Pfizer, Moderna, and AstraZeneca. Even though the government has ordered 60m doses of Novavax, most Britons have forgotten about it because they are used to the three Covid vaccines.
A positive decision by UK regulators is anticipated within days or weeks after the US company submitted final data to them. It will bring to an end a long wait that feels like a long time compared to the other jabs.
What difference would this new weapon make to the UK's armoury? Novavax has a vaccine that is similar to those used to protect against flu and is also used for routine childhood vaccinations.
The Covid vaccine is being developed by the two companies with 60 million orders from the UK. The companies will be able to seek regulatory approval once the final data from the trial is available.
Pre-made fragments of the coronaviruses spikeProtein are delivered with the vaccine, compared to the existing UK Covid-19 jabs which instruct our cells to make it.
The Novavax jab has been shown to have an efficacy of about 90% against Covid, similar to the other approved UK vaccines. Preliminary data suggests it creates a robust immune response when given as the second dose.
The signs of reduced side-effects could make Novavax attractive.
Side-effects such as injection-site swelling, fatigue, headaches and muscle pain are less likely to occur if the potential for lower reactogenicity is shown in trial data. Further studies are needed, as no direct head-to-head comparisons have yet been done.
Prof Paul Heath said that lower reactogenicity is important in groups such as children, where the balance between vaccination and not vaccination becomes a little less clear.
Azeem Majeed, professor of primary care and public health at Imperial College London, said that a caveat with any new vaccine is that rarer side-effects may not become apparent until a vaccine is used widely. He said that post-marketing research would be needed to identify any previously unknown side-effects.
It could be more appealing because it uses a more established vaccine technology. It is possible that people who have been hesitant about receiving other Covid vaccines may be more open to receiving a vaccine that uses this technology.
Majeed can see some benefits of such vaccines, but he is less sure about Novavax. It can be stored in a standard vaccine fridge at 2C to 8C, making it easier to transport and store. The UK government seems to have stopped using the Novavax vaccine, despite it having similar storage requirements.
If regular booster shots are needed in the future, access to a broader range of vaccines would be helpful. Majeed said that it would be easier to use in GP surgeries and pharmacies because of Novavax's simpler storage requirements.
In developing countries, where low temperature-controlled supply chains are less well established, the combination of easier transport and storage is even more important. Brendan Wren, professor of microbial pathogenesis at the London School of Hygiene and Tropical Medicine, said that more vaccines are the better if they are low cost and don't require freezing for storage and delivery.
Boris Johnson said in March that 60m doses of the new jab would be made in north-eastern England. The Billingham plant of Fujifilm Diosynth would make them, while the one in Barnard Castle would finish them.
The vaccine was being worked on by about 300 people at FujiFilm, though delays had caused some to worry that jobs would be lost. The company said last month that manufacturing was unaffected by the delay and that it would expand its workforce in the years to come.
Alex Cunningham, the Labour Member of Parliament for Stockton North, met with a representative of Novavax and said he was reassured. He hopes production will get up and running soon, but he doesn't know how long the approvals process will take.
The Novavax jab has been approved in the Philippines and Indonesia. The company submitted an emergency use application to the World Health Organization. It would be the first vaccine to be recommended by the WHO.
Novavax told the Guardian that it was now routinely producing high-quality product at commercial scale at multiple sites across the world. 20m of the 20m approved for export to Indonesia have been manufactured by the Serum Institute of India.
The submission to the UK Medicine and healthcare products Regulatory Authority is complete, and the timelines are in the hands of the regulatory agencies, according to the senior vice-president of global corporate communications and investor relations at Novavax.