Persistence of immunogenicity after seven COVID-19 vaccines given as third dose boosters following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK: three month analyses of the COV-BOOST trial.
Liu X., Munro APS., Feng S., Janani L., Aley PK., Babbage G., Baxter D., Bula M., Cathie K., Chatterjee K., Dejnirattisai W., Dodd K., Enever Y., Qureshi E., Goodman AL., Green CA., Harndahl L., Haughney J., Hicks A., van der Klaauw AA., Kwok J., Libri V., Llewelyn MJ., McGregor AC., Minassian AM., Moore P., Mughal M., Mujadidi YF., Holliday K., Osanlou O., Osanlou R., Owens DR., Pacurar M., Palfreeman A., Pan D., Rampling T., Regan K., Saich S., Serafimova T., Saralaya D., Screaton GR., Sharma S., Sheridan R., Sturdy A., Supasa P., Thomson EC., Todd S., Twelves C., Read RC., Charlton S., Hallis B., Ramsay M., Andrews N., Lambe T., Nguyen-Van-Tam JS., Cornelius V., Snape MD., Faust SN., COV-BOOST study group None.
ObjectivesTo evaluate the persistence of immunogenicity three months after third dose boosters.MethodsCOV-BOOST is a multicentre, randomised, controlled, phase 2 trial of seven COVID-19 vaccines used as a third booster dose. The analysis was conducted using all randomised participants who were SARS-CoV-2 naïve during the study.ResultsAmong the 2883 participants randomised, there were 2422 SARS-CoV-2 naïve participants until D84 visit included in the analysis with median age of 70 (IQR: 30-94) years. In the participants who had two initial doses of ChAd, schedules using mRNA vaccines as third dose have the highest anti-spike IgG at D84 (e.g. geometric mean concentration of 8674 ELU/ml (95% CI: 7461-10085) following ChAd/ChAd/BNT). However, in people who had two initial doses of BNT there was no significant difference at D84 in people given ChAd versus BNT (geometric mean ratio (GMR) of 0.95 (95%CI: 0.78, 1.15). Also, people given Ad26.COV2.S (Janssen; hereafter referred to as Ad26) as a third dose had significantly higher anti-spike IgG at D84 than BNT (GMR of 1.20, 95%CI: 1.01,1.43). Responses at D84 between people who received BNT (15 μg) or BNT (30 μg) after ChAd/ChAd or BNT/BNT were similar, with anti-spike IgG GMRs of half-BNT (15 μg) versus BNT (30 μg) ranging between 0.74-0.86. The decay rate of cellular responses were similar between all the vaccine schedules and doses.Conclusions84 days after a third dose of COVID-19 vaccine the decay rates of humoral response were different between vaccines. Adenoviral vector vaccine anti-spike IgG concentration at D84 following BNT/BNT initial doses were higher than for a three dose (BNT/BNT/BNT) schedule. Half dose BNT immune responses were similar to full dose responses. While high antibody tires are desirable in situations of high transmission of new variants of concern, the maintenance of immune responses that confer long-lasting protection against severe disease or death is also of critical importance. Policymakers may also consider adenoviral vector, fractional dose of mRNA, or other non-mRNA vaccines as third doses.