RESUMEN
To achieve global herd immunity, widespread vaccination is the most effective strategy. Vaccines stimulate the immune system, generating cytokines and chemokines, isotype antibodies, and neutralizing antibodies; all these molecules collectively provide a more comprehensive characterization of the immune response post-vaccination. We conducted a longitudinal study in northwestern Mexico, involving 120 individuals before vaccination and after the first dose of the SARS-CoV-2 vaccine, and 46 individuals after their second dose. Our findings reveal that antibody levels stabilize over time; cytokine levels generally increase following the first dose but decrease after the second dose and higher than normal levels in IgG1 and IgG3 concentrations are present. Most of the innate cytokines determined in this study were higher after the first dose of the vaccine. Regardless of previous infection history, this finding suggests that the first dose of the vaccine is crucial and may stimulate immunity by enhancing the innate immune response. Conversely, increased levels of IL-4, indicative of a Th2 response, were found in individuals without prior exposure to the virus and in those vaccinated with CoronaVac. These results suggest that the immune response to COVID-19 vaccines is multi-faceted, with preexisting immunity potentiating a more robust innate response. Vaccine type plays a critical role, with genetic vaccines favoring a Th1 response and inactivated vaccines like CoronaVac skewing toward a Th2 profile.
Asunto(s)
Anticuerpos Neutralizantes , Anticuerpos Antivirales , Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , ChAdOx1 nCoV-19 , Citocinas , SARS-CoV-2 , Humanos , COVID-19/inmunología , COVID-19/prevención & control , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/inmunología , Masculino , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/administración & dosificación , Citocinas/inmunología , Femenino , Adulto , Persona de Mediana Edad , Anticuerpos Neutralizantes/sangre , Anticuerpos Neutralizantes/inmunología , Vacuna BNT162/inmunología , Vacuna BNT162/administración & dosificación , México , Estudios Longitudinales , ChAdOx1 nCoV-19/inmunología , ChAdOx1 nCoV-19/administración & dosificación , SARS-CoV-2/inmunología , Células Th2/inmunología , Células TH1/inmunología , Inmunoglobulina G/sangre , Vacunación , Vacunas de Productos Inactivados/inmunología , Vacunas de Productos Inactivados/administración & dosificación , Adulto Joven , AncianoRESUMEN
Global investment in developing COVID-19 vaccines has been substantial, but vaccine hesitancy has emerged due to misinformation. Concerns about adverse events, vaccine shortages, dosing confusion, mixing vaccines, and access issues contribute to hesitancy. Initially, the WHO recommended homologous vaccination (same vaccine for both doses), but evolving factors led to consideration of heterologous vaccination (different vaccines). The study compared reactogenicity and antibody response for both viral protein spike (S) and nucleocapsid (N) in 205 participants who received three vaccination regimens: same vaccine for all doses (Pfizer), two initial doses of the same vaccine (CoronaVac or AstraZeneca), and a Pfizer booster. ChAdOx1 and BNT162b2 vaccines were the most reactogenic vaccines, while CoronaVac vaccine was the least. ChAdOx1 and BNT162b2 achieved 100% of S-IgG seropositivity with one dose, while CoronaVac required two doses, emphasizing the importance of the second dose in achieving complete immunization across the population with different vaccine regimes. Pfizer recipients showed the highest S-IgG antibody titers, followed by AstraZeneca recipients, both after the first and second doses. A third vaccine dose was essential to boost the S-IgG antibodies and equalize the antibody levels among the different vaccine schedules. CoronaVac induced N-IgG antibodies, while in the Pfizer and AstraZeneca groups, they were induced by a natural infection, reinforcing the role of N protein as a biomarker of infection.
Asunto(s)
Anticuerpos Antivirales , Vacunas contra la COVID-19 , COVID-19 , Esquemas de Inmunización , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven , Anticuerpos Antivirales/sangre , Formación de Anticuerpos/inmunología , Vacuna BNT162/administración & dosificación , Vacuna BNT162/inmunología , ChAdOx1 nCoV-19/inmunología , ChAdOx1 nCoV-19/administración & dosificación , Proteínas de la Nucleocápside de Coronavirus/inmunología , COVID-19/prevención & control , COVID-19/inmunología , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/efectos adversos , Vacunas contra la COVID-19/administración & dosificación , Inmunización Secundaria , Inmunogenicidad Vacunal , Inmunoglobulina G/sangre , Glicoproteína de la Espiga del Coronavirus/inmunología , Vacunación/efectos adversosRESUMEN
OBJECTIVE: To estimate original wild-type BNT162b2 effectiveness against symptomatic Omicron infection among children 5-11 years of age. METHODS: This prospective test-negative, case-control study was conducted in Toledo, southern Brazil, from June 2022 to July 2023. Patients were included if they were aged 5-11 years, sought care for acute respiratory symptoms in the public health system, and were tested for SARS-CoV-2 using reverse transcription polymerase chain reaction. In the primary analysis, we determined the effectiveness of two doses of original wild-type BNT162b2 against symptomatic COVID-19. The reference exposure group was the unvaccinated. RESULTS: A total of 757 children were enrolled; of these, 461 (25 cases; 436 controls) were included in the primary analysis. Mean age was 7.4 years, 49.7 % were female, 34.6 % were obese, and 14.1 % had chronic pulmonary disease. Omicron accounted for 100 % of all identified SARS-CoV-2 variants with BA.5, BQ.1, and XBB.1 accounting for 35.7 %, 21.4 % and 21.4 %, respectively. The adjusted estimate of two-dose vaccine effectiveness against symptomatic Omicron was 3.1 % (95 % CI, -133.7 % to 61.8 %) after a median time between the second dose and the beginning of COVID-19 symptoms of 192.5 days (interquartile range, 99 to 242 days). CONCLUSION: In this study with children 5-11 years of age, a two dose-schedule of original wild-type BNT162b2 was not associated with a significant protection against symptomatic Omicron infection after a median time between the second dose and the beginning of COVID-19 symptoms of 192 days, although the study may have been underpowered to detect a clinically important difference. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov number, NCT05403307 (https://classic. CLINICALTRIALS: gov/ct2/show/NCT05403307).
Asunto(s)
Vacuna BNT162 , COVID-19 , SARS-CoV-2 , Eficacia de las Vacunas , Humanos , COVID-19/prevención & control , COVID-19/inmunología , COVID-19/epidemiología , Femenino , Masculino , Vacuna BNT162/administración & dosificación , Vacuna BNT162/inmunología , SARS-CoV-2/inmunología , SARS-CoV-2/fisiología , Preescolar , Niño , Estudios Prospectivos , Brasil/epidemiología , Estudios de Casos y ControlesRESUMEN
Introduction: Given the limited number of patients in Latin America who have received a booster dose against the COVID-19, it remains crucial to comprehend the effectiveness of different vaccine combinations as boosters in real-world scenarios. This study aimed to assess the real-life efficacy of seven different vaccine schemes against COVID-19, including BNT162b2, ChAdOx1-S, Gam-COVID-Vac, and CoronaVac as primary schemes with either BNT162b2 or ChAdOx1-S as booster vaccines. Methods: In this multicentric longitudinal observational study, participants from Mexico and Argentina were followed for infection and SARS-CoV-2 Spike 1-2 IgG antibodies during their primary vaccination course and for 185 days after the booster dose. Results: A total of 491 patients were included, and the booster dose led to an overall increase in the humoral response for all groups. Patients who received BNT162b2 exhibited the highest antibody levels after the third dose, while those with primary Gam-COVID-Vac maintained a higher level of antibodies after six months. Infection both before vaccination and after the booster dose, and Gam-COVIDVac + BNT162b2 combination correlated with higher antibody titers. Discussion: The sole predictor of infection in the six-month follow-up was a prior COVID-19 infection before the vaccination scheme, which decreased the risk of infection, and all booster vaccine combinations conveyed the same amount of protection.
Asunto(s)
Anticuerpos Antivirales , Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , Inmunización Secundaria , SARS-CoV-2 , Humanos , Argentina , COVID-19/prevención & control , COVID-19/inmunología , Masculino , Femenino , SARS-CoV-2/inmunología , Persona de Mediana Edad , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/inmunología , México , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/administración & dosificación , Adulto , Vacuna BNT162/inmunología , Vacuna BNT162/administración & dosificación , Estudios de Seguimiento , Anciano , Estudios Longitudinales , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Eficacia de las Vacunas , ChAdOx1 nCoV-19/inmunología , Vacunas SintéticasRESUMEN
Booster doses of the SARS-CoV-2 vaccine have been recommended to improve and prolong immunity, address waning immunity over time, and contribute to the control of the COVID-19 pandemic. A heterologous booster vaccine strategy may offer advantages over a homologous approach. To compare the immunogenicity of two doses of BNT162b2 mRNA COVID-19 vaccine with a ChAdOx1-S booster dose, immunoglobulin G (IgG) anti-spike (anti-S) and anti-nucleocapsid (anti-N) antibody titers (Ab) were compared over 1 year and post-booster vaccination. Results showed that, at 3- to 9-month assessments in vaccinated subjects, an-ti-N Ab were undetectable in participants with no history of COVID-19. In contrast, anti-S Ab measurements were lower than those with COVID-19, and a decrease was observed during the 9 months of observation. After booster vaccination, no differences were found in anti-S between participants who reported a history of COVID-19 and those who did not. Anti-S levels were higher after booster vaccination measurement vs. at 9 months in participants with COVID-19 and without COVID-19, i.e., independent of an infection history. Vaccine administration elicited a response of higher anti-S IgG levels in those infected before vaccination, although levels decreased during the first nine months. IgG anti-N titers were higher in participants with a history of declared infection and who were asymptomatic. The ChAdOx1-S booster increased anti-S Ab levels in participants regardless of whether they had been infected or not to a significantly higher value than with the first two vaccines. These findings underscore the importance of booster vaccination in eliciting a robust and sustained immune response against COVID-19, regardless of the prior infection status.
Asunto(s)
Anticuerpos Antivirales , Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , Inmunización Secundaria , Inmunogenicidad Vacunal , Inmunoglobulina G , Personal Militar , SARS-CoV-2 , Humanos , Vacuna BNT162/inmunología , Vacuna BNT162/administración & dosificación , COVID-19/prevención & control , COVID-19/inmunología , Anticuerpos Antivirales/sangre , Anticuerpos Antivirales/inmunología , Masculino , SARS-CoV-2/inmunología , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/administración & dosificación , Adulto , México , Femenino , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Glicoproteína de la Espiga del Coronavirus/inmunología , ChAdOx1 nCoV-19/inmunología , ChAdOx1 nCoV-19/administración & dosificación , Adulto Joven , Vacunación , Persona de Mediana EdadAsunto(s)
Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , Inmunización Secundaria , SARS-CoV-2 , Humanos , Vacuna BNT162/administración & dosificación , COVID-19/virología , SARS-CoV-2/genética , Vacunas contra la COVID-19/inmunología , Anticuerpos Antivirales/sangre , Adulto , Anticuerpos Neutralizantes/sangre , Anticuerpos Neutralizantes/inmunologíaRESUMEN
Inactivated COVID-19 vaccines data in immunocompromised individuals are scarce. This trial assessed the immunogenicity of two CoronaVac doses and additional BNT162b2 mRNA vaccine doses in immunocompromised (IC) and immunocompetent (H) individuals. Adults with solid organ transplant (SOT), hematopoietic stem cell transplant, cancer, inborn immunity errors or rheumatic diseases were included in the IC group. Immunocompetent adults were used as control group for comparison. Participants received two CoronaVac doses within a 28-day interval. IC received two additional BNT162b2 doses and H received a third BNT162b2 dose (booster). Blood samples were collected at baseline, 28 days after each dose, pre-booster and at the trial end. We used three serological tests to detect antibodies to SARS-CoV-2 nucleocapsid (N), trimeric spike (S), and receptor binding domain (RBD). Outcomes included seroconversion rates (SCR), geometric mean titers (GMT) and GMT ratio (GMTR). A total of 241 IC and 100 H adults participated in the study. After two CoronaVac doses, IC had lower SCR than H: anti-N, 33.3% vs 79%; anti-S, 33.8% vs 86%, and anti-RBD, 48.5% vs 85%, respectively. IC also showed lower GMT than H: anti-N, 2.3 vs 15.1; anti-S, 58.8 vs 213.2 BAU/mL; and anti-RBD, 22.4 vs 168.0 U/mL, respectively. After the 3rd and 4th BNT162b2 doses, IC had significant anti-S and anti-RBD seroconversion, but still lower than H after the 3rd dose. After boosting, GMT increased in IC, but remained lower than in the H group. CoronaVac two-dose schedule immunogenicity was lower in IC than in H. BNT162b2 heterologous booster enhanced immune response in both groups.
Asunto(s)
Anticuerpos Antivirales , Vacuna BNT162 , Vacunas contra la COVID-19 , COVID-19 , Huésped Inmunocomprometido , Inmunogenicidad Vacunal , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven , Anticuerpos Antivirales/sangre , Vacuna BNT162/inmunología , Vacuna BNT162/administración & dosificación , COVID-19/prevención & control , COVID-19/inmunología , Vacunas contra la COVID-19/inmunología , Vacunas contra la COVID-19/administración & dosificación , Inmunización Secundaria , Inmunocompetencia/inmunología , Huésped Inmunocomprometido/inmunología , Vacunas de Productos Inactivados/inmunología , Vacunas de Productos Inactivados/administración & dosificaciónRESUMEN
A TECNOLOGIA: Condição clínica: A Covid-19 é uma doença infecciosa causada pelo coronavírus 2 (SARS-CoV2), transmitido principalmente por meio de gotículas e aerossóis respiratórios de pessoa a pessoa. A infecção pode ser disseminada tanto por indivíduos assintomáticos quanto sintomáticos, e os sintomas podem aparecer de dois a 14 dias após a exposição ao vírus. A apresentação clínica da doença Covid-19 é variada. Os sintomas incluem febre, calafrio, tosse, dificuldade respiratória, fadiga, dores musculares, dor de cabeça, perda de paladar e olfato, dor de garganta, congestão nasal e sintomas gastrointestinais. Aproximadamente 5% dos pacientes com Covid-19 e 20% daqueles já hospitalizados apresentam um agravamento da doença, com necessidade de cuidados médicos intensivos. Em 11 de março de 2020, Organização Mundial de Saúde (OMS) declarou status de pandemia da Covid-196. Até o dia 25 de novembro de 2022, foram contabilizados 636.440.663 casos confirmados e 6.606.624 mortes7 pela doença no mundo. No Brasil, foram contabilizados 35.007.209 casos e 688.920 mortes até 19 de novembro de 2022. Após quase três anos de pandemia, o número de mortes devido à doença diminuiu, mesmo com ondas periódicas de aumento de casos que são observadas no mundo. Isso se deve, principalmente, ao avanço da vacinação. Até 23 de novembro de 2022, foram aplicadas, globalmente, um total de 12.959.275.260 de doses de vacina. No entanto, a pandemia de Covid-19 continua sendo um desafio de saúde global contínuo devido ao surgimento de múltiplas variantes do vírus SARS-CoV2. Destaca-se a rápida disseminação global da variante de preocupação ômicron (B.1.1.529, também referida como sublinhagem BA.1) e, mais recentemente, a predominância das sublinhagens ômicron BA.4 e BA.5 (referida como BA.4/BA.5 devido à estrutura similar de suas glicoproteínas spike). Diante da transmissão generalizada em todo o mundo, a OMS criou uma subcategoria de rastreamento, nomeada como sublinhagens de preocupação da variante ômicron. Dados de ensaios clínicos e de estudos de mundo real indicam uma diminuição da proteção após esquema vacinal primário e das doses de reforço ao longo do tempo, além de uma redução da eficácia contra variantes das vacinas originais disponíveis para prevenção da Covid-19. Assim, após o reconhecimento de que a variante ômicron se tornou a cepa circulante globalmente dominante em 2022, os fabricantes rapidamente passaram a desenvolver vacinas de segunda geração, chamadas de bivalentes ou adaptadas. Essas vacinas contêm o código do vírus SARS-CoV-2 original em associação com o código das variantes ômicron, com o objetivo de aumentar a eficácia para a prevenção da Covid-19. DESCRIÇÃO DA TECNOLOGIA: Os laboratórios Pfizer e Moderna desenvolveram e lançaram vacinas bivalentes formuladas com RNA mensageiro (mRNA) que codifica a proteína spike da cepa original do vírus SARS-CoV-2 e o mRNA da variante ômicron (BA.1 ou BA.4/BA.5) do vírus (Quadro 1). O mRNA da cepa original é utilizado para oferecer ampla proteção contra a Covid-19 enquanto o mRNA da ômicron é utilizado para melhorar a proteção contra essa variante. PANORAMA DE DESENVOLVIMENTO: Os ensaios clínicos com o uso das vacinas bivalentes para a profilaxia da Covid-19 foram identificados, inicialmente, na base de pesquisa clínica clinicaltrials.gov. Foram incluídos ensaios clínicos de fases 2, 3 e 4, em andamento ou completos, com o uso das tecnologias para a prevenção da Covid19. Além disso, foram consultadas as bases eletrônicas MEDLINE (via PubMed), EMBASE (via Periódicos Capes) e o Cortellis da Clarivate Analytics para buscar os resultados dos ensaios clínicos. As estratégias de busca foram elaboradas com os termos relacionados à doença e à tecnologia, assim como seus sinônimos e códigos de pesquisa. Todas as buscas foram realizadas em 09 de novembro de 2022. CONSIDERAÇÕES FINAIS: Diante do cenário de disseminação das principais variantes de preocupação estão em desenvolvimento no momento ensaios clínicos com vacinas de diferentes variantes do vírus SARSCoV-2, sozinhas ou associadas à cepa original. As vacinas bivalentes mais adiantadas no seu desenvolvimento são as vacinas dos laboratórios farmacêuticos Pfizer e Moderna, as quais contêm tanto o código da cepa original quanto da variante ômicron BA.1 ou da variante ômicron BA.4/BA.5. Essas vacinas bivalentes já têm aprovação de uso emergencial nas agências sanitárias internacionais e já estão sendo utilizadas como dose de reforço nos respectivos países. No Brasil, ambas as vacinas bivalentes do laboratório Pfizer receberam autorização de uso emergencial pela Anvisa no final do mês de novembro de 2022. Essa aprovação visa ampliar a cobertura vacinal da população como uma ferramenta atualizada de resposta às variantes emergentes, uma vez que dados de mundo real indicam que, na presença da ômicron, a efetividade da dose inicial de reforço com a vacina Comirnaty® monovalente é mais baixa e desaparece mais rapidamente. As evidências indicam que as vacinas bivalentes podem ser utilizadas na população de modo seguro, além de produzir níveis superiores de títulos de anticorpos neutralizantes para as variantes de preocupação mais prevalentes no atual cenário. Os resultados preliminares dos ensaios clínicos mostram que as vacinas bivalentes apresentaram perfis de segurança e reatogenicidade semelhantes àqueles da vacina monovalente, já utilizada em grande escala. As reações adversas comuns foram leves (como dor e inchaço no local de injeção, fadiga, febre e dores de cabeça e nas articulações), sem ocorrência de eventos adversos graves ou miocardite. Quanto à eficácia, os dados de imunogenicidade indicam uma maior neutralização para a variante ômicron BA.1 e BA.4/BA.5. Para dirimir as incertezas existentes e obter dados mais robustos sobre a imunogenicidade e segurança dessas tecnologias, os laboratórios continuarão conduzindo os estudos clínicos com ambas as cepas variantes.
Asunto(s)
Humanos , Vacunas Combinadas/administración & dosificación , SARS-CoV-2/efectos de los fármacos , COVID-19/prevención & control , Vacuna BNT162/administración & dosificación , Vacuna nCoV-2019 mRNA-1273/administración & dosificación , Brasil , Eficacia , Análisis Costo-Beneficio , Proyectos de Desarrollo Tecnológico e InnovaciónRESUMEN
BACKGROUND: The BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) has been authorized for use in children 5 to 11 years of age and adolescents 12 to 17 years of age but in different antigen doses. METHODS: We assessed the real-world effectiveness of the BNT162b2 vaccine against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among children and adolescents in Qatar. To compare the incidence of SARS-CoV-2 infection in the national cohort of vaccinated participants with the incidence in the national cohort of unvaccinated participants, we conducted three matched, retrospective, target-trial, cohort studies - one assessing data obtained from children 5 to 11 years of age after the B.1.1.529 (omicron) variant became prevalent and two assessing data from adolescents 12 to 17 years of age before the emergence of the omicron variant (pre-omicron study) and after the omicron variant became prevalent. Associations were estimated with the use of Cox proportional-hazards regression models. RESULTS: Among children, the overall effectiveness of the 10-µg primary vaccine series against infection with the omicron variant was 25.7% (95% confidence interval [CI], 10.0 to 38.6). Effectiveness was highest (49.6%; 95% CI, 28.5 to 64.5) right after receipt of the second dose but waned rapidly thereafter and was negligible after 3 months. Effectiveness was 46.3% (95% CI, 21.5 to 63.3) among children 5 to 7 years of age and 16.6% (95% CI, -4.2 to 33.2) among those 8 to 11 years of age. Among adolescents, the overall effectiveness of the 30-µg primary vaccine series against infection with the omicron variant was 30.6% (95% CI, 26.9 to 34.1), but many adolescents had been vaccinated months earlier. Effectiveness waned over time since receipt of the second dose. Effectiveness was 35.6% (95% CI, 31.2 to 39.6) among adolescents 12 to 14 years of age and 20.9% (95% CI, 13.8 to 27.4) among those 15 to 17 years of age. In the pre-omicron study, the overall effectiveness of the 30-µg primary vaccine series against SARS-CoV-2 infection among adolescents was 87.6% (95% CI, 84.0 to 90.4) and waned relatively slowly after receipt of the second dose. CONCLUSIONS: Vaccination in children was associated with modest, rapidly waning protection against omicron infection. Vaccination in adolescents was associated with stronger, more durable protection, perhaps because of the larger antigen dose. (Funded by Weill Cornell Medicine-Qatar and others.).
Asunto(s)
Vacuna BNT162 , COVID-19 , Eficacia de las Vacunas , Adolescente , Niño , Humanos , Vacuna BNT162/administración & dosificación , Vacuna BNT162/uso terapéutico , COVID-19/epidemiología , COVID-19/prevención & control , Vacunas contra la COVID-19/administración & dosificación , Vacunas contra la COVID-19/uso terapéutico , Qatar/epidemiología , Estudios Retrospectivos , SARS-CoV-2 , Preescolar , Eficacia de las Vacunas/estadística & datos numéricosRESUMEN
BACKGROUND: By July 14, 2021, 81·3 % of adults (aged ≥18 years) in Chile had received a first SARS-CoV-2 vaccine and 72·3% had received a second SARS-CoV-2 vaccine, with the majority of people given Sinovac's inactivated CoronaVac vaccine (75·3% of vaccines dispensed) or Pfizer-BioNTech's mRNA BNT162b2 vaccine (20·9% of vaccines dispensed). Due to the absence of simultaneous real-world data for these vaccines, we aimed to compare SARS-CoV-2 IgG positivity between vaccines using a dynamic national monitoring strategy. METHODS: From March 12, 2021, 28 testing stations for SARS-CoV-2 IgG detection were installed in hotspots based on cellular-phone mobility tracking within the most populated cities in Chile. Individuals voluntarily approaching the testing stations were invited to do a lateral flow test by finger prick and respond to a questionnaire on sociodemographic characteristics, vaccination status (including type of vaccine if one was received), variables associated with SARS-CoV-2 exposure, and comorbidities. We compared the proportion of individuals testing positive for anti-SARS-CoV-2 IgG across sites by week since vaccination between recipients of CoronaVac and BNT162b2. Unvaccinated participants served as a control population and were matched to vaccinated individuals on the basis of date of presentation to the testing station, gender, and age group. Individuals were excluded from the analysis if they were younger than 18 years, had no declared gender, had an invalid IgG test result, had previously tested positive for SARS-CoV-2 infection on PCR, could not recall their vaccination status, or had been immunised against COVID-19 with vaccines other than CoronaVac or BNT162b2. Here, we report data collected up to July 2, 2021. FINDINGS: Of 64 813 individuals enrolled, 56 261 were included in the final analysis, of whom 33 533 (59·6%) had received at least one dose of the CoronaVac vaccine, 8947 (15·9%) had received at least one dose of the BNT162b2 vaccine, and 13 781 (24·5%) had not received a vaccine. SARS-CoV-2 IgG positivity during week 4 after the first dose of CoronaVac was 28·1% (95% CI 25·0-31·2; 220 of 783 individuals), reaching a peak of 77·4% (75·5-79·3; 1473 of 1902 individuals) during week 3 after the second dose. SARS-CoV-2 IgG positivity during week 4 after the first dose of the BNT162b2 vaccine was 79·4% (75·7-83·1; 367 of 462 individuals), increasing to 96·5% (94·9-98·1; 497 of 515 individuals) during week 3 after the second dose and remaining above 92% until the end of the study. For unvaccinated individuals, IgG seropositivity ranged from 6·0% (4·4-7·6; 49 of 810 individuals) to 18·7% (12·5-24·9; 28 of 150 individuals) during the 5 month period. Regression analyses showed that IgG seropositivity was significantly lower in men than women and in people with diabetes or chronic diseases for CoronaVac vaccine recipients (p<0·0001), and for individuals aged 60 years and older compared with people aged 18-39 years for both vaccines (p<0·0001), 3-16 weeks after the second dose. INTERPRETATION: IgG seropositivity was lower after CoronaVac than after BNT162b2 and declined over time since vaccination for CoronaVac recipients but not BNT162b2 recipients. Prolonged IgG monitoring will allow further evaluation of seropositivity overtime, providing data, in conjunction with effectiveness studies, for possible future re-assessment of vaccination strategies. FUNDING: Instituto Sistemas Complejos de Ingeniería and Ministerio de Salud Chile. TRANSLATION: For the Spanish translation of the abstract see Supplementary Materials section.