The latest share sales by founder Noubar Afeyan and chairman Stephen Hope cast some doubt on this. Even if these sales represent a negligible proportion of their shareholdings, they send out a worrying signal.

In this respect, we note that BioNTech founders Ugur Sahin and Ozlem Tureci - the "Pierre and Marie Curie of the twenty-first century" - and the Struengmann brothers - who still control who still control 44% of the company's capital - are also looking to sell, although again in modest proportions in relation to their shareholdings.

Like BioNTech, Moderna accumulated a vast war chest during the Covid-19 pandemic. The biotech must now use it wisely to finance new R&D programs, which it is actively working on. Meanwhile, its accounts are back in the red, with a loss of $4.7 billion in 2023.

One notable difference between the two companies is that Moderna has significantly less cash than BioNTech - $13 billion for the former, versus $19 billion for the latter. This is due to the fact that the American company spent $6 billion on share buybacks between 2021 and 2023, when its share price was at its highest.

This management decision was therefore questionable, and in fact all the more unpleasant as it was already accompanied by massive share sales by the entire management team. Under these circumstances, it's impossible to let your guard down completely if you're a Moderna shareholder or plan to become one.

This year, the biotech is due to launch its vaccine against respiratory syncytial virus (RSV) and a "new generation" vaccine against Covid; it is also awaiting Phase 3 results for its vaccine against cytomegalovirus (CMV) infection. Although interesting, the rest of the pipeline remains relatively immature.

The Covid franchise is melting like snow in the sun, but should still generate between $3 and $4 billion in revenues by 2024. The RSV vaccine market could reach a peak of $10 billion in sales, but it currently represents a quarter of that, and remains entirely controlled by Pfizer and GSK.

All this has to be set against an enterprise value - market capitalization minus net cash - of $28 billion. What is certain is that Moderna remains valued at an undeniable premium to BioNTech.