Esporte SARS-CoV-2 antibody prevalence in Brazil: results from two successive nationwide serological household surveys

Esporte SARS-CoV-2 antibody prevalence in Brazil: results from two successive nationwide serological household surveys

Esporte SummaryBackgroundPopulation-based data on COVID-19 are essential for guiding policies. There are few such studies, particularly from low or middle-income countries. Brazil is currently a hotspot for COVID-19 globally. We aimed to investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody prevalence by city and according to sex, age, ethnicity group, and socioeconomic status, and compare seroprevalence estimates with official statistics on deaths and cases.

MethodsIn this repeated cross-sectional study, we did two seroprevalence surveys in 133 sentinel cities in all Brazilian states. We randomly selected households and randomly selected one individual from all household members. We excluded children younger than 1 year. Presence of antibodies against SARS-CoV-2 was assessed using a lateral flow point-of-care test, the WONDFO SARS-CoV-2 Antibody Test (Wondfo Biotech, Guangzhou, China), using two drops of blood from finger prick samples. This lateral-flow assay detects IgG and IgM isotypes that are specific to the SARS-CoV-2 receptor binding domain of the spike protein. Participants also answered short questionnaires on sociodemographic information (sex, age, education, ethnicity, household size, and household assets) and compliance with physical distancing measures.

FindingsWe included 25 025 participants in the first survey (May 14–21) and 31 165 in the second (June 4–7). For the 83 (62%) cities with sample sizes of more than 200 participants in both surveys, the pooled seroprevalence increased from 1·9% (95% CI 1·7–2·1) to 3·1% (2·8–3·4). City-level prevalence ranged from 0% to 25·4% in both surveys. 11 (69%) of 16 cities with prevalence above 2·0% in the first survey were located in a stretch along a 2000 km of the Amazon river in the northern region. In the second survey, we found 34 cities with prevalence above 2·0%, which included the same 11 Amazon cities plus 14 from the northeast region, where prevalence was increasing rapidly. Prevalence levels were lower in the south and centre-west, and intermediate in the southeast, where the highest level was found in Rio de Janeiro (7·5% [4·2–12·2]). In the second survey, prevalence was similar in men and women, but an increased prevalence was observed in participants aged 20–59 years and those living in crowded conditions (4·4% [3·5–5·6] for those living with households with six or more people). Prevalence among Indigenous people was 6·4% (4·1–9·4) compared with 1·4% (1·2–1·7) among White people. Prevalence in the poorest socioeconomic quintile was 3·7% (3·2–4·3) compared with 1·7% (1·4–2·2) in the wealthiest quintile.

InterpretationAntibody prevalence was highly heterogeneous by country region, with rapid initial escalation in Brazil’s north and northeast. Prevalence is strongly associated with Indigenous ancestry and low socioeconomic status. These population subgroups are unlikely to be protected if the policy response to the pandemic by the national government continues to downplay scientific evidence.

FundingBrazilian Ministry of Health, Instituto Serrapilheira, Brazilian Collective Health Association, and the JBS Fazer o Bem Faz Bem.

IntroductionAlthough the need for population-based data on COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is widely recognised,

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few nationwide surveys are available.

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Spain. Estudio ENE-Covid-19: Segunda Ronda. Estudio Nacional de Sero-Epdemiologia de la Infección por SARS-CoV-2 en España. Madrid, España.

The first COVID-19 case in Brazil was reported on Feb 26, 2020, in the city of São Paulo, and as of Sept 4, approximately 125 000 deaths have been reported.

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Three population-based antibody surveys done in the south and southeast regions of Brazil showed prevalence ranging from 0·05% to 2·1%.

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Pellanda LC Wendland EM McBride AJA et al.Sensitivity and specificity of a rapid test for assessment of exposure to SARS-CoV-2 in a community-based setting in Brazil.

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Comitê Técnico do Inquérito Epidemiológico SARS-CoV-2

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The government’s response to the pandemic has been marked by controversy, with the country’s president, Jair Bolsonaro, opposing physical distancing measures and downplaying the importance of COVID-19.

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Testing is limited to patients with severe illnesses and evidence suggests that COVID-19 deaths are undercounted.

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Thus, periodic, population-based data on the pandemic are urgently needed.

Research in context

Evidence before this study

Brazil has become a global hotspot for the COVID-19 pandemic in terms of reported cases and deaths. We searched PubMed, Web of Science and Scielo for papers in any language, published from Jan 1, 2019 onwards. We used the search terms: ((“severe acute respiratory syndrome coronavirus 2”[All Fields] OR “severe acute respiratory syndrome coronavirus 2”[All Fields] OR “ncov”[All Fields] OR “2019-nCoV”[All Fields] OR “COVID-19”[All Fields] OR “SARS-CoV-2”[All Fields] AND (Brasil OR Brazil)). Globally, few nationwide population-based studies on the prevalence of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are available, and none from low-income or middle-income countries. Existing studies in Brazil have focused on the more developed parts of the country, represented by the southern and southeastern regions.

Added value of this study

We did two household surveys in the most populous cities in all 133 mesoregions of Brazil, covering 26 states and the Federal District. We included more than 25 000 participants in the period May 14–21 and over 32 000 in June 4–7. We documented an increase in prevalence during this time interval, with strong concentration in 11 cities along the Amazon River, where prevalence was as high as 25% in both surveys. In the second survey, rapid increases in prevalence were also observed in the northeast. High-prevalence areas are poorer and less well-served by health and other services than areas in the rest of the country are. Prevalence among Indígena (Indigenous) individuals was over four times higher than among Branco (White) people, and prevalence in the poorest socioeconomic quintile was over twice as high as in the richest quintile.

Implications of all the available evidence

The poorest areas of Brazil, particularly the Amazon River basin, were the first to present high prevalence of antibodies against SARS-CoV-2, by contrast with the initially low prevalence observed in the southern and centre-western regions. Our geographical-level and individual-level analyses showed remarkable inequality in the prevalence of infection, with poverty and Indígeno ethnicity driving the progression of the pandemic in the country. The controversial handling of the epidemic by the federal government is likely to have contributed to the rapid spread of COVID-19 in the country’s most susceptible populations.

We aimed to investigate antibody prevalence by city and according to sex, age, ethnicity group, and socioeconomic status, and compare seroprevalence estimates with official statistics on deaths and cases.

Methods Study design and samplingWe did nationwide seroprevalence surveys on May 14–21, and June 4–7, 2020, in 133 sentinel cities from the 26 Brazilian states and the Federal District (figure 1). Brazil’s 27 federation units are divided by the Brazilian Institute of Geography and Statistics into 133 intermediary regions. The most populous city in each region was selected.

We selected 25 urban census tracts with probability proportionate to size in each sentinel city, and ten households at random in each tract, using maps and household listings made available by the Brazilian Institute of Geography and Statistics. One individual was randomly selected from a listing of all household members. Children younger than 1 year were excluded because parents or guardians were not likely to have consented to the collection of blood. If the selected individual did not provide a sample, another household member was randomly selected. If this person also refused, the interviewers moved on to the next household on the right, which was also selected in the case of absent residents.

Interviewers were tested on the day before fieldwork using the antibody test and only participated in the study if the result was negative, and were provided with personal protective equipment (aprons, gloves, surgical face masks, and shoe and hair covers) that were discarded as hospital waste after each interview. Ethics approval was obtained from the Brazilian’s National Ethics Committee (CAAE 30721520.7.1001.5313), with written informed consent from all participants or by parents for minors. Positive cases were reported to the municipal COVID-19 surveillance systems; participants agreed to the disclosure in the consent form.

 ProceduresPrevalence of antibodies was assessed with a rapid point-of-care test, the WONDFO SARS-CoV-2 Antibody Test (Wondfo Biotech, Guangzhou, China), using two drops of blood from finger prick samples. This lateral-flow assay detects IgG and IgM isotypes that are specific to the SARS-CoV-2 receptor binding domain of the spike protein. By pooling the results from four validation studies, weighted by sample sizes, sensitivity was estimated at 84·8% (95% CI 81·4–87·8%) and specificity at 99·0% (97·8–99·7).

10

Pellanda LC Wendland EM McBride AJA et al.Sensitivity and specificity of a rapid test for assessment of exposure to SARS-CoV-2 in a community-based setting in Brazil.

Specificity estimates were obtained with frozen sera and might have been underestimated.

16

Whitman JD Hiatt J Mowery CT et al.Test performance evaluation of SARS-CoV-2 serological assays.

In early April 2020, we did a household probability survey in nine cities in the state of Rio Grande do Sul,

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Silveira MF Barros AJD Horta BL et al.Population-based surveys of antibodies against SARS-CoV-2 in Southern Brazil.

when the pandemic was at an early stage in the state. Of 4188 participants we found only two (
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