The COVID-19 pandemic caused by SARS-CoV-2 since December 2019 has caused more than 210 million cases worldwide as of September 1, 2021. New Caledonia (NC) is an ultramarine French territory in the South Pacific so far relatively spared by this pandemic thanks to the establishment of a health lock. The vaccination campaign started locally on 20/01/2021 with the exclusive use of Pfizer's COMIRNATY mRNA vaccine. Vaccination is now offered to anyone over the age of 12. Vaccination against COVID-19 will be mandatory in New Caledonia as of October 31, 2021 for certain exposed populations and for the entire adult population as of December 31, 2021.

Clinical trials of COVID-19 vaccines, including those of mRNA vaccines, have taken care to maintain ethnic diversity within their samples. Efficacy studies have not shown a significant difference in the efficacy of Pfizer COMIRNATY vaccine in white, black American, or Hispanic populations. The response of non-European non-Asian Oceanian populations to Pfizer COMIRNATY vaccination has not been specifically studied at this time. According to the 2019 census in New Caledonia, 41.2% of the population identified themselves as Kanak (Melanesian), 24% as European, 8.3% as Wallisian-Futunian (Polynesian), 11% as mestizo, and 8% as belonging to other communities including Tahitian (Polynesian), Indonesian, Ni-Vanuatu (Melanesian), and Vietnamese communities (8). Some recent data are in favor of a significant variability of susceptibility to pathogens in Oceanian populations, stemming from a genetic inheritance from Neanderthal man and his cousin Denisova man. In a context of vaccine hesitancy, it is therefore important to ensure that the immune response of the New Caledonian population (Melanesian, Polynesian, European or other communities) to vaccination against COVID-19 is similar to that of populations studied in large clinical trials.

Observational equivalence study with prospective data collection. Vaccinated subjects to be included will be identified in the vaccination centers in the Southern Province during the injection of the second dose.

Information and consent collection. Completion of a questionnaire and collection of 4 mL of blood on a dry tube at M1 and M6 months.

Testing for the presence of anti-SARS-CoV-2 antibodies by ELISA (anti-Spike and anti-Nucleoprotein).

Return of the results of the serological analyses to the participants.

Inclusion Criteria:

• Adults from Melanesian, Polynesian, European or other community origin
• Adults vaccinated with 2 doses of Pfizer COMIRNATY vaccine, administered between 3 and 12 weeks apart
• Adults planning to be present in the territory and to be available on both sampling dates (1 and 6 months)

Exclusion Criteria:

• Persons who received the second dose of vaccine more than 12 weeks after the first dose
• Persons vaccinated against COVID-19 with a vaccine other than Pfizer COMIRNATY
• Women who report being pregnant or breastfeeding (where the immune response may be altered)
• Immunocompromised persons (immunosuppressive treatment, immunomodulator, HIV positive, splenectomy, long term corticosteroid therapy, autoimmune diseases such as rheumatoid arthritis, lupus, spondyloarthritis, etc.)
• People who are not intellectually capable of answering the questionnaire
• Persons under guardianship, curatorship or any other legal incapacity
• Persons with documented Covid-19 infection (known positive SARS-CoV-2 serology prior to inclusion, positive PCR or antigen test)