The preliminary results of the Phase-1/2 clinical trial of the Oxford vaccine shows the vaccine is safe, well-tolerated, and immunogenic. The vaccine induced strong antibody by day 28 and remained high until day 56 in those who received only one dose. All the 10 participants who received the second dose demonstrated elevated antibody responses at day 56. The T cell responses increased in all the participants, peaking after 14 days. The T cell responses did not increase after the second dose.

The preliminary results of the Phase-1/2 clinical trial of the Oxford vaccine (ChAdOx1 nCoV-19) to prevent infection by novel coronavirus has been found safe, well-tolerated, and immunogenic. Safety was assessed over 28 days after vaccination.

The trial conducted on 1,077 healthy adult participants found that the vaccine induced strong antibody by day 28 and remained high until day 56 in those who received only one dose. All the 10 participants who received the second (booster) dose demonstrated elevated antibody responses at day 56. There was rapid induction of both antibody and T cell immune responses against coronavirus.

The T cell responses targeting the spike protein of the virus markedly increased (in the 43 participants studied), peaking after 14 days. The T cell response did not increase with a second (booster) dose of the vaccine, which is consistent with other vaccines of this kind, The Lancet tweeted.

The participants are aged 18-55 years and were enrolled for the trial at five sites in the UK between April 23 and May 21. They were randomly assigned to receive either the candidate vaccine or meningococcal conjugate vaccine (control group). The participants did not know whether they received the candidate vaccine or the meningococcal conjugate vaccine but the people conducting the trial knew who received the candidate vaccine and who did not.

The results were published on July 20 in the journal The Lancet.

Adverse evets both local and systemic were “common” in participants who received the vaccine. These adverse events include pain, feeling feverish, chills, muscle ache, headache, and malaise. The use of use of prophylactic paracetamol reduced the adverse events. No serious adverse events were seen.

Fatigue and headache were the most commonly reported reactions. In all, 70% (340/487) of all participants given the Oxford candidate vaccine reported fatigue, while 68% (331/487) reported headache.

A sub-group study involved 10 of the 1,077 participants who received two doses of the vaccine in a prime-boost strategy. The booster dose (second dose) was administered 28 days after the first dose (prime dose). The antibody and T cell immune responses in this group of 10 participants, who were assigned to the group without any randomisation, were even greater after the second dose was administered.

The researchers found spike-specific T-cell responses peaking on day 14 after the first dose. Anti-spike IgG responses increased by day 28 and were elevated further following the second (booster) dose. Neutralising antibody responses against the virus were detected in 32 (91%) of 35 participants after the first dose when measured in MNA80 and in all the 35 (100%) participants when measured in PRNT50.

“After a booster dose, all participants had neutralising activity (nine of nine in MNA80 at day 42 and ten of ten in Marburg VN on day 56). Neutralising antibody responses correlated strongly with antibody levels measured by ELISA,” they write.

According to the authors, using a booster (second) dose increased the antibody responses. “These results, together with the induction of both humoral and cellular immune responses, support largescale evaluation of this candidate vaccine in an ongoing phase-3 programme,” they write.