Protection against severe COVID-19 after second booster dose of adapted bivalent (original/Omicron BA.4-5) mRNA vaccine in persons ≥ 60 years, by time since infection, Italy, 12 September to 11 December 2022
Massimo Fabiani, Alberto Mateo‐Urdiales, Chiara Sacco, Emmanouil Alexandros Fotakis, Maria Cristina Rota, Daniele Petrone, Marco Bressi, Martina Del Manso, Andrea Siddu, Giorgio Fedele, Paola Stefanelli, Antonino Bella, Flavia Riccardo, Anna Teresa Palamara, Giovanni Rezza, Silvio Brusaferro, Patrizio Pezzotti, on behalf of the Italian Integrated Surveillance of COVID-19 study group and of the Italian COVID-19 Vaccines Registry group
Abstract
Effectiveness against severe COVID-19 of a second booster dose of the bivalent (original/BA.4-5) mRNA vaccine 7-90 days post-administration, relative to a first booster dose of an mRNA vaccine received ≥ 120 days earlier, was ca 60% both in persons ≥ 60 years never infected and in those infected > 6 months before. Relative effectiveness in those infected 4-6 months earlier indicated no significant additional protection (10%; 95% CI: -44 to 44). A second booster vaccination 6 months after the latest infection may be warranted.