PT  - JOURNAL ARTICLE
AU  - Laura Solforosi
AU  - Harmjan Kuipers
AU  - Sietske K. Rosendahl Huber
AU  - Joan E.M. van der Lubbe
AU  - Liesbeth Dekking
AU  - Dominika N. Czapska-Casey
AU  - Ana Izquierdo Gil
AU  - Miranda R.M. Baert
AU  - Joke Drijver
AU  - Joost Vaneman
AU  - Ella van Huizen
AU  - Ying Choi
AU  - Jessica Vreugdenhil
AU  - Sanne Kroos
AU  - Adriaan H. de Wilde
AU  - Eleni Kourkouta
AU  - Jerome Custers
AU  - Tim J. Dalebout
AU  - Sebenzile K. Myeni
AU  - Marjolein Kikkert
AU  - Eric J. Snijder
AU  - Dan H. Barouch
AU  - Kinga P. Böszörményi
AU  - Marieke A. Stammes
AU  - Ivanela Kondova
AU  - Ernst J. Verschoor
AU  - Babs E. Verstrepen
AU  - Gerrit Koopman
AU  - Petra Mooij
AU  - Willy M.J.M. Bogers
AU  - Marjolein van Heerden
AU  - Leacky Muchene
AU  - Jeroen T.B.M. Tolboom
AU  - Ramon Roozendaal
AU  - Hanneke Schuitemaker
AU  - Frank Wegmann
AU  - Roland C. Zahn
TI  - Immunogenicity and protective efficacy of one- and two-dose regimens of the Ad26.COV2.S COVID-19 vaccine candidate in adult and aged rhesus macaques
AID  - 10.1101/2020.11.17.368258
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2020.11.17.368258
4099  - http://biorxiv.org/content/early/2021/01/04/2020.11.17.368258.short
4100  - http://biorxiv.org/content/early/2021/01/04/2020.11.17.368258.full
AB  - Safe and effective coronavirus disease (COVID)-19 vaccines are urgently needed to control the ongoing pandemic. While single-dose vaccine regimens would provide multiple advantages, two doses may improve the magnitude and durability of immunity and protective efficacy. We assessed one- and two-dose regimens of the Ad26.COV2.S vaccine candidate in adult and aged non-human primates (NHP). A two-dose Ad26.COV2.S regimen induced higher peak binding and neutralizing antibody responses compared to a single dose. In one-dose regimens neutralizing antibody responses were stable for at least 14 weeks, providing an early indication of durability. Ad26.COV2.S induced humoral immunity and Th1 skewed cellular responses in aged NHP that were comparable to adult animals. Importantly, aged Ad26.COV2.S-vaccinated animals challenged 3 months post -dose 1 with a SARS-CoV-2 spike G614 variant showed near complete lower and substantial upper respiratory tract protection for both regimens. These are the first NHP data showing COVID-19 vaccine protection against the SARS-CoV-2 spike G614 variant and support ongoing clinical Ad26.COV2.S development.Summary COVID-19 vaccines are urgently needed and while single-dose vaccines are preferred, two-dose regimens may improve efficacy. We show improved Ad26.COV2.S immunogenicity in non-human primates after a second vaccine dose, while both regimens protected aged animals against SARS-CoV-2 disease.Competing Interest StatementThe authors have declared no competing interest.