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MELBOURNE: American biotech company Moderna released the first results of its Phase 3 clinical trials, announcing in a press release Monday (Nov. 17) that its COVID-19 vaccine is 94.5% effective, according to one. “interim review” by an independent data and safety monitoring committee.
While this is good news, many questions remain.
We still don’t know how long the protection against the virus will last with this vaccine. We also don’t know for sure whether 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 has been distributed “in the real world”, we will begin to understand its true effectiveness. In practice, this is likely to be different from its effectiveness in highly controlled clinical trials.
So far, we can only say that the Moderna vaccine prevents the symptoms of COVID-19, as only the volunteers who developed symptoms in this study were analyzed. We don’t know for sure if it can prevent infection entirely.
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Vaccines that control the symptoms of the disease, rather than preventing the transmission of infectious viruses from person to person, are valuable.
But vaccines that “block transmission” are the most effective in rapidly reducing viral spread and have the highest chance of eliminating a pathogen from a population.
MODERN CANDIDATE MAY BE EASIER TO TRANSPORT
Like Pfizer’s vaccine, Moderna is an mRNA vaccine.
The company is developing it in collaboration with the National Institute of Allergy and Infectious Diseases, part of the U.S. Department of Federal Health.
The practical advantage Moderna appears to have over Pfizer is that its temperature requirements for distribution are simpler: 4 degrees Celsius rather than -70 degrees Celsius.
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Vials with a sticker reading “COVID-19 / Coronavirus Vaccine / Injection Only” and a medical syringe are seen in front of a Pfizer logo displayed in this illustration taken on October 31, 2020 (File Photo: REUTERS / Dado Ruvic)
Storing and transporting a vaccine at 4 degrees Celsius initially, the temperature of a home refrigerator, is much easier. In contrast, freezers at -70 degrees Celsius can only be found in major hospitals.
For storage beyond 30 days the Moderna vaccine should be stored at -20 degrees Celsius, but even freezers at -20 degrees Celsius can be protected more easily.
VARIOUS DEGREES OF EFFECTIVENESS FOR DIFFERENT AGE GROUPS
However, while 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: T cells that can affect the virus, particularly those that they can do this after the virus has hidden inside the cells.
Furthermore, neither vaccine has been shown to work as well in older people as it does in young adults.
As a matter of fact, early Phase 1 and Phase 2 studies of the Pfizer vaccine saw the vaccine give half even in older individuals for antibody production.
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Moderna’s latest human trial evaluating the vaccine’s safety and ability to induce immune responses, which released final results in September after 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 stroke induced significantly fewer T cells in adults over the age of 71, particularly the type of T cells that are predicted to be able to kill virus-infected cells.
So far, it is unknown whether this will result in less protection or less sustained immunity, but it is worrying that this vaccine could potentially be less effective in older people.
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MANY IDEAL SUCCESSFUL VACCINES
It’s great news that more vaccines in the pipeline are showing good results. We now have two mRNA COVID vaccines with reported efficacy greater than 90%, according to the first results of the phase 3 trial.
A man works at the Chinese vaccine manufacturer Sinovac Biotech’s packaging plant, developing an experimental coronavirus (COVID-19) vaccine, during a government-organized media tour in Beijing, China, September 24, 2020 (Photo: REUTERS / Thomas Peter)
This opens the door to the possibility that we may have many successful vaccines and be able to adapt 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 best for different people, for example elderly people, pregnant women or people with chronic diseases.
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For example, “adenovirus” vaccines, one of which is the Oxford University vaccine, appear to be effective in inducing T lymphocytes.
And the University of Queensland vaccine seems well positioned to induce immune responses specifically in older people.
Adapting different vaccines to different people will help us increase coverage and hopefully increase the likelihood of eliminating this virus safely.
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Magdalena Plebanski is Professor of Immunology, RMIT University. Vasso Apostolopoulos is Professor of Immunology and Pro Vice-Chancellor, Research Partnerships, Victoria University. This comment first appeared in The Conversation.
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