The Moderna COVID-19 mRNA vaccine, suggesting an efficacy rate of 94.5%
On November 16, Moderna issued a preliminary data readout out of its COVID-19 vaccine, suggesting an efficacy rate of 94.5%. Like the Pfizer-BioNTech vaccine, it is an mRNA vaccine. Unlike that vaccine, however, the Moderna vaccine is stable at 36 to 46 degrees F, about the temperature of a standard home or medical refrigerator, for up to 30 days and can be stored for up to six months at -4 degrees F. It is expected to go to the FDA for consideration for an EUA within days.
- Type: mRNA
- Doses: 2, 28 Days Apart
- Likely EUA Date: December 10, 2020
- Doses by Year End: 50 Million
- Price: $25-$37 per dose
What is mRNA
Professor Isabelle Bekeredjian-Ding, head of the microbiology division of Germany’s Paul Ehrlich Institut, which provides scientific advice to companies, including CureVac, and who sits on the scientific committee of Europe's Innovative Medicines Initiative, provides some answers.
- mRNA vaccine is the first of its type.
- ‘It's a very unique way of making a vaccine and, so far, no (such) vaccine has been licensed for infectious disease,’ said Prof. Bekeredjian-Ding.
Unlike a normal vaccine, RNA vaccines work by introducing an mRNA sequence (the molecule which tells cells what to build) which is coded for a disease specific antigen, once produced within the body, the antigen is recognized by the immune system, preparing it to fight the real thing.
The University of Cambridge says: "There is still a lot of work to be done before mRNA vaccines can become standard treatments, in the meantime, we need a better understanding of their potential side effects, and more evidence of their long term efficacy."
The CDC's COVID-19 mRNA guidelines say:
Most of what we know about mRNA vaccines comes from work on cancer
Most work on using mRNA to provoke an immune response has so far been focused on cancer, with tumour mRNA being used to help people’s immune systems recognize and respond to the proteins produced by their specific tumors. ‘This technology was very good for the oncology field, because you can develop patient-specific vaccines because every tumor is different,’ said Prof. Bekeredjian-Ding.
Using tumor mRNA in this way activates the body’s T-cells – the part of the acquired immune system that kills cells, which is useful to destroy tumors. It could be important for coronavirus, too. ‘In viral infections, often we know that there is a need for a strong T-cell response because viruses like to hide in cells,’ said Prof. Bekeredjian-Ding. ‘There is a certain hope that, especially in this setting, this could really work … and thereby eliminate … the infected cells from the body.’
But to combat a virus such as SARS-CoV-2, it is likely that a different part of the acquired immune system also needs to be activated – the B cells, which produce antibodies that mark the virus out for destruction by the body. ‘And there is little experience with this (apart from animal infection models), because for the tumour model this was not that relevant.’
There are a lot of unknowns
Because mRNA vaccines are only now beginning to be tested in humans, there are a lot of fairly basic unknowns which can only be answered through human trials. ‘What is really the current challenge, I think, is to understand whether these vaccines will really be able to mount a sufficiently protective immune response in the human and to understand, for example, which quantities of mRNA will be needed to do this,’ said Prof. Bekeredjian-Ding.
Other outstanding questions include whether the proteins that have been chosen for the vaccine are the right ones to prevent a coronavirus infection in the body, how targeted the immune response is to this particular coronavirus, how long any immunity would last, and whether it causes side-effects such as increased inflammatory responses like redness and swelling or, in the worst case, aggravates disease.
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