ABSTRACT

Objective

to analyze the vaccine effectiveness in preventing deaths attributed to severe acute respiratory syndrome due to COVID-19 (SARS/COVID-19) in adults and the elderly, in Blumenau, state of Santa Catarina, Brazil, 2021.

this was a population-based study conducted among individuals aged 20 years and older hospitalized with SARS/COVID-19; each death due to SARS/COVID-19 was considered a “case”, and every survivor was considered a “control”; the association between vaccination status and the outcome of “death” was estimated using logistic regression, and vaccine effectiveness was estimated as (1-OR)*100.

The study included 1,756 cases of SARS/COVID-19 (59.2% male, mean age of 56 years, 50.4% with elementary education, 68.4% with comorbidities and 39.1% in intensive care), of whom 398 died (cases) and 1,358 survived (controls); vaccine effectiveness was 74% and 85% (20-59 years old) and 72% and 75% (≥ 60 years old), respectively, for those who were partially vaccinated and fully vaccinated.

Conclusion

vaccines proved to be effective in reducing case fatality ratio due to SARS/COVID-19 in individuals ≥ 20 years old.

Palabras clave
Vacunas contra la Covid-19; Evaluación de Eficacia-Efectividad de Intervenciones; Síndrome Respiratorio Agudo Grave; Covid-19

RESUMEN

Objetivo

analizar la efectividad de la vacuna para prevención de muertes por SRAG-COVID en adultos y ancianos de Blumenau, Santa Catarina, Brasil, 2021.

Método

estudio de base poblacional con personas hospitalizadas por SRAG-COVID mayores de 20 años; las muertes por SRAG-COVID se consideraron casos y todos los supervivientes, controles; la asociación entre el estado de vacunación y la muerte se estimó mediante regresión logística; la efectividad de la vacuna se estimó por (1-OR)*100.

Resultados

participaram do estudo 1.756 casos de SRAG-COVID (59,2% del sexo masculino, edad media de 56 años, 50,4% con estudios primarios, 68,4% con comorbilidades y 39,1% en cuidados intensivos), dos quais 398 foram a óbito (casos) e 1.358 sobreviveram (controles); la efectividad de la vacuna fue del 74% y el 85% (20 a 59 años) y del 72% y el 75% (60 y más años), entre los que tenían vacunación parcial y completa, respectivamente.

Conclusión

las vacunas fueran efectivas para reducir la letalidad del SRAG-covid.

Palabras clave
Vacunas contra la Covid-19; Evaluación de Eficacia-Efectividad de Intervenciones; Síndrome Respiratorio Agudo Grave; Covid-19

INTRODUCTION

Severe acute respiratory syndrome (SARS) is a diffuse and inflammatory form of lung injury, characterized by poor oxygenation, pulmonary infiltrates, and acute onset. Due to its characteristics and the life-threatening risk this disorder poses, much has been discussed about the occurrence of SARS attributed to the novel circulating virus, SARS-CoV^-2.¹1 McIntosh K, Hirsch MS, Bloom A. Severe Acute Respiratory Syndrome (SARS). Uptodate [Internet]. 2023 Jun [cited 2023 July 15]. Available from: https://www.uptodate.com/contents/severe-acute-respiratory-syndrome-sars?topicRef=128323&source=see_link#H26.
https://www.uptodate.com/contents/severe... Cases of SARS-related hospitalization due to COVID-19 (SARS/COVID-19) reported in the Influenza Epidemiological Surveillance Information System (Sistema de Vigilância Epidemiológica da Gripe - SIVEP-Gripe) in Brazil in 2020 were 623,310, representing approximately 61.6% of all cases of SARS. In the following year, these cases increased by 16.7%; and 73.6% of SARS hospitalizations were due to COVID-¹9.²2 Ministério da Saúde (BR). Open Data SUS [Internet]. Brasília: Ministério da Saúde; 2021 [citado 2022 Jun 15]. Disponível em: https://opendatasus.saude.gov.br/dataset?tags=SRAG.
https://opendatasus.saude.gov.br/dataset...

Globally, the number of deaths from the disease was estimated at 6.32 million as of June 20²2.³3 World Health Organization. Coronavirus (COVID-19) Dashboard [Internet]. Geneva: World Health Organization; 2022 [cited 2022 June 22]. Available from: http://covid19.who.int.
http://covid19.who.int.... During the same period, Brazil recorded a total of 669,390 confirmed deaths due to COVID-19. In the Southern macro-region of the country, there were 105,346 deaths, and in the Southern state of Santa Catarina, specifically, 21,940 deaths were report^ed.⁴4 Ministério da Saúde (BR). Secretaria de Vigilância em Saúde. Painel Coronavírus [Internet]. Brasília: Ministério da Saúde; 2022 [citado 2022 Jun 21]. Disponível em: http://covid.saude.gov.br.
http://covid.saude.gov.br.... The five national macro-regions presented different case fatality rat^es,¹1 McIntosh K, Hirsch MS, Bloom A. Severe Acute Respiratory Syndrome (SARS). Uptodate [Internet]. 2023 Jun [cited 2023 July 15]. Available from: https://www.uptodate.com/contents/severe-acute-respiratory-syndrome-sars?topicRef=128323&source=see_link#H26.
https://www.uptodate.com/contents/severe... a factor likely supported by the diversity in the socioeconomic, cultural, and health characteristics of their populatioⁿs.⁵5 Jesus MAS, Hojo-Souza NS, Moraes TR, Guidoni DL, Souza FSH. Profile of Brazilian inpatients with COVID-19 vaccine breakthrough infection and risk factors for unfavorable outcome. Rev Panam Salud Publica. 2022;46:e106. doi: 10.26633/RPSP.2022.106.
https://doi.org/.26633/RPSP.2022.106....

In early 2021, a significant portion of the world began mass vaccination campaigns using newly approved vaccines against COVID-¹9.⁶6 Dagan N, Barda N, Kepten E, Miron O, Perchik S, Katz MA, et al. BNT162b2 mRNA Covid-19 Vaccine in a Nationwide Mass Vaccination Setting. N Engl J Med. 2021;384(15):1412-23. doi: 10.1056/NEJMoa2101765.
https://doi.org/.1056/NEJMoa2101765.... .⁷7 Villela DAM, Noronha TG, Bastos LS, Pacheco AG, Cruz OG, Carvalho LM, et al. Effectiveness of mass vaccination in Brazil against severe COVID-19 cases. MedRxiv [Preprint]. 2021. doi: 10.1101/2021.09.10.21263084. Vaccination commenced in Brazil in January 2021, with the administration of the AstraZeneca/Fiocruz and Sinovac/Butantan vaccines; the Pfizer/Wyeth vaccine was included in May of the same year, and the Janssen vaccine in June, totaling four available vaccine products against the disease in the count^ry.⁴4 Ministério da Saúde (BR). Secretaria de Vigilância em Saúde. Painel Coronavírus [Internet]. Brasília: Ministério da Saúde; 2022 [citado 2022 Jun 21]. Disponível em: http://covid.saude.gov.br.
http://covid.saude.gov.br.... Evaluations of vaccine effectiveness are crucial not only to understand its effect on reducing infection and disease, but also to guide relevant public polici^es.⁸8 Patel MK, Bergeri I, Bresee JS, Cowling BJ, Crowcroft NS, Fahmy K, et al. Evaluation of post-introduction COVID-19 vaccine effectiveness: summary of interim guidance of the World Health Organization. Vaccine. 2021;39(30):4013-24. doi: 10.1016/j.vaccine.2021.05.099.
https://doi.org/.1016/j.vaccine.2021.05.... Norway achieved a vaccine effectiveness in preventing deaths estimated at 46.9% after the first dose and 93.4% after the second do^se.⁹9 Starrfelt J, Danielsen AS, Buanes EA, Juvet LK, Lyngstad TM, Rø GØI, et al. Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, July–November 2021. BMC Medicine. 2022;20(1):278. doi: 10.1186/s12916-022-02480-4.
https://doi.org/10.1186/s12916-022-02480... An analysis of clinical trials for vaccines, using the World Health Organization (WHO) Emergency Use Listing, estimated variable vaccine effectiveness, ranging from 90% to 99% after two doses, against the “death” outcome. These values were lower after a single dose: 70% to 90% against the same outco^me.¹⁰10 Higdon MM, Wahl B, Jones CB, Rosen JG, Truelove SA, Baidya A, et al. A systematic review of coronavirus disease 2019 vaccine efficacy and effectiveness against severe acute respiratory syndrome coronavirus 2 infection and disease. Open Forum Infect Dis. 2022;9(6):ofac138. doi: 10.1093/ofid/ofac138.
https://doi.org/.1093/ofid/ofac138.... A meta-analysis of records from 51 studies estimated vaccine effectiveness in preventing deaths from COVID-19 at 58.4% for the partial vaccination status and 98.1% for the full vaccination stat^us.¹¹11 Zheng C, Shao W, Chen X, Zhang B, Wang G, Zhang W. Real-world effectiveness of COVID-19 vaccines: a literature review and meta-analysis. Int J Infect Dis. 2022;114:252-60. doi: 10.1016/j.ijid.2021.11.009.
https://doi.org/.1016/j.ijid.2021.11.009... In Brazil, the vaccination effectiveness for the outcome of “death” ranged from 35.3% for individuals aged 80 years and older, with a partial vaccination schedule, to 84.5% in the age group of 40 to 59 years with a full vaccination schedu^le.⁷7 Villela DAM, Noronha TG, Bastos LS, Pacheco AG, Cruz OG, Carvalho LM, et al. Effectiveness of mass vaccination in Brazil against severe COVID-19 cases. MedRxiv [Preprint]. 2021. doi: 10.1101/2021.09.10.21263084. According to another Brazilian study, conducted with national hospitalization and vaccination data, vaccine effectiveness against death from COVID-19 with full vaccination schedule ranged from 57.7% to 89.9%, while with a single-dose schedule, effectiveness ranged from 35.3% to 61.^8%.¹²12 Cerqueira-Silva T, Andrews JR, Boaventura VS, Ranzani OT, Oliveira VA, Paixão ES, et al. Effectiveness of CoronaVac, ChAdOx1 nCoV-19, BNT162b2, and Ad26.COV2 among individuals with previous SARS-CoV-2 infection in Brazil: a test-negative, case-control study. Lancet Infect Dis. 2022;22(6):791-801. doi: 10.1016/S1473-3099(22)00140-2.
https://doi.org/.1016/S1473-3099(22)0014...

Data on vaccine effectiveness against COVID-19 in reducing the risk of death in people with specific health conditions are scarce, such as in the case of people hospitalized with SARS/COVID-19 in Southern Brazil.

The objective of this study was to estimate vaccine effectiveness in reducing the risk of death in adults and older adults with SARS/COVID-19 living in the municipality of Blumenau, state of Santa Catarina, Brazil, in 2021.

METHODS

This was a population-based case-control study on SARS/COVID-19 cases with onset of symptoms occurring between January 1 and December 31, 2021, in residents of Blumenau, state of Santa Catarina.

The municipality of Blumenau, state of Santa Catarina, founded by German immigrants in the Médio Vale do Itajaí (26° 55’ 08” South Latitude and 49° 03’ 57” West Longitude), had an estimated population of 366,418 inhabitants and a gross domestic product (GDP) per capita of BRL 48,416.09 in 2021. Blumenau is an important industrial, technological and university hub in the sta^te.¹³13 Instituto Brasileiro de Geografia e Estatística. Cidades e Estados: Blumenau [Internet]. Rio de Janeiro: Instituto Brasileiro de Geografia e Estatística; 2022 [citado 2022 Jun 15]. Disponível em: https://cidades.ibge.gov.br/brasil/sc/blumenau/panorama.
https://cidades.ibge.gov.br/brasil/sc/bl...

Participants and Data Sources

All people with SARS/COVID-19 and a clinical picture of influenza-like illness who presented with dyspnea/respiratory distress or persistent chest pressure or oxygen saturation level below 95% on room air or blue discoloration of the lips or face, confirmed by RT-PCR te^st,¹⁴14 Ministério da Saúde (BR). Guia de Vigilância Epidemiológica: emergência de saúde pública de importância nacional pela doença pelo coronavírus 2019 [Internet]. Brasília: Ministério da Saúde; 2020 [citado 2023 Jul 4]. Disponível em: https://www.saude.sc.gov.br/coronavirus/arquivos/af_gvs_coronavirus_6ago20_ajustes-finais-2.pdfc.
https://www.saude.sc.gov.br/coronavirus/... aged 20 years or older, living in Blumenau, with completed investigation and available in the SIVEP-Gripe database, were considered eligible for the study. The anonymized SIVEP-Gripe database was made available to researchers in April 2022.

“Cases” of SARS/COVID-19 resulting in death during the period established for the study were considered: n = 398. Based on the definition of death due to SARS/COVID-19 described here, additional information related to deaths in the System’s database was investigated by the Death Investigation Service of the Epidemiological Surveillance, in Blumenau, which checks the quality of the information recorded in Death Certificates (DCs) by reviewing outpatient and/or hospital medical records. All cases of SARS/COVID-19 that survived during the same study period were defined as “controls”: n = 1,360. Taking into consideration a first-dose vaccine coverage of 30% for 398 cases, and 40% for 1,358 controls, a study power of 97% was estimated for an odds ratio (OR) of 0.63 and a 95% confidence interval (95%CI). Furthermore, considering vaccine coverage with two doses or a single dose of 20% for 398 cases, and 30% for 1,358 controls, a study power of 98% was estimated for an OR = 0.58 and 95%CI (Figure 1).

Information on vaccination status (exposure variable) was reviewed at the Immunization Coordination of the Municipal Health Department of Blumenau.

Exposure Variable

Regarding vaccination status, participants were classified as “unvaccinated”, “partially vaccinated” (received 1 dose) or “fully vaccinated” (received one dose of the single-shot Janssen vaccine, or received two doses of the others), regardless of vaccine type, brand or batch. In Blumenau, the first doses of vaccine were administered on January 20, 2021. Booster doses were not taken into account, as they only began from epidemiological week 37 of 2021, in the municipality.

Confounding variables

The following adjustment variables, available in the database, were selected:

• sex (male; female);

• age group (in full years: 20 to 59; 60 to 79; 80 and older);

• self-reported race/skin color (White; non-White);

• schooling (illiterat^e; 1st ^to 5th grade of elementary schoo^l; 6th ^to 9th grade of elementary school; high school; higher education);

• place of residence (grouped neighborhoods);

• presence and number of comorbidities;

• type of comorbidity/risk factor (Down syndrome; diabetes mellitus; immunodeficiency; cardiovascular disease; chronic liver disease; chronic neurological disorders; chronic kidney disease; chronic hematologic disorders; asthma; other chronic lung diseases; obesity; and being a puerperal woman);

• influenza vaccination in the previous year (yes; no); and

• admission to the Intensive Care Unit (ICU) (yes; no).

The place of residence took into account the declared neighborhood, grouped by degree of urbanization according to the number of plots registered for agricultural use: (i) without any plots – Boa Vista, Bom Retiro, Centro, Itoupava Norte, Itoupava Seca, Jardim Blumenau, Ponta Aguda, Ribeirão Fresco, Victor Konder, Vila Formosa, Vila Nova and Vorstadt –; (ii) with up to 10 plots – Água Verde, Badenfurt, Da Glória, Do Salto, Escola Agrícola, Fortaleza, Garcia, Nova Esperança, Salto do Norte, Salto Weissbach, Tribess, Valparaíso, Velha, Velha Central and Velha Grande –; and (iii) with 10 to 20 plots – Progresso, Fidélis, Fortaleza Alta, Itoupava Central, Itoupavazinha, Passo Manso, Testo Salto and Vila Itoupa^va.¹⁵15 Prefeitura de Blumenau (SC). Pensar Blumenau: Plano Diretor 2015-2016 - Proposta da lei de revisão do plano diretor de Blumenau [Internet]. Blumenau: Secretaria de Planejamento Urbano; 2015 [citado 2022 Jun 15]. 61 p. Disponível em: https://www.blumenau.sc.gov.br/blumenau/audiencias-publicas&download=adc60461c8f7c9404dff7642cb2d2e1e.
https://www.blumenau.sc.gov.br/blumenau/...

Statistical methods

The variables were examined according to the type of distribution: continuous variables were presented by measures of central tendency and dispersion; and categorical variables, by absolute and relative frequencies. As these are secondary data, the presence of incompleteness was checked, and variables with more than 10% incompleteness were excluded.

The comparison of means was performed using Student’s t-test, and the comparison of proportions, using Pearson’s chi-square test. The association between vaccination status (partial; complete) and the occurrence of death, both overall and by age group, was estimated by means of odds ratio (OR) and 95%CI obtained using unconditional logistic regression, crude and adjusted for sex, age, schooling, place of residence, number of comorbidities, and previous influenza vaccination. All study variables with a p-value < 0.20 in the univariate analysis were included in the adjusted models.

Vaccine effectiveness was estimated using the following formula: 1 - OR of vaccination between cases and controls *1⁰⁰.¹⁶16 Sullivan SG, Tchetgen Tchetgen EJ, Cowling BJ. Theoretical basis of the test-negative study design for assessment of influenza vaccine effectiveness. Am J Epidemiol. 2016;184(5):345-53. doi 10.1093/aje/kww064. Model adjustment was estimated using the Hosmer-Lemeshow test. Statistical analyses were performed using the Stata 11.2. A p-value < 0.05 was considered statistically significant.

Ethical aspects

This study is part of the research project entitled “COVID-19 vaccine effectiveness in Blumenau, state of Santa Catarina: a case-control study”, approved by the Human Research Ethics Committee (HREC), of the Fundação Universidade Regional de Blumenau (FURB), on August 7, 2021: Certificate of Submission for Ethical Appraisal (CAAE) No. 46513121.5.0000.5370; Opinion No. 4,891,763. Due to the use of secondary data, the project was exempt from requiring the participants to sign the Free and Informed Consent Form (FICF).

RESULTS

There were 2,570 cases of SARS in residents of the municipality of Blumenau in 2021, and among them, 1,829 were confirmed as COVID-19 through RT-PCR test or antigen test. Of these, 1,756 people aged 20 years or older took part in the study, of whom 398 died from SARS/COVID-19 (cases) and 1,358 survived (controls). Figure 1 shows the participant selection flowchart.

Regarding data completeness for study variables, sex, age group, comorbidities, and COVID-19 vaccination status had 100% completeness. The percentage of incompleteness for the other variables was 5.2% for schooling, 4.2% for previous influenza vaccination, 2.5% for number of comorbidities, 2% for race/skin color, 1.5% for ICU admission, 0.5% for place of residence, and 0.2% for deaths.

Table 1 shows some of the clinical and epidemiological characteristics of the cases and controls. There was no statistically significant difference in sex and race/skin color between cases and controls. The mean age was higher among cases (66.3 versus 53.1 years; p-value < 0.001). In addition, a higher proportion of people with lower level of education, three or more comorbidities, without previous influenza vaccination and those who required ICU admission were observed among cases. As for associated comorbidities/risk factors, chronic cardiovascular disease (47.7%), obesity (35.6%), diabetes mellitus (31.9%), other chronic lung diseases, chronic kidney disease (4,2%), asthma (4,2%), chronic neurological disorders (3.6%), immunodeficiency (3.0%), chronic liver disease (0.8%), chronic hematological disorders (0.5%), being a puerperal woman (0.3%) and Down syndrome (0.1%) (data not shown in the table). Vaccination coverage, both for the first dose and for the second dose or single dose, was higher in the control group.

Table 2 shows the results of the crude and adjusted analyses of the association between vaccination status and death, by dose and age group, in people with SARS. A higher chance of protection against death was found among vaccinated people, both among those who received one dose and those who received two doses.

Figure 2 presents the vaccine effectiveness in reducing deaths among people with SARS/COVID-19.

DISCUSSION

Vaccination, adjusted for confounding variables, proved to be effective in reducing deaths from SARS/COVID-19. Even in populations aged 60 years or older and with incomplete vaccination status, vaccine effectiveness was above 70%.

When characterizing the study population in the clinical and epidemiological terms, it could be seen that the majority of people with SARS/COVID-19 were male, a finding similar to that of other national¹⁷17 Faria MR, Prates BCR, Morais TSL, Correa T, Almeida MC, Vicente TMB. Coleta e análise de dados acerca da síndrome respiratória aguda grave e do novo coronavírus: epidemiologia no Brasil e no estado de Santa Catarina – 2020/2021. Rev Nucleo Estudos Economia Catarinense [Internet]. 2021[citado 2022 Jun 15];10(19):90–111. Disponível em: https://revistanecat.ufsc.br/index.php/revistanecat/article/view/4851.-¹⁹19 Mascarello KC, Vieira ACBC, Souza ASS, Marcarini WD, Barauna VG, Maciel ELN. Hospitalização e morte por COVID-19 e sua relação com determinantes sociais da saúde e morbidades no Espírito Santo: um estudo transversal. Epidemiol Serv Saude. 2021;30(3):e2020919. doi: 10.1590/S1679-49742021000300004.
https://doi.org/.1590/S1679-497420210003... and international studi^es.²⁰20 Fang X, Li S, Yu H, Wang P, Zhang Y, Chen Z, et al. Epidemiological, comorbidity factors with severity and prognosis of COVID-19: a systematic review and meta-analysis. Aging (Albany NY). 2020;12(13):12493–503. doi: 10.18632/aging.103579.
https://doi.org/.18632/aging.103579.... The age group of 20 to 59 years was the most affected by SARS/COVID-19, consistent with findings from a national stu^dy.²¹21 Niquini RP, Lana RM, Pacheco AG, Cruz OG, Coelho FC, Carvalho LM, et al. SRAG por COVID-19 no Brasil: descrição e comparação de características demográficas e comorbidades com SRAG por influenza e com a população geral. Cad Saude Publica. 2020;36(7). doi: 10.1590/0102-311x00149420.
https://doi.org/10.1590/0102-311x0014942... However, SARS/COVID-19 hospitalizations were related to the oldest age groups, especially those aged 60 years and older.¹⁸18 Sousa EL, Gaído SB, Sousa RA, Cardoso OO, Matos Neto EM, Menezes Júnior JMP, et al. Profile of hospital admissions and deaths due to severe acute respiratory syndrome caused by COVID-19 in Piauí, Brazil: a descriptive study, 2020-2021. Epidemiol Serv Saude. 2022;31(1):e2021836. doi: 10.1590/S1679-49742022000100009.
https://doi.org/10.1590/S1679-4974202200... ,¹⁹19 Mascarello KC, Vieira ACBC, Souza ASS, Marcarini WD, Barauna VG, Maciel ELN. Hospitalização e morte por COVID-19 e sua relação com determinantes sociais da saúde e morbidades no Espírito Santo: um estudo transversal. Epidemiol Serv Saude. 2021;30(3):e2020919. doi: 10.1590/S1679-49742021000300004.
https://doi.org/.1590/S1679-497420210003...

In this sample from Blumenau, SARS/COVID-19 cases had a higher frequency of comorbidities when compared to controls. This finding is consistent with those of other studies.²¹21 Niquini RP, Lana RM, Pacheco AG, Cruz OG, Coelho FC, Carvalho LM, et al. SRAG por COVID-19 no Brasil: descrição e comparação de características demográficas e comorbidades com SRAG por influenza e com a população geral. Cad Saude Publica. 2020;36(7). doi: 10.1590/0102-311x00149420.
https://doi.org/10.1590/0102-311x0014942... -²³23 Peres IT, Bastos LSL, Gelli JGM, Marchesi JF, Dantas LF, Antunes BBP, et al. Sociodemographic factors associated with COVID-19 in-hospital mortality in Brazil. Public Health. 2021;192:15-20. doi: 10.1016/j.puhe.2021.01.005.
https://doi.org/.1016/j.puhe.2021.01.005... The most prevalent comorbidities were cardiovascular disease, obesity, diabetes mellitus, and other chronic lung diseases unrelated to the current COVID-19 disease. The frequency of these comorbidities in cases of SARS-COVID-19 decreased significantly when compared to cases with mild COVID-¹⁹.²⁴24 Wu Z, McGoogan JM. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72.314 cases from the Chinese Center for Disease Control and Prevention. JAMA. 2020;323(13):1239-42. doi: 10.1001/jama.2020.2648.
https://doi.org/.1001/jama.2020.2648.... It is also noteworthy that just under half of the individuals hospitalized due to SARS/COVID-19 required ICU admissions, a figure close to the national findin^gs.²³23 Peres IT, Bastos LSL, Gelli JGM, Marchesi JF, Dantas LF, Antunes BBP, et al. Sociodemographic factors associated with COVID-19 in-hospital mortality in Brazil. Public Health. 2021;192:15-20. doi: 10.1016/j.puhe.2021.01.005.
https://doi.org/.1016/j.puhe.2021.01.005...

When examining the profile of cases that progressed to death due to SARS/COVID-19, some peculiarities were observed, including the oldest age group (between 60 and 79 years), lower level of schooling (illiterate or with an education level up to elementary school) and the presence of comorbidities. The association between the risk of negative outcomes of COVID-19 and increasing age was identified at the beginning of the pandemic,²⁴24 Wu Z, McGoogan JM. Characteristics of and important lessons from the coronavirus disease 2019 (COVID-19) outbreak in China: summary of a report of 72.314 cases from the Chinese Center for Disease Control and Prevention. JAMA. 2020;323(13):1239-42. doi: 10.1001/jama.2020.2648.
https://doi.org/.1001/jama.2020.2648.... ,²⁵25 Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study. Lancet. 2020;395(10229):1054–62. doi: 10.1016/S0140-6736(20)30566-3.
https://doi.org/.1016/S0140-6736(20)3056... although it has not been extensively explored in the context of SARS/COVID-19. Lower levels of schooling were associated with deaths, both in Santa Catari^na,¹⁷17 Faria MR, Prates BCR, Morais TSL, Correa T, Almeida MC, Vicente TMB. Coleta e análise de dados acerca da síndrome respiratória aguda grave e do novo coronavírus: epidemiologia no Brasil e no estado de Santa Catarina – 2020/2021. Rev Nucleo Estudos Economia Catarinense [Internet]. 2021[citado 2022 Jun 15];10(19):90–111. Disponível em: https://revistanecat.ufsc.br/index.php/revistanecat/article/view/4851. and in Brazil as a whole.¹⁸18 Sousa EL, Gaído SB, Sousa RA, Cardoso OO, Matos Neto EM, Menezes Júnior JMP, et al. Profile of hospital admissions and deaths due to severe acute respiratory syndrome caused by COVID-19 in Piauí, Brazil: a descriptive study, 2020-2021. Epidemiol Serv Saude. 2022;31(1):e2021836. doi: 10.1590/S1679-49742022000100009.
https://doi.org/10.1590/S1679-4974202200... -²³23 Peres IT, Bastos LSL, Gelli JGM, Marchesi JF, Dantas LF, Antunes BBP, et al. Sociodemographic factors associated with COVID-19 in-hospital mortality in Brazil. Public Health. 2021;192:15-20. doi: 10.1016/j.puhe.2021.01.005.
https://doi.org/.1016/j.puhe.2021.01.005... This can be explained, at least in part, by expressing educational and cultural characteristics associated with knowledge about the disease and its complications, as well as by representing an approximation of worse economic conditions.

In this study, vaccine effectiveness against SARS/COVID-19 showed a greater protective effect in the youngest age group of the sample, from 20 to 59 years old, and among those with the complete vaccination schedule, i.e., two doses or a single dose. In the state of Rio Grande do Sul, the State Center for Health Surveillance found 58% effectiveness of partial COVID-19 vaccination in the occurrence of SARS/COVID-19 among the elderly; and over 90% in the population with a complete vaccination schedule, among those aged 20 to 59 yea^rs.²⁶26 Secretaria de Saúde (RS). Centro Estadual de Vigilância em Saúde do Rio Grande do Sul. Avaliação da efetividade da vacinação contra a covid-19 no Rio Grande do Sul [Internet]. Porto Alegre: Secretaria de Saúde; 2021 [citado 2022 Jun 18]. Disponível em: https://saude.rs.gov.br.
https://saude.rs.gov.br.... Consistent with the findings of this study, it could be seen that the estimates of vaccine effectiveness in preventing deaths are higher in the younger age gro^up.⁷7 Villela DAM, Noronha TG, Bastos LS, Pacheco AG, Cruz OG, Carvalho LM, et al. Effectiveness of mass vaccination in Brazil against severe COVID-19 cases. MedRxiv [Preprint]. 2021. doi: 10.1101/2021.09.10.21263084. Such differences in vaccine effectiveness are likely attributed to the different vaccination schedules (the complete vaccination schedule provides greater stimulus to the immune response) and the different age groups [in older adults, the immunosenescence process (changes in the immune system caused by aging), combined with the presence of comorbidities, hinders the immune response].⁹9 Starrfelt J, Danielsen AS, Buanes EA, Juvet LK, Lyngstad TM, Rø GØI, et al. Age and product dependent vaccine effectiveness against SARS-CoV-2 infection and hospitalisation among adults in Norway: a national cohort study, July–November 2021. BMC Medicine. 2022;20(1):278. doi: 10.1186/s12916-022-02480-4.
https://doi.org/10.1186/s12916-022-02480... ,²⁷27 Orellana JDY, Cunha GM, Marrero L, Leite IC, Domingues CMAS, Horta BL. Changes in the pattern of COVID-19 hospitalizations and deaths after substantial vaccination of the elderly in Manaus, Amazonas State, Brazil. Cad Saude Publica. 2022;38(5):PT192321. doi: 10.1590/0102-311XPT192321.
https://doi.org/.1590/0102-311XPT192321....

As the study used secondary data, it was subject to information bias, given that the data may contain diagnostic errors, failures, and incompleteness in the records. In addition, the effectiveness by type of vaccine administered was not analyzed, since this information was not available in the database used at the time of the study. Nevertheless, this study depicted real-world vaccine effectiveness and its use conditions.

It can be concluded that vaccination against COVID-19 proved to be effective in reducing the risk of death among people aged 20 years and older with SARS/COVID-19 in Blumenau in 2021. It is recommended to expand vaccine coverage and booster doses as strategies to prevent deaths due to SARS/COVID-19, especially among the population aged 60 years and older, with low level of schooling and the presence of comorbidities.

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