Soroprevalência Serial de IgG Anti-SARS-CoV-2 em Doadores de Sangue como Parâmetro de Avaliação Epidemiológica da COVID-19 em Fortaleza

Abstract

The investigation of specifics Anti-SARS-CoV-2 antibodies is paramount, not just as a complementary tool to RT-qPCR tests, but also for assessing the level of exposure and attack rate of COVID-19 in a given population. Besides, the identification of possible cases of asymptomatic exposure to the disease and the respective immune response generated is another point evaluated in this Research Project. The study was carried out with 9,902 donors during the period from March to December 2020. This is a retro-prospective, cross-sectional, analytical and epidemiological study, involving blood donors for seroprevalence study to SARS-CoV-2 during the first epidemic wave. All the 9,902 samples from donors were processed and divided into 11 subdistricts in Fortaleza. The results were articulated into 4 categories, comprising the negative (Index (S/C) > 0 e < 0,5); the possibly positive (Index(S/C) ≥ 0,5 e < 1,4); the low positive (Index (S/C) ≥ 1,4 e < 5,79) and the high positive (Index (S/C) ≥ 5,79). The latter two were considered certainly positive, as guaranteed by the manufacturer. Most of the participants presented as general characteristics the age between 16 and 29.9 years (46.37%) (16-69 years), male predominance (62.30%), being brown (73.19%) and holding higher education (50.97%). The majority still had blood type O+ (44.79%), with greater origin among the subdistricts, that one of the Parangaba (13.41%). IgG Anti-SARS-CoV-2 serology was known to be reactive for 1,673 donors (15.90%). Within the four categories of results, it was observed that the higher seroprevalence rate among donors with IgG Anti-SARS-CoV-2 antibody indexes above 1.4 Index (S/C) (certainly positive) were men (P < 0,0001), predominantly aged between 40 and 49.9 years (P < 0,0001), considered brown (P < 0,0001), with only completed elementary school (P < 0,0001), with blood type A+ (P = 0,0029) and from the subdistrict Barra do Ceará (P < 0,0001). When the medians are analysed longitudinally, a peak in the chemiluminescence indexes of IgG Anti-SARS-CoV-2 was observed between May and July, which coincide with the general dates on the increase in the number of cases available in public databases (IntegraSUS/e-SUS) for the period, corroborating this found. Due to the introduction of COVID-19 in Fortaleza, seroprevalence rates showed a continuous and significant increase in the first months, but also a rapid decline, which may be indicating that the humoral response is not lasting. More follow-up populations studies, compared with vaccine monitoring studies, will be essential in order to better understand the dynamics of transmission and ecological adaptation of SARS-CoV-2.