I see three "buckets" in the COVID-19 space: vaccines, diagnostics, and treatments. Vaccines have been the big winner so far: One small vaccine company, Novavax (NASDAQ: NVAX) , had an amazing year in which it jumped from $4 per share in January 2020 to $129 in December.
Why have vaccines been the big winner? It's because the market opportunity is so huge -- every human being on the planet could be vaccinated. Healthy people who have no COVID-19 symptoms whatsoever might get a shot.
However, the diagnostic space is smaller. We need diagnostics to distinguish people who have COVID-19 from people with influenza, or the common cold. But the market opportunity is smaller than the vaccine space -- it's mostly for sick people who have symptoms.
For further details see:
Why This COVID-19 Stock Is On Fire Right Now