Novavax Covid vaccine: How does it work? When do we get it? How well does it work against new variants?

At a time when there is very little to celebrate, the initial results from the Novavax vaccine trial are like a ray of brilliant sunshine. But with all large clinical trials, the devil is in the detail.So what do we know about the new vaccine, and what else needs to be addressed before it can go into people’s arms?Is it safe and effective?

Phase I and II trials of the vaccine have answered this question. It’s well tolerated and belongs to a class of vaccines based on a “subunit” of virus protein that has been used widely before.

The interim phase III trial data released yesterday shows the vaccine is very effective - preventing moderate and severe Covid disease in 89% of those on the trial. There was only one case of severe Covid requiring hospitalisation in the trial - and that was in a volunteer who had the placebo vaccine.

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How does it work?

Unlike the new RNA vaccines, or the AstraZeneca/Oxford vaccine which uses a harmless virus to smuggle in RNA from the Covid virus, the Novavax vaccine consists of a piece of the Covid-19 virus itself.

It’s a copy of the virus’ spike protein and how they make it is pretty quirky. It’s artificially grown in moth cells before the “spikes” are embedded in a cylindrical nanoparticle.

To ensure the body mounts an immune response, the vaccine also includes a chemical called an adjuvant, to stimulate the immune system. In the case of this vaccine, it’s a spherical molecule called a saponin extracted from plants.How well does it work against new variants?

The trial of 15,000 people was carried out in seven centres across the UK, of those who got Covid-19 more about half were infected with the new “Kent” variant of the virus.

A separate analysis of those people found 85.6% effective against that strain. A separate analysis of phase II trial data from South Africa found the vaccine was 60% effective there.

It’s a significant finding as 90% of the participants were infected with the strain prevalent in South Africa that is capable of evading antibodies to previous strains of Covid.

The results are important confirmation that the South Africa variant is worrying because it clearly can escape our immune response. But it's also reassuring in that even a vaccine not designed to target it provides a good degree of protection.

Novavax announced yesterday, like other vaccine makers, that it was working on tweaking its designs to work better against new variants.How effective is it in the elderly?

Unlike in trials for the Pfizer/Biontech and Oxford/AstraZeneca vaccines, the Novavax trial included a higher proportion of elderly volunteers. Of the 15,000 studied, 27% were over 65. We don’t yet have data on how well protected they were as a group, but if the overall protection was 89% it’s reasonable to assume protection in the elderly was pretty good.When do we get it?

This is less clear. While the Novavax jab is being produced in the UK, the government has said doses won’t be available until the middle of the year. I understand the reason for this is that Novavax has concentrated on US production as well as expanding its manufacturing across Europe as well.

This has stretched a fairly small drug maker quite thinly, meaning high volume production could still take some time to scale up.

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