Eurosurv. A third vaccine dose equalises the levels of effectiveness and immunogenicity of heterologous or homologous COVID-19 vaccine regimens, Lyon,

[tetano]

• Nicolas Guibert[SUP]1[/SUP] , Kylian Trepat[SUP]2,3[/SUP] , Bruno Pozzetto[SUP]2,4[/SUP] , Laurence Josset[SUP]2,5,6[/SUP] , Jean-Baptiste Fassier[SUP]1[/SUP] , Omran Allatif[SUP]2[/SUP] , Kahina Saker[SUP]3[/SUP] , Karen Brengel-Pesce[SUP]3[/SUP] , Thierry Walzer[SUP]2,*[/SUP] , Philippe Vanhems[SUP]2,7,*[/SUP] , Sophie Trouillet-Assant[SUP]2,3,*[/SUP] , on behalf of the Lyon-COVID study group[SUP]8[/SUP]

Background

To cope with the persistence of the COVID-19 epidemic and the decrease in antibody levels following vaccination, a third dose of vaccine has been recommended in the general population. However, several vaccine regimens had been used initially for the primary vaccination course, and the heterologous Vaxzevria/Comirnaty regimen had shown better efficacy and immunogenicity than the homologous Comirnaty/Comirnaty regimen.

Aim

We wanted to determine if this benefit was retained after a third dose of an mRNA vaccine.

Methods

We combined an observational epidemiological study of SARS-CoV-2 infections among vaccinated healthcare workers at the University Hospital of Lyon, France, with a prospective cohort study to analyse immunological parameters before and after the third mRNA vaccine dose.

Results

Following the second vaccine dose, heterologous vaccination regimens were more protective against infection than homologous regimens (adjusted hazard ratio (HR) = 1.88; 95% confidence interval (CI): 1.18–3.00; p = 0.008), but this was no longer the case after the third dose (adjusted HR = 0.86; 95% CI: 0.72–1.02; p = 0.082). Receptor-binding domain-specific IgG levels and serum neutralisation capacity against different SARS-CoV-2 variants were higher after the third dose than after the second dose in the homologous regimen group, but not in the heterologous group.

Conclusion

The advantage conferred by heterologous vaccination was lost after the third dose in terms of both protection and immunogenicity. Immunological measurements 1 month after vaccination suggest that heterologous vaccination induces maximal immunity after the second dose, whereas the third dose is required to reach the same level in individuals with a homologous regimen.

https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.15.2200746#html_fulltext