Homologous equivalence study of immunogenicity after third dose of Covid-19 vaccine (recombinant) with an interval of six months after the second dose, comparing the interval of eight and 12 weeks between the first two doses

In response to the coronavirus disease 2019 (Covid-19) pandemic, Brazil authorised the Astra Zeneca/Fiocruz vaccine in January 2021. As the Delta variant emerged in May 2021, interval between vaccine doses was adjusted. By September 2021, the Brazilian National Immunisation Program recommended a boo...

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Published in:Memórias do Instituto Oswaldo Cruz 2024-01, Vol.119, p.e240094
Main Authors: Vianna, Clarice Monteiro, da Silva e Sá, Gloria Regina, Seid, Maria Vitória Hadland, Camacho, Luiz Antonio Bastos, Xavier, Janaína Reis, da Gama, Vitor Cardoso, de Castro, Thalita da Matta, dos Santos, Ewerton Alves Portela, de Almeida, Camila Dias, Cruz, Robson Leite de Souza, Siqueira, Marilda, Maia, Maria de Lourdes de Sousa, Ferroco, Clara Lucy de Vasconcellos, de Araújo, Mia Ferreira, Tort, Luis Fernando López, Caetano, Braulia Costa
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Language:English
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Summary:In response to the coronavirus disease 2019 (Covid-19) pandemic, Brazil authorised the Astra Zeneca/Fiocruz vaccine in January 2021. As the Delta variant emerged in May 2021, interval between vaccine doses was adjusted. By September 2021, the Brazilian National Immunisation Program recommended a booster dose for individuals over 70, and later expanded the recommendation to all adults.BACKGROUNDIn response to the coronavirus disease 2019 (Covid-19) pandemic, Brazil authorised the Astra Zeneca/Fiocruz vaccine in January 2021. As the Delta variant emerged in May 2021, interval between vaccine doses was adjusted. By September 2021, the Brazilian National Immunisation Program recommended a booster dose for individuals over 70, and later expanded the recommendation to all adults.Assess the equivalence of IgG antibody response against the Covid-19 S protein before and approximately 28 days after the third dose of a Covid-19 recombinant vaccine. Two groups received initial two doses with intervals of eight and 12 weeks.OBJECTIVESAssess the equivalence of IgG antibody response against the Covid-19 S protein before and approximately 28 days after the third dose of a Covid-19 recombinant vaccine. Two groups received initial two doses with intervals of eight and 12 weeks.This is a phase IV clinical study, uncontrolled, non-randomised. The study proposes calculating the ratio of geometric means titres (GMT) 28 days after the third dose, with a target ratio of confidence interval (CI) between 0.77 and 1.3.METHODSThis is a phase IV clinical study, uncontrolled, non-randomised. The study proposes calculating the ratio of geometric means titres (GMT) 28 days after the third dose, with a target ratio of confidence interval (CI) between 0.77 and 1.3.In the primary endpoint, there was no equivalence between the eight- and 12-week intervals with a slight variation favouring the eight-week group. Post-third dose, both groups showed increases titres at 28 days, three months, six months and 12 months. Both groups responded similarly to Delta and Omicron BA.1, with a more significant increase for Delta.FINDINGSIn the primary endpoint, there was no equivalence between the eight- and 12-week intervals with a slight variation favouring the eight-week group. Post-third dose, both groups showed increases titres at 28 days, three months, six months and 12 months. Both groups responded similarly to Delta and Omicron BA.1, with a more significant increase for Delta.The study showed strong
ISSN:0074-0276
1678-8060
1678-8060
DOI:10.1590/0074-02760240094