A vaccine from Novavax has been shown to be 89% effective in preventing Covid-19, according to the US biotech firm.
It also remained highly effective against a variant first identified in the UK.
However, it offered significantly less protection against a highly transmissible variant of the coronavirus first identified in South Africa.
How does the vaccine work?
The Novavax vaccine works like other vaccines by teaching the immune system to make antibodies to the coronavirus spike protein.
Researchers inserted a modified gene into a virus, called a baculovirus, and allowed it to infect insect cells.
Spike proteins from these cells were then assembled into nanoparticles which, while they look like coronavirus, cannot replicate or cause Covid-19.
These nanoparticles are then injected into the body via the vaccine where the immune system mounts an antibody response.
If the body encounters coronavirus in the future, the body is primed to fend it off.
Are there advantages of the Novavax vaccine?
Yes. While the jabs from Pfizer/BioNTech and Moderna need to be kept at ultra-low temperatures, the Novavax jab is stable for up to three months in a normal fridge.
The jab should be available in the second half of this year and is being manufactured in the UK.
How was the jab tested?
More than 15,000 people in the UK took part in the clinical trial, which was supported by the UK National Institute for Health Research.
Some 27% of those in the UK were over the age of 65.
The study assessed how effective the vaccine was when transmission of Covid-19 was high in the UK, and with the variant strain identified in the UK circulating widely.
The analysis, based on the first 62 cases of Covid-19 identified in the trial, reported 56 cases in people given a placebo (dummy) vaccine while six cases were in those given the vaccine.
More than 50% of cases related to the UK strain of the virus, with the vaccine offering 86% protection against this strain.
Against the original strain that has circulated since the start of the pandemic, the vaccine was 96% effective.
Novavax COVID-19 Vaccine Demonstrates 89.3% Efficacy in UK Phase 3 Trial https://t.co/8HCAbqIVxH pic.twitter.com/PFaLXkNmA8
— Novavax (@Novavax) January 28, 2021
The vaccine was one of six candidates backed by a US government project formerly known as Operation Warp Speed, which has provided the company $1.75 billion.
It is also being tested in a trial in the US and Mexico, which has recruited 16,000 of 30,000 participants.
What about the South Africa strain?
Data from more than 20,000 people, including a trial in South Africa, has now been reported.
In the South African arm of the trial, where most cases of Covid-19 were the South African strain, the jab was 60% effective in preventing mild, moderate and severe coronavirus among those without HIV.
Including the HIV positive participants, whose immune systems are compromised, overall the protection was just over 49%.
Scientists continue to be concerned about the South African strain of the virus and one that emerged in Brazil, with the expectation that these strains will not work as well with current vaccines.
Novavax plans to immediately begin development on a vaccine specifically targeted to the South African variant.
The studies are the first to assess a Covid-19 vaccine's performance against both the UK and South Africa variants in the real world.
Pfizer and Moderna have previously said their vaccines remain effective against the variants, but their studies were based on lab research.
