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MELBOURNE: The American biotechnology firm Moderna has released the first results of its phase 3 clinical trials, announcing in a press release on Monday (November 17) that its COVID-19 vaccine is 94.5 percent effective, based on an “interim analysis” from an independent security and data monitoring board.
While this is good news, many questions remain.
We do not yet know how long protection against the virus will last with this vaccine. We also don’t know for sure if this vaccine is safe and effective in different types of people, such as pregnant women, the elderly, or people with a chronic disease.
Once a vaccine is implemented “in the real world,” we will begin to understand its true efficacy. In practice, this is likely to differ from its efficacy in highly controlled clinical trials.
So far, we can only say that the Moderna vaccine prevents COVID-19 symptoms, as only volunteers who developed symptoms in this trial were tested. We don’t know for sure if you can prevent infection completely.
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Vaccines that control the symptoms of the disease, rather than prevent infectious viruses from spreading from person to person, are valuable.
But it is vaccines that “block transmission” that are most effective at rapidly reducing viral spread and have the greatest chance of eliminating a pathogen from a population.
THE MODERN CANDIDATE MAY BE EASIER TO TRANSPORT
Like the Pfizer vaccine, Moderna is an mRNA vaccine.
The company is developing it jointly with the National Institute of Allergy and Infectious Diseases, which is part of the US federal health department.
The practical advantage Moderna appears to have over Pfizer is that its temperature requirements for distribution are simpler: 4 degrees Celsius instead of -70 degrees Celsius.
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In this illustration, taken on October 31, 2020, vials with a label that reads “COVID-19 / Coronavirus Vaccine / Injection Only” and a medical syringe are seen in front of the Pfizer logo displayed (File Photo: REUTERS / Given Ruvic).
Storing and transporting a vaccine at 4 degrees Celsius initially, the temperature of a home refrigerator, is much easier. In contrast, -70 degree Celsius freezers can only be found in major hospitals.
For storage longer than 30 days, Moderna vaccine should be kept at -20 degrees Celsius, but even -20 degrees Celsius freezers can be more easily secured.
VARIOUS DEGREES OF EFFECTIVENESS FOR DIFFERENT AGE GROUPS
However, although both vaccines appear to induce neutralizing antibodies against the SARS-CoV-2 “spike protein”, both report relatively poor induction of the other arm of the immune response: the T cells that can attack the virus, particularly those they can do it. after the virus has hidden inside the cells.
What’s more, none of the vaccines have been shown to work as well in older people compared to young adults.
In fact, the first phase 1 and 2 trials of the Pfizer vaccine saw that the vaccine worked half as well in older people for producing antibodies.
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Moderna’s latest human trial evaluating the vaccine’s safety and ability to induce immune responses, which published final results in September after a peer review, showed that its vaccine induced the production of a similar amount of antibodies in adults under 70, compared to those over 70. This is great news.
However, the injection induced significantly fewer T cells in adults older than 71 years, particularly the type of T cells that are expected to be capable of killing virus-infected cells.
So far, it is not known whether this will result in less protection or less sustained immunity, but it is concerning that this vaccine is potentially less effective in older people.
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MANY SUCCESSFUL VACCINES IDEAL
It is great news that several vaccines in development are working well. We now have two COVID mRNA vaccines with a reported efficacy of greater than 90 percent, based on early results from the phase 3 trial.
A man works at the packaging facility of Chinese vaccine manufacturer Sinovac Biotech, developing an experimental vaccine against coronavirus disease (COVID-19), during a government-organized media tour in Beijing, China, on September 24, 2020. (Photo: REUTERS / Thomas Peter)
This opens the door to the possibility that we have many successful vaccines and we can tailor different vaccines to people with different needs.
There are still more than 200 COVID vaccine candidates, many of which use different processes and types of technology. Some of these will work better for different people, for example older people, pregnant women, or people with chronic illnesses.
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For example, “adenovirus” vaccines, of which the University of Oxford vaccine is one, appear to be good at inducing T cells.
And the University of Queensland vaccine appears to be well positioned to induce immune responses specifically in older people.
Tailoring different vaccines to different people will help us increase coverage and hopefully increase the likelihood that we can safely eliminate this virus.
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Magdalena Plebanski is Professor of Immunology, RMIT University. Vasso Apostolopoulos is Professor of Immunology and Associate Vice Chancellor for Research Associations at the University of Victoria. This comment first appeared on The Conversation.
