Nuvaxovid (NVX-CoV2373) is the name of the new one. The fifth vaccine against COVID-19 approved by us comes from the laboratories of the US vaccine manufacturer Novavax and four million vaccine doses are expected to arrive in Germany in January.
The vaccination principle of Nuvaxovid differs fundamentally from that of the vector and mRNA vaccines. This is based on a well-established concept, which is also the basis of some flu vaccines: a so-called split vaccine consisting of viral proteins. This type of vaccine is created when viruses created in a laboratory are chemically broken down. Organic solvents or surfactants burst the virus envelope into larger fragments. These are then cleaned and the fragments that are suitable for a vaccination reaction are selected.
Genetically modified split vaccines are relatively new
For the COVID-19 vaccine However, the company did not disassemble SARS-CoV-2 viruses, but genetically modified baculoviruses to produce the spike protein of the coronavirus. Baculoviruses are DNA viruses that only infect invertebrates – preferably moths. The vaccine developers incorporated the gene of the SARS-CoV-2 spike virus into these baculoviruses and then grew these viruses in cell cultures based on moth cells. The spike protein has also been modified by three mutations in such a way that it is later better processed by the immune system as a vaccine and is also protected from degradation by enzymes. But, like all other approved vaccines against COVID-19, it is based on the wild-type variant of the virus.
The cells in which the virus multiplies transport the spike protein to the cell surface. From there they are harvested and – after detaching from the surface – spontaneously assemble into nanoparticles of spike proteins. These particles are then used for seeding. This technique of producing genetically modified split vaccines is relatively new, but is already used in established vaccines – for example against hepatitis B or in vaccination against the human papilloma virus.
The advantage of split vaccines over attenuated live vaccines is that they can show the immune system a piece of the real, infectious virus without the vaccinated person being threatened by a live virus. The disadvantage, however, is that these vaccines made from highly purified virus fragments only trigger a slight immune reaction, which is usually not sufficient to build up vaccination protection. To overcome this weakness, split vaccines are used Adjuvanzien added. For example, a traditional adjuvant is aluminum hydroxide. In Nuvaxovid, however, a new type of active enhancer is used, which Novavax developed itself and which has not yet been approved in any other vaccine formulation: “Matrix-M1”. These are nanoparticles made from active ingredients from the Chilean soap bark tree. One vaccine dose of Novaxovid contains five micrograms of antigen and 50 micrograms of the enhancer.
Good antibody response, but not very helpful against omicron
However, the fundamental disadvantage of the split vaccines is an important weakness of Nuvaxovid in protecting against COVID-19: split vaccines do not trigger the formation of so-called cytotoxic T cells. However, this type of T cell is important for a broad immune response, which can hardly compensate for the formation of other T cells. But it is precisely the formation of this special type of T-cell (CD8+ cells), which only matures in the thymus in a complicated training process, that is an important pillar for protection against new virus variants. They form exactly the broad T-cell immunity that allows infection with the different variants of the virus, but still protects against a severe course of the disease. The T-cell immunity elicited by the vector and mRNA vaccines and the heterologous vaccination schemes (i.e. for example: first vaccination with AstraZeneka (vector vaccine), then second and booster vaccination with Comirnaty (mRNA vaccine)).
Like all other approved vaccines against COVID-19, Nuvaxovid was also tested on the basis of the wild type and is just as unsuitable to the heavily modified omicron variant as all other vaccines. Clinical testing shows that it elicits a good antibody response, but that alone is of little use against Omicron.
Novavax trials while the alpha variant was rampant
Nuvaxovid’s approval is based on two large clinical trials involving over 40,000 people. The first study ran in the US and Mexico while the alpha variant circulated. The vaccine showed a week after the second vaccine dose – which was administered 21 days after the first dose – a protective effect against infections of 90.4 percent. In the study, full vaccination even provided 100 percent protection against moderate to severe courses.
The second study was conducted by Novavax in the UK. It brought similar results with an effectiveness of almost 90 percent. During this study, too, the subjects’ immune systems “only” had to fight off the alpha variant.
A further study showed that the protection against the South African beta variant (B.1.351) was significantly lower: Only 60 percent protective effect the vaccine was able to achieve against a symptomatic COVID-19 disease.
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There are currently no reliable statements about how well the vaccine works against the omicron variant – Although Novavax evaluates the results from an ongoing study in the USA and Australia as “encouraging”, although omicron does not play a role in this study setting either. Only Alpha, Beta and Delta circulated in the study group. The aim of the study is to investigate the effectiveness of a third vaccine dose – the booster. As with the other booster vaccinations with mRNA vaccines, the proportion of antibodies against the spike protein increases sharply after a third vaccination. How well the protein vaccine works as a booster in a heterologous vaccination scheme – i.e. after vector or mRNA vaccines – has not been investigated. Nobody knows – yet – whether a Nuvaxovid booster is helpful after a vector or mRNA primary immunization.
Why should you be vaccinated with Novaxovid?
However, the company’s information about the effectiveness of the vaccination, the homologous booster and the connections with the different variants is presented in such a confusing way that even the WHO on their overview page until a few days ago launched that Nuvaxovid works against the omicron variant. This statement has since been corrected.
The question arises: Why should one vaccinate with a vaccine that, due to its basic pharmacological properties, does not support the increasingly important strand of the immune system – T-cell immunity? And which, moreover, only builds up “encouraging” antibody-based protection after three doses? Especially since this protection only takes effect after seven months, when the full tested vaccination cycle of three vaccinations has been completed. It could be interpreted as doubts on the part of the company about the sufficient vaccination protection of its product that the announcement published with the market launch also indicates that Novavax is already working on an adapted vaccine.