Heterologous Gam-COVID-Vac (Sputnik V)/mRNA-1273 (Moderna) vaccination: Author's response.

To the Editor:

We appreciate the observation from the authors Rujittika Mungmunpuntipantip and Viroj Wiwanitkit [1] regarding our publication [2]. Certainly, there is a vast number of factors that may affect immunological parameters from a greater to a lesser extent. We agree this is an important aspect, so the analysis of the immunological parameters assessed in our work has considered the broadly established factors that may have potentially impacted the immune response in our setting. Although elevated anti-S-RBD immunoglobulin (IgG) values after asymptomatic COVID-19 cannot be excluded, both groups of our comparative study would have been affected similarly; therefore, an impact on the conclusions would unlikely be altered. Moreover, the detection of the nucleoprotein IgG antibody to distinguish vaccine-induced seropositivity from natural infection is limited due to its significant decrease after 120 days postinfection period [3]. Consequently, we felt that the analytical approach initially performed in our research was accurate. Finally, the immune response variations according to different boost vaccination schemes observed in our study were also registered in a subset of patients receiving dialysis [4] and confirmed by a recently published study that assessed the humoral response to several vaccination schemes, including the homologous prime-boost vaccination with Gam-COVID-Vac and the heterologous combination with mRNA-1273 (Moderna) vaccine [5].

Transparency declaration

The authors have no conflicts of interest to declare.

Author's contributions

Lucas Amaya, Patricia Bare, Natalia Echegoyen, María Noel Badano, Alicia Lucero, Antonella Martelli, Gabriel H. Garcia, Cristina Videla and Alfredo P. Martínez: revising the letter critically for important intellectual content, final approval of the version to be submitted. Matías J. Pereson, Karin Neukam and Federico A. Di Lello: drafting the letter.