The results from a Phase I/II trial of a vaccine produced at the Jenner Institute, Oxford, indicate that the vaccine appears to be safe and able to generate spike-specific antibodies after 28 days.
The single-dose vaccine is based on a chimpanzee adenovirus and directed at the spike protein of the coronavirus which facilitates receptor binding and entry to host cells.
The study enrolled 1077 healthy adults (median age 35 years) who were randomised to receive either the test vaccine (543) or a meningococcal conjugate vaccine which acted as a control. A sub-group of 10 patients from the COVID-19 vaccine group received a booster dose on day 28.
In the test vaccine group, spike-specific antibodies peaked by day 28 and remained elevated to day 56. Neutralising antibodies were initially detected in only 32 patients after a single dose of the test vaccine but in the sub-group of 10 patients, neutralising antibodies were detected in all 10 patients by day 42. Systemic adverse effects reported in the test vaccine group included fatigue (70%), headache (68%), muscle ache (60%), malaise (61%) and chills (56%). A protocol amendment allowed participants to have access to prophylactic paracetamol which reduced the proportion of those reporting systemic effects.
The authors concluded that these preliminary results indicate that the COVID-19 vaccine is safe and that reactogenicity was reduced by paracetamol. Phase II and III trials that will include a wider group of patients are currently in progress.
Folegatti PM et al. Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2 : a preliminary report of a phase ½, single-blind, randomised controlled trial. Lancet. 2020; (published online July 20.) https://doi.org/10.1016/S0140-6736(20)31604-4