparedness in humanitarian settings

Background Rohingya Myanmar nationals are at high risk of contracting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) due to densely populated camp areas with inadequate water, sanitation, and hygiene (WASH) infrastructure, along with limited awareness of hygiene practices. This study aimed to characterize the longitudinal SARS-CoV-2 antibody dynamics among Rohingya refugees in Cox’s Bazar to inform vaccination strategies and public health preparedness in humanitarian settings. Method Reverse transcription polymerase chain reaction (RT-PCR)-confirmed SARS-CoV-2 positive cases and their household members were enrolled and followed at multiple time points to monitor the IgG antibody response against the SARS-CoV-2 receptor binding domain (RBD) of the spike (S) protein. Result A total of 194 primary SARS-CoV-2 RT-PCR–positive cases were enrolled at baseline, of whom 47% were symptomatic, with the highest burden observed among individuals aged 18–55 years. At enrollment, 56% of primary cases had detectable IgG antibodies (≥ 500 ng/mL). Seropositivity increased to 80%, 88%, and 93% at days 30, 180, and 360, respectively. Among unvaccinated participants, RBD-specific IgG titers peaked at one month and remained detectable up to 12 months following natural infection. Among household members, seropositivity increased from 57% at enrollment to 71% at the one-month follow-up. Among vaccinated primary cases, antibody titers peaked at 1–2 months after vaccination and declined markedly within 4–5 months. Conclusion This study demonstrates robust antibody responses following natural SARS-CoV-2 infection and a marked rise-but rapid decline-of vaccine-induced immunity among Rohingya refugees. The findings highlight the need for timely booster doses, strengthened vaccination coverage, and continued serological monitoring to maintain protective immunity in high-density humanitarian settings. These insights can support targeted public health interventions and pandemic preparedness strategies for displaced and vulnerable populations.