Today (06 Apr 2021) Valneva issued a press release about its Covid-19 vaccine.

The vaccine, to be produced in Scotland, is quite different from the currently-available vaccines.  The vaccines we currently use in the UK are very similar to each other.  One type is the mRNA vaccines, in which the genetic programme for the SARS-CoV-2 “spike protein” is smuggled into cells in the form of messenger RNA (mRNA), where the cells treat it like DNA from the cell’s nucleus and manufacture the protein.  The other is a vector vaccine, in which a harmless virus that cannot replicate in the body is injected: it gets into cells, and tells the cell to produce proteins – that’s how viruses work.  But most of their replication machinery is disabled, and the genes for the spike protein have been engineered into the virus, so they produce mRNA which the cell uses to produce the same spike protein.

So both mechanisms end up generating mRNA, which cells use to build the SARS-CoV-2 spike protein; and this protein is then secreted by the cells, where it stimulates the immune system to recognise it as an “antigen”, and to respond to it, so that if the actual virus is ever present, the immune system can immediately recognise and kill it.

The Valneva vaccine is a much more traditional sort of vaccine.  Instead of getting our own cells to manufacture the antigen – the spike protein – the vaccine uses the killed SARS-CoV-2 virus.  The virus first has to be grown in culture – a little like growing yeast for brewing.  It is then killed, mixed with an “adjuvant”, and injected.  The adjuvant stimulates a stronger immune response to the virus than you’d get with the virus alone.

We have yet to see how well this vaccine will work in the real world.  The phase I and II trials data reported tell us that people given the vaccine produced a good immune response (both an antibody response, and cellular immunity); but the phase III trials (that will tell us whether they are less likely to be infected or to get ill) have not yet started.  Given the good results of the initial trials, we can be very hopeful that the phase III trials will also provide good results.

Valneva’s vaccine uses the whole virus, not just the spike protein.  This means that the immune system is likely to create an immune response to other parts of the virus that are not included in the mRNA and vector vaccines currently in use.  We do not yet know whether this will make any difference; but in theory it might, possibly, provide better cross-protection against variant strains, and/or better protection against infection, not just against illness.

As long as the vaccine is effective, any addition to our vaccine armoury will be useful.  We need to get the whole world vaccinated as soon as possible – the more, different vaccines that are available, the less likely it is that shortages of or concerns about one or other of the vaccines will be able to delay the global roll-out of vaccines.

‍