A seroprevalence study of SARS-CoV-2 and seasonal coronaviruses after the first SARS-CoV-2 circulation in New Caledonia, Pacific region

Objectives

This study aimed to determine the seroprevalence of immunoglobulin G antibodies targeting SARS-CoV-2 and other human coronaviruses after the first circulation of SARS-CoV-2 in New Caledonia, Pacific region.

Methods

Blood samples were collected to detect the presence of SARS-CoV-2 immunoglobulin G antibodies. The sampling took place between July 2021 and July 2022 but was interrupted after the first circulation of SARS-CoV-2 (September 2021-March 2022) in New Caledonia. Data on ethnicity, age, gender, main residence, and anteriority of COVID-19 and vaccination were collected and analyzed.

Results

A total of 747 participants, representative of New Caledonia's adult population, were included in the study. We found that 81% of the population had antibody responses to SARS-CoV-2 at the end of July 2022. The vaccination rate was 75%, whereas infections had affected 40% of the population. Individuals aged >45 years were significantly more vaccinated than those aged 18-44 years (80%, 95% confidence interval 74-84%). Oceanians were the most infected (50%, 95% confidence interval 42-57%).

Conclusion

In New Caledonia, we show a high immunity rate (81%) after the first waves of SARS-CoV-2 circulation and the vaccination campaign. The analyses showed spatial heterogeneities in the infection rate across the territory and revealed that Oceanians were the most infected. Our study also highlighted high exposure of New Caledonia's population to other human coronaviruses.