New Delhi: The early-stage human trial data has revealed that the Covid-19 vaccine candidate developed by AstraZeneca and Oxford University is safe and induces immune response.
The preliminary results of the phase 1-2 trial, published in The Lancet journal, involved 1,107 healthy adults, and found that the vaccine induced an immune response both via antibodies and the T-cells of the immune system up to day 56 of the ongoing trial.
“The Phase I/II data for our Coronavirus vaccine shows that the vaccine did not lead to any unexpected reactions and had a similar safety profile to previous vaccines of this type,” said Andrew Pollard, Chief investigator of the Oxford Vaccine Trial at Oxford University.
If a vaccine clears phase III human trials, it is ready to be approved for public use.
Evidence before this study
Accirding to Lancet journal, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was identiñed as the causative agent of COVID-19 in January, 2020. There are currently no licensed vaccines to prevent COVID-19. ChAdoxi nCoV-19 has previously been reported to be immunogenic and protective against pneumonia in a rhesus macaque challenge model. We searched PubMed for research articles published between database inception and July 6, 2020, using the terms “SARS-CoV-2”, “vaccine”, “linical trial”, and “phase”. No language restrictions were applied. We identifed one published clinical trial, describing a trial done in China of an adenovirus-5-vectored vaccine against SARS-CoV-2, usinga single dose at three different dose levels. The vaccine was tolerated, with reactogenicity increased at the highest dose. Antibodies, neutralising antibodies in a proportion of vaccinees, and cellular responses were induced. A further clinical trial, which was done in the USA, has been reported on medRxiv. The vaccine was a lipid nanoparticle-formulated, nucleoside-modified, mRNA vaccine that encodes trimerised SARS-CoV-2 spike glycoprotein receptor binding domain administered at one or two doses of three dose levels. The vaccine was tolerated, with reactogenicity increased at the highest dose. Antibodies and neutralizing antibodies were induced in a dose-dependent manner and increased after a second dose.
Added value of this study
We report the results of the first clinical study of ChAdOx1nCoV-19 (AZD1222). The vaccine was safe and tolerated, with reduced reactogenicity when paracetamol was used prophylactically for the first 24 h after vaccination. Reactogenicity was reduced after a second dose. Humoral responses to SARS-CoV-2 spike protein peaked by day 28 post 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 was present in all participants studied.
Implications of all the available evidence
A vaccine against SARS-CoV-2 could be used to prevent infection, disease, and death in the global population, with high-risk populations such as hospital workers and older adults (eg, >65 years of age) prioritised to receive vaccination.
The immune correlates of protection against SARS-CoV-2 have not yet been tetermined. Immunisation with ChAdOx1 nCoV-19 results in rapid induction of both humoral and cellular immune responses against SARS-CoV-2, with increased responses after a second dose. Further cinical studies, including in older adults, should be done with this vaccine.
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