Robust immune response to COVID-19 vaccination in the island population of Greenland

Background In Greenland, the COVID-19 pandemic was characterised by a late onset of community transmission and a low impact on the healthcare system, hypothesised as being partly due to a high uptake of vaccinations. To underpin this description, we aimed to assess the SARS-CoV-2 immune response post-vaccination in a Greenlandic population. Methods In this observational cohort study, we included 430 adults in Greenland who had received a complete two-dose SARS-CoV-2 vaccination at enrolment. The total plasma SARS-CoV-2 spike glycoprotein Ig antibodies (S-Ab) induced by either the BNT162b2 or mRNA-1273 vaccine, was measured up to 11 months after the second vaccine dose. In addition, total salivary S-Abs were examined in 107 participants, and the T-cell response to the spike glycoprotein was assessed in 78 participants out of the entire study cohort. Results Here we demonstrate that two months after the second vaccine dose, 96% of participants have protective plasma S-Ab levels. By 11 months, 98% have protective levels, with prior SARS-CoV-2 infection particularly enhancing S-Ab levels by 37% (95% CI 25–51%). Among individuals aged 60 years and older, we observe a 21% (95% CI 7–33%) reduction in antibody response. Total salivary S-Ab levels are detectable in all participants and significantly correlate with plasma levels. Moreover, all participants exhibit a robust SARS-CoV-2-specific T-cell response 11 months post-primary vaccination. Conclusions Our findings show that Greenlanders exhibit a robust and lasting immune response, both humoral and cellular, comparable to other population groups up to at least 11 months after the second vaccine dose. These results corroborate the hypothesis that vaccines contributed to the mild impact of the COVID-19 pandemic in the Greenlandic population. Plain Language Summary Effective public health measures were crucial to protect Greenland’s vulnerable population against the COVID-19 pandemic. Vaccines were particularly important, although their effectiveness in Greenland’s unique and isolated population had not been explored. Our aim was to determine the COVID-19 vaccines’ immunological response as a measure of protection among Greenlanders. By measuring antibody levels and immune cell activity, we demonstrate that over nine out of ten Greenlanders remained well protected by COVID-19 vaccines up to 11 months after their second vaccine dose, although older adults were less well protected. Prior COVID-19 infection or a boost