Population Immunity AgaiNst mosquitO-borne Diseases in Vanuatu

The Pacific region is facing several emerging and neglected diseases notably mosquito-borne diseases as malaria or arboviroses among which dengue, Ross River, chikungunya and Zika. These diseases are an important cause of illness and death in the Pacific and the occurrence of arboviruses has increased in the recent years. In humans, these mosquito-borne diseases often have very similar clinical presentations (an acute febrile syndrome often self-limiting). However, these infections can progress to severe and fatal prognosis.

Numerous arboviroses outbreaks and in particular dengue outbreaks have affected Vanuatu for decades. Except for DENV and Zika for which epidemiological and virological data are available for Vanuatu, the knowledge on chikungunya and Ross River circulation is very limited and needs to be defined as both viruses have intensively circulated in the region in the past. Knowledge of the level of immune protection of the population for these mosquito-borne diseases is incomplete. For this purpose, seroprevalence studies that intend to retrospectively look for antibodies (IgG) as an evidence of previous infections by a specific pathogen would be highly informative. Knowing the serological profile of the Vanuatu population for dengue and other arboviruses as Ross River, chikungunya and Zika that could have affected the country in the past would be useful in defining the population likely to be infected by future epidemics.

COVID-19 pandemic caused by SARS-CoV-2 as caused over 520 million cases since December 2019. Vanuatu has been relatively spared from the pandemic due to the establishment of a sanitary sas involving strict border control. On 04 March 2022, an active COVID-19 case was confirmed at Vila Central Hospital who had no travel history, indicating transmission at community level. Overall, a total of 8487 confirmed cases have been reported since the beginning of 2022.

Local vaccination campaign was initiated in July 2021. A seroprevalence study documenting population immunity to COVID-19 will inform of the breadth of COVID-19 epidemic in Vanuatu, contributing to the evaluation of undetected infections rate. This identification of vulnerable populations will inform local public Health strategies, including targeted vaccination campaigns.