As promising results are released from a second vaccine trial, we take a look at what this could mean in the battle against Covid-19.
What’s happened?
Early results from phase 3 clinical trials of a Covid-19 vaccine from the US-based company Moderna have been released. These trials are carried out in humans to assess how safe and effective a vaccine is. The Moderna trial involved more than 30,000 participants in the US split into two groups, with one group given two doses of the vaccine and the other group given a placebo.
The new findings are very promising. Based on data from 95 participants with confirmed cases of Covid at least two weeks after the second dose of the vaccine, the researchers report that the vaccine has an efficacy of 94.5%. In other words, 90 of the Covid cases occurred among participants who had been given placebo jabs, with only five cases occurring among those given the vaccine.
When the team analysed the breakdown for 11 severe cases of Covid, they found all had occurred among those who had received the placebo.
In addition, the researchers say the vaccine has not raised any significant safety concerns – the main side effects included pain at the injection site at the first dose, and headache, fatigue and pain in the muscles after the second. “These solicited adverse events were generally short-lived,” the researchers note.
How does this vaccine work?
Like the Pfizer/BioNTech vaccine, which was revealed last week to be 90% effective against Covid, the Moderna vaccine is based on introducing genetic material, known as mRNA, into the human body, which carries instructions for making the “spike proteins” that sit on the outside of the coronavirus and are crucial in allowing the virus to enter human cells.
When this mRNA is introduced to the body, the protein-making machinery within human cells churns out the spike proteins. These proteins are displayed on the outside of the cells, triggering the body’s immune response.
Contrary to claims by some anti-vaxxers, the viral mRNA cannot alter our genes.
Both the Moderna and the Pfizer/BioNTech vaccines involve two doses, spaced a few weeks apart.
How exciting are the new results?
The latest findings will be cause for excitement on several levels. The high efficacy supports the findings from the Pfizer/BioNTech trials, adding further evidence that mRNA vaccines work well against Covid.
The findings also offer evidence that vaccines that trigger an immune response based on the spike proteins work: that is important because several other vaccines in development are also based on this strategy. For example, the AstraZeneca Oxford vaccine uses a chimp cold virus, which has been modified so that it can’t actually cause infection, to deliver the genetic sequence of the coronavirus spike proteins to human cells.
As with the Pfizer/BioNTech jab, the Moderna team are keen to point out that Covid cases were among participants of different ages and ethnicities. That matters because numerous studies have found that people who are older or of particular ethnicities are at greater risk from the disease.
However, as with the results last week, the new findings have not yet been peer-reviewed and the trial is not yet complete. Among outstanding questions, it is not clear how long any protection may last.
And, once again, details remain scarce, meaning it is not clear whether the vaccine prevents people becoming infected with the coronavirus and passing it on, or whether it just prevents people from developing symptoms of Covid. According to the trial protocol, participants had to show symptoms and a positive test results to be deemed a “confirmed case”.
How does the Moderna vaccine differ from the Pfizer/BioNTech vaccine?
While both are based on the same approach, there are some important differences.
In particular, while the Pfizer/BioNTech vaccine must be stored at -80C – a requirement that brings with it serious logistical challenges – researchers say the formulation of the Moderna vaccine means it is stable for 30 days at temperatures between 2C and 8C. That means the vaccine can be stored in a standard refrigerator – a boon when it comes to getting the vaccine to the population.
Should the Moderna vaccine need to be stored for longer, the team say it can last for six months at -20C, while it is stable for up to 12 hours at room temperature.
What happens next?
Moderna says it is planning to apply for an Emergency Use Authorization (EUA) with the US Food and Drug Administration (FDA) in the coming weeks, adding that by the end of the year it expects to have 20m doses of the vaccine ready to ship in the US. Moderna has already begun submitting data to the UK’s Medicines and Healthcare products Regulatory Agency (MHRA).
However, at present the Moderna vaccine is not among the portfolio of different Covid vaccines that the UK has secured doses of, should they be effective.
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