Disclosing the study details, reputed medical journal Lancet on Monday said both groups used an adenoviral vector, and both report the vaccine achieving responses to the SARS-CoV-2 spike glycoprotein, which mediates coronavirus' entry into host cells. While there were concerns on whether the immunity would last in the case of COVID-19 vacccines under development, the results said T-cells, which directly target and kill infected cells, were induced by the vaccine.
The half way stage results are good news, as more than 70 per cent of that vaccines that enter the final hurdle of Phase III human trials succeed to hit the markets.
The Oxford vaccine in Phase II/III was found above 90 per cent effective in the first two phases of human trials. It was tested between April 23 and May 21, in 1,077 participants at five hospitals in the UK.
Only mild reactions were seen in the participants like pain, feeling feverish, chills, muscle ache, headache, and malaise. Neutralising antibody responses against SARS-CoV-2 were detected in 32 (91 per cent) of 35 participants after a single dose and in all participants (100 per cent) of another group of 35.
"ChAdOx1 nCoV-19 showed an acceptable safety profile, and homologous boosting increased antibody responses. These results, together with the induction of both humoral and cellular immune responses, support large-scale evaluation of this candidate vaccine in an ongoing Phase III programme," said the researchers.
They said the vaccine was safe and tolerated, with reduced adverse reactions when paracetamol was used prophylactically for the first 24 hours after vaccination. Reactions were reduced after a second dose. Humoral responses to SARS-CoV-2 spike protein peaked by Day 28 after prime and cellular responses were induced in all participants by Day 14. Neutralising antibodies were induced in all participants after a second vaccine dose. After two doses, potent cellular and humoral immunogenicity, or ability to develop immune response was present in all participants. A small, non-randomly selected second-dose boosted subset showed strong neutralising responses, and few mild adverse events. Importantly, T-cell responses were induced in all participants.
In the case of the vaccine by China's CanSino Biologics, adverse events such as fever, fatigue, headache, or local site pain occurred by Day 28 in 294 (77 per cent) of 382 vaccinees and 61 (48 per cent) of 126 placebo (faking drug) recipients.
Male sex was associated with lower occurrence of fever post-vaccination. No serious adverse events occurred. Neutralising antibodies were generated in about 85 per cent and more than 90 per cent had T-cell responses.
"The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety. Overall, the results of both trials are broadly similar and promising, notwithstanding differences in the vector, in the geographical locations of the populations studied, and the neutralisation assays used", observed Lancet.
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