Oxford Covid vaccine safe, no major side effects: Study

Ten participants were studied separately, receiving a booster dose of ChAdOx1 28 days after the first dose. (Representative image)

The Oxford/AstraZeneca Covid-19 vaccine candidate was found to be safe, without major side effects, and has encouraging immunogenic — SARS CoV-2 fighting —effect in Phase 1 and 2 clinical trials in the UK, fuelling hopes of vaccine-driven control over the spread of the virus. Pending results of Phase 3 clinical trials — in which immunogenicity and safety will be observed at a much larger scale — the Oxford vaccine has now emerged as a first among equals in a race that features candidates like CanSino’s and Moderna’s vaccine candidates.

The Oxford trials were carried out at five sites in the UK, and involved 1,077 healthy, adult participants; 543 were administered the vaccine candidate, named ChAdOx1 nCoV-19, and 534 were given the meningococcal vaccine as a control. Ten participants were studied separately, receiving a booster dose of ChAdOx1 28 days after the first dose.

Findings of the study, published in The Lancet, detail minor side effects like localised pain, feeling feverish, chills, muscle ache, and headache. The study notes that while fatigue and headache were the most commonly reported systemic side effects, many of the side effects could be controlled with prophylactic use of paracetamol.

The vaccine candidate, which involves injection of viral genetic material packed in a chimpanzee adenovirus vector to express the SARS CoV-2’s spike proteins, induced creation of spike-protein specific T-lymphocytes (which attack infected cells and are part of immune system memory which helps in curbing later infections by the same pathogen) and neutralising antibodies (a pathogen-specific response). The antibody response rose by the 28th day, and was found to be boosted in the group that received the second dose, showing neutralising activity even on the 56th day in a particular type of test.

Given the spike-specific T-lymphocyte formation, there is the hope that the vaccine could give protection for an extended period of time, even if the antibodies don’t sustain — studies in Germany and China have reported antibodies waning within months of infection. However, more research will be needed to confirm this, and if the level of immunogenicity can prove effective against the SARS CoV-2 virus in the long run.

The Lancet also published the results of the Phase 2 trials of CanSino’s vaccine candidate among 508 participants in Wuhan, China. This vaccine candidate uses a human adenovirus vector to deliver the viral genetic material, which makes it potentially susceptible to immune system response against the vector itself. The study reports that the vaccine candidate was safe, with no major side effect, and that it induced significant immunogenic effect for both the doses that were studied.