Scientists from the University of Oxford are preparing to produce new versions of the vaccine they developed with AstraZeneca in order to combat new variants of the coronavirus.
The emergence of variants of the SARS-Cov-2 virus, which causes COVID-19, has led to concerns about whether existing vaccines would be effective at producing herd immunity in the population. Initial laboratory tests indicate that the Pfizer-BioNTech vaccine is effective against the B117 variant which emerged in Kent. However, there are concerns that variants which emerged in Brazil and South Africa may be resistant to the vaccines being rolled out worldwide.
Each time a virus infects a cell to produce copies of itself, there is a chance that errors occur in the copying process which produces the genetic material for new viruses. These errors are genetic mutations. According to Dr Amesh A. Adalja from Johns Hopkins University, a new variant is a “version of the virus that has accumulated enough mutations to represent a separate branch on the family tree”.
Most mutations have no effect. However, mutations which occur in the sections of genetic code which determine the structure of spike proteins on the virus’ surface can be hugely consequential. In order to combat a viral infection, specialised white blood cells called B-cells produce antibodies which are complimentary to the structure of the viral spike protein. These antibodies provide immunological memory, helping to fight future infection by this type of virus. If someone is then infected with a variant of that virus with altered spike proteins, their immunological memory will not recognise the new variant.
The Oxford, Moderna and Pfizer vaccines all work by introducing strands of viral mRNA into the cells of a person who receives an injection. That mRNA is then translated by the cell to produce SARS-CoV-2 spike proteins. The body’s immune system then produces antibodies which are complimentary to these spike proteins, which provide immunity against future infection.
Sir John Bell, Regius Professor of Medicine at Oxford, has expressed confidence that the Oxford vaccine can be quickly edited to provide immunity against new variants. This would involve editing the sequence of genetic material which make up the mRNA strands used in COVID vaccines.
The Medicines and Healthcare products Regulatory Agency (MHRA) is in talks with the independent Commission on Human Medicines to determine how modified COVID-19 vaccines should be regulated. Sir Bell suggested that modified vaccines would only need to be tested on a small sample size to ensure that they were effective, instead of the thousands involved in the development of the first vaccine.
A spokesperson for MHRA told The Guardian: “We can say at this stage that it is unlikely that a full new approval process will be needed,” indicating that a modified vaccine could be approved for use quickly. However, they emphasised that “No vaccine will be authorised for supply in the UK unless the expected standards of safety, quality and effectiveness are met.”
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