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. 2023 Jan 10;15(1):201.
doi: 10.3390/v15010201.

Seroprevalence of Natural and Acquired Immunity against the SARS-CoV-2 Virus in a Population Cohort from Two Chilean Cities, 2020-2022

Loreto Núñez-Franz  1 , Muriel Ramírez-Santana  2 , Paola Rubilar  3 , Cecilia Vial  4 , Mauricio Apablaza  5 , Claudia González  3 , Macarena Said  1 , Kathya Olivares  2 , Lina Jimena Cortés  4 , Juan Hormazábal  4 , Luis Canales  6 , Pablo Vial  4 , Gloria Icaza  6 , Rubén Quezada-Gaete  2 , Ximena Aguilera  3
Affiliations

Seroprevalence of Natural and Acquired Immunity against the SARS-CoV-2 Virus in a Population Cohort from Two Chilean Cities, 2020-2022

Loreto Núñez-Franz et al. Viruses. .

Abstract

Background: Chile has achieved the highest coverage for vaccines against the SARS-CoV-2 virus worldwide.

Objective: To assess the progression of immunity (natural and acquired by vaccine) in a cohort from two Chilean cities.

Methods: Individuals (n = 386) who participated in three phases of population-based serial prevalence studies were included (2020-2021 and 2022). Presence of SARS-CoV-2 antibodies was measured in serum. Data including time of vaccination and type of vaccine received were analysed with descriptive statistics.

Results: Seroprevalence was 3.6% in the first round and increased to 96.9% in the second and 98.7% in the third. In the third round, 75% of individuals who had received the basal full scheme were seropositive at 180 days or more since their last dose; 98% of individuals who received one booster dose were seropositive at 180 days or more, and 100% participants who received two boosters were seropositive, regardless of time since their last dose. Participants receiving mRNA vaccines had higher seroprevalence rates over time.

Conclusions: The high vaccination coverage in Chile enabled the population to maintain high levels of antibodies. Vaccination boosters are essential to maintain immunity over time, which also depends on the type of vaccine administered.

Keywords: COVID-19; Chile; antibodies; immunity; seroepidemiology; seroprevalence; vaccines.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Scheme of the incorporation, loss and follow-up of the participants in the three rounds of the 2020–2022 seroprevalence study.
Figure 2
Figure 2
Kaplan–Meyer analysis shows probability of antibody loss over time, measured in days, depending on the dose of vaccine received.
Figure 3
Figure 3
Seroprevalence rates in participants who did not receive another vaccine during the period and participants who received one (or two) additional doses during the period between rounds 2 and 3, respectively, according to second-round vaccination status and mean number of days since the last dose.
See this image and copyright information in PMC

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