In the race for an effective COVID-19 vaccine, July 20 is a big day. Early trials from the University of Oxford and Wuhan were published in The Lancet with both showing efficacy in increasing the presence of antibody responses to SARS-CoV-2.
In the Wuhan trial, healthy adults aged 18 years or older, who were HIV-negative and previous SARS-CoV-2 infection-free, were eligible to participate and randomly assigned to receive the vaccine or a placebo. The randomized, double-blind, placebo-controlled, Phase 2 trial of the adenovirus type-5 (Ad5)-vectored COVID-19 vaccine showed that both doses of the administered vaccine induced significant neutralizing antibody responses to live SARS-CoV-2. No serious adverse reactions were documented.
Commenting on the Oxford and Wuhan trials, Ian Jones, professor of virology, University of Reading, said, “The data from the Phase 1/2 trial of the Oxford vaccine are as good as one could reasonably expect and confirm earlier use of the vector as a general vaccine platform. Trial participants developed the all-important neutralizing antibodies, in most cases after one shot and in all cases after two shots. The outcome was measured in several ways to be sure that one assay did not give an overly generous answer but in fact all the methods agreed. The parallel Chinese study, which uses a human adenovirus instead of the chimpanzee adenovirus, also worked and despite the difference in the “vector” used, can be considered to re-enforce the case for an adenovirus vectored vaccine being a viable option for COVID-19.”
Danny Altmann, British Society for Immunology spokesperson and professor of immunology at Imperial College London, said, “The Beijing approach is based on the backbone of a conventional human, common-cold virus to which some people have pre-existing antibodies and they therefore make a lower response in some people to the vaccine because people have pre-existing antibodies to their vector, so may clear it before it has a chance to work properly. The Oxford approach overcomes this by deriving a chimp adenovirus platform to which humans have not made prior antibodies. While both vaccines raise a T cell response, the frequency of cells stimulated to respond by the Oxford vaccine look substantially higher, which would almost certainly be advantageous. On the other hand, the Oxford approach is based on two injections (“prime-boost”), which would add considerably to logistic demands. Next steps, as the teams confirm, will be to establish durability and protective efficacy of these responses, including in people of different age groups.”
The Chinese team concluded that the results support testing of the vaccine in a Phase 3 effectiveness trial in healthy adults.
Folegatti, et al. (2020). Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial. The Lancet. DOI: https://doi.org/10.1016/ S0140-6736(20)31604-4
Xhu, et al. (2020). Immunogenicity and safety of a recombinant adenovirus type-5-vectored COVID-19 vaccine in healthy adults aged 18 years or older: a randomised, double-blind, placebo controlled, phase 2 trial. The Lancet. DOI: https://doi.org/10.1016/S0140-6736(20)31605-6