Immunity of at least 3 months for Moderna’s vaccine: very preliminary results

The study provides insight into the immune response of Moderna’s mRNA-1273 vaccine. But this stemmed from Phase 1 of the company’s clinical trials. It is very promising, but limited in scope. Here’s what to take away from this study at this stage.

While Pfizer and Moderna recently announced the completion of their Phase 3 and a first authorization has been issued in the UK for Pfizer, the international scientific community is awaiting new publications from both companies, mainly those that are from Phase 3. The problem is that, for the moment, the only data available on this phase come mainly from press releases. As we have pointed out to you for other coronavirus-related issues, it is impossible to draw rigorous conclusions from a press release.

It turns out that on December 3, 2020, The New England Journal of Medicine has published a study of phase 1 of the trials conducted by Moderna, phase that began in March 2020. Therefore, these are not the long-awaited data from phase 3, but they provide some initial information on the duration of the immune response. The results provided in this Moderna vaccine study are promising, validated by an independent review board, but of limited scope.

Here’s what to remember at this point.

The information provided

Alicia T. Widge, immunologist at the National Institute of Allergy and Infectious Diseases, and colleagues conclude that ” these results show that, despite an expected slight decrease in binding and neutralizing antibody titers, mRNA-1273 [nom du vaccin] has the potential to provide long-lasting humoral immunity “.

Data from Moderna’s phase 1 clinical trials show that the immune response against the coronavirus persisted for 3 months after the injections. More specifically, neutralizing antibodies were detected an additional 119 days after the first dose and 90 days after the second dose. This provides an important clue to estimate that the immune response created by Moderna’s vaccine may persist over time.

In some groups, the immune response decreased slightly over the weeks, mainly in the two groups which include the older patients. But this decline was expected and therefore is not a cause for particular concern. In the 34 vaccinated people, the antibody level remained above that found in the control group – 41 people recovered from Covid-19 disease – even after the expected decline.

Another good news that the authors give during their article: no harmful side effects were detected, even after 3 months.

The limits to be clarified

This mainly concerns the antibody response. This is only part of the way the immune response works – the question of T and B lymphocytes remains. The authors claim that ” Studies on vaccine-induced B lymphocytes are ongoing And he specifies that the vaccine would also elicit T helper lymphocyte responses again after 43 days, without providing further details. In concrete terms, this study provides only a partial response to the immune response created by the vaccine.

Furthermore, these are the results of phase 1. This first phase is more limited than the following phases (Moderna’s research has just concluded its phase 3, which is why the authorization process has begun). This means that the data provided in this study is based on a limited sample, as is always the case in phase 1. The results here refer to a sample of 34 adults.

By comparison, in phase 3, more than 30,000 people were involved. The margin is important. However, it is quite logical that in terms of the duration of immunity, the first results come from stage 1: it takes a long time in hindsight to evaluate this duration, and stage 1 goes back several months. The authors also specify that patients will continue to be monitored for 13 months. The same will apply to patients in other stages. And even people who will be vaccinated outside of clinical trials, subject to authorization from independent health authorities, will be subject to pharmacovigilance monitoring to monitor their immunity and side effects.

In conclusion, for this study, the finding of persistence of immunity after 3 months is very promising. However, it should be borne in mind that this result is taken from clinical trials carried out at the beginning of the research phases, on a small number of patients. More significant will be the results of the subsequent phases, conducted on thousands and then tens of thousands of people. As for the decline in the duration of immunity, this will come with time. The short- or medium-term immunity generated by vaccines would already represent a powerful weapon to curb the spread of the coronavirus, even if this would mean, for example, repeating the vaccine seasonally.

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