Differential effects of the second SARS-CoV-2 mRNA vaccine dose on T cell immunity in naïve and COVID-19 recovered individuals

Lozano-Ojalvo, Daniel; Camara, Carmen; Lopez-Granados, Eduardo; Nozal, Pilar; Pino-Molina, Lucía del; Bravo-Gallego, Yadira; Paz-Artal, Estela; Pion, Marjorie; Correa-Rocha, Rafael; Ortiz, Alberto; Lopez-Hoyos, Marcos; Iribarren, Marta Erro; Portoles, Jose; Rojo-Portoles, Maria Pilar; Ojeda, Gloria; Cervera, Isabel; Gonzalez-Perez, Maria; Bodega-Mayor, Irene; Montes-Casado, Maria; Portoles, Pilar; Perez-Olmeda, Mayte; Oteo, Jesus; Sanchez-Tarjuelo, Rodrigo; Pothula, Venu; Schwarz, Megan; Brahmachary, Manisha; Tan, Anthony Tanoto; Le Bert, Nina; Berin, Cecilia; Bertoletti, Antonio; Guccione, Ernesto; Ochando, Jordi

The rapid development of mRNA-based vaccines against the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) led to the design of accelerated vaccination schedules that have been extremely effective in naïve individuals. While a two-dose immunization regimen with the BNT162b2 vaccine has been demonstrated to provide a 95% efficacy in naïve individuals, the effects of the second vaccine dose in individuals who have previously recovered from natural SARS-CoV-2 infection has not been investigated in detail. Here we characterize, SARS-CoV-2 spike-specific humoral and cellular immunity in naïve and previously infected individuals during and after two-doses of BNT162b2 vaccination. Our results demonstrate that, while the second dose increases both the humoral and cellular immunity in naïve individuals, COVID-19 recovered individuals reach their peak of immunity after the first dose. These results suggests that a second dose, according to the current standard regimen of vaccination, may be not necessary in individuals previously infected with SARS-CoV-2.